ZHCS072E March   2011  – November 2015 DAC3484

PRODUCTION DATA.  

  1. 特性
  2. 应用范围
  3. 说明
  4. 修订历史记录
  5. Pin Configuration and Functions
  6. Specifications
    1. 6.1  Absolute Maximum Ratings
    2. 6.2  ESD Ratings
    3. 6.3  Recommended Operating Conditions
    4. 6.4  Thermal InformationZAY package information to Thermal InformationTJ row from top of thermal table
    5. 6.5  Electrical Characteristics - DC Specifications
    6. 6.6  Electrical Characteristics - Digital Specifications
    7. 6.7  Electrical Characteristics - AC Specifications
    8. 6.8  Timing Requirements - Digital Specifications
    9. 6.9  Switching Characteristics - AC Specifications
    10. 6.10 Typical Characteristics
  7. Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1  Serial Interface
      2. 7.3.2  Data Interface
        1. 7.3.2.1 Word-Wide Format
        2. 7.3.2.2 Byte-Wide Format
      3. 7.3.3  Input FIFO
      4. 7.3.4  FIFO Modes of Operation
        1. 7.3.4.1 Dual Sync Sources Mode
        2. 7.3.4.2 Single Sync Source Mode
        3. 7.3.4.3 Bypass Mode
      5. 7.3.5  Clocking Modes
        1. 7.3.5.1 PLL Bypass Mode
        2. 7.3.5.2 PLL Mode
      6. 7.3.6  FIR Filters
      7. 7.3.7  Complex Signal Mixer
        1. 7.3.7.1 Full Complex Mixer
        2. 7.3.7.2 Coarse Complex Mixer
        3. 7.3.7.3 Mixer Gain
        4. 7.3.7.4 Real Channel Upconversion
      8. 7.3.8  Quadrature Modulation Correction (QMC)
        1. 7.3.8.1 Gain and Phase Correction
        2. 7.3.8.2 Offset Correction
        3. 7.3.8.3 Group Delay Correction
      9. 7.3.9  Temperature Sensor
      10. 7.3.10 Data Pattern Checker
      11. 7.3.11 Parity Check Test
        1. 7.3.11.1 Word-by-Word Parity
        2. 7.3.11.2 Block Parity
      12. 7.3.12 DAC3484 Alarm Monitoring
      13. 7.3.13 LVPECL Inputs
      14. 7.3.14 LVDS Inputs
      15. 7.3.15 Unused LVDS Port Termination
      16. 7.3.16 CMOS Digital Inputs
      17. 7.3.17 Reference Operation
      18. 7.3.18 DAC Transfer Function
      19. 7.3.19 Analog Current Outputs
    4. 7.4 Device Functional Modes
      1. 7.4.1 Multi-Device Synchronization
        1. 7.4.1.1 Multi-Device Synchronization: PLL Bypassed with Dual Sync Sources Mode
        2. 7.4.1.2 Multi-Device Synchronization: PLL Enabled with Dual Sync Sources Mode
        3. 7.4.1.3 Multi-Device Operation: Single Sync Source Mode
    5. 7.5 Programming
      1. 7.5.1 Power-Up Sequence
      2. 7.5.2 Example Start-Up Routine
        1. 7.5.2.1 Device Configuration
        2. 7.5.2.2 PLL Configuration
        3. 7.5.2.3 NCO Configuration
        4. 7.5.2.4 Example Start-Up Sequence
    6. 7.6 Register Map
      1. 7.6.1 Register Descriptions
  8. Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Applications
      1. 8.2.1 IF Based LTE Transmitter
        1. 8.2.1.1 Design Requirements
        2. 8.2.1.2 Detailed Design Procedure
          1. 8.2.1.2.1 Data Input Rate
          2. 8.2.1.2.2 Interpolation
          3. 8.2.1.2.3 LO Feedthrough and Sideband Correction
        3. 8.2.1.3 Application Curves
      2. 8.2.2 Direct Upconversion (Zero IF) LTE Transmitter
        1. 8.2.2.1 Design Requirements
        2. 8.2.2.2 Detailed Design Procedure
          1. 8.2.2.2.1 Data Input Rate
          2. 8.2.2.2.2 Interpolation
          3. 8.2.2.2.3 LO Feedthrough and Sideband Correction
        3. 8.2.2.3 Application Curves
  9. Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
      1. 10.1.1 Assembly
    2. 10.2 Layout Examples
  11. 11器件和文档支持
    1. 11.1 器件支持
      1. 11.1.1 Third-Party Products Disclaimer
      2. 11.1.2 器件命名规则
        1. 11.1.2.1 技术参数定义
    2. 11.2 文档支持
      1. 11.2.1 相关文档 
    3. 11.3 社区资源
    4. 11.4 商标
    5. 11.5 静电放电警告
    6. 11.6 Glossary
  12. 12机械、封装和可订购信息

封装选项

机械数据 (封装 | 引脚)
散热焊盘机械数据 (封装 | 引脚)
订购信息

7 Detailed Description

7.1 Overview

The DAC3484 includes a quad-channel, 16-bit digital-to-analog converter (DAC) with up to 1.25 GSPS sample rate, a 16-bit LVDS data bus with on-chip termination, FIFO, data pattern checker, and parity test. The device includes 2x to 16x digital interpolation filters with over 90dB of stop-band attenuation, reconstruction filters, independent complex mixers, a low jitter clock multiplier, and digital Quadrature Modulator Correction (QMC).

Full synchronization of multiple devices is possible with the DAC3484. It is an ideal device for next generation communication systems.

7.2 Functional Block Diagram

DAC3484 B0464-01_LAS749.gif

7.3 Feature Description

7.3.1 Serial Interface

The serial port of the DAC3484 is a flexible serial interface which communicates with industry standard microprocessors and microcontrollers. The interface provides read/write access to all registers used to define the operating modes of DAC3484. It is compatible with most synchronous transfer formats and can be configured as a 3 or 4 pin interface by sif4_ena in register config2. In both configurations, SCLK is the serial interface input clock and SDENB is serial interface enable. For 3 pin configuration, SDIO is a bidirectional pin for both data in and data out. For 4 pin configuration, SDIO is data in only and SDO is data out only. Data is input into the device with the rising edge of SCLK. Data is output from the device on the falling edge of SCLK.

Each read/write operation is framed by signal SDENB (Serial Data Enable Bar) asserted low. The first frame byte is the instruction cycle which identifies the following data transfer cycle as read or write as well as the 7-bit address to be accessed. Table 1 indicates the function of each bit in the instruction cycle and is followed by a detailed description of each bit. The data transfer cycle consists of two bytes.

Table 1. Instruction Byte of the Serial Interface

BIT 7 (MSB) 6 5 4 3 2 1 0 (LSB)
Description R/W A6 A5 A4 A3 A2 A1 A0
R/W Identifies the following data transfer cycle as a read or write operation. A high indicates a read operation from DAC3484 and a low indicates a write operation to DAC3484.
[A6 : A0] Identifies the address of the register to be accessed during the read or write operation.

Figure 50 shows the serial interface timing diagram for a DAC3484 write operation. SCLK is the serial interface clock input to DAC3484. Serial data enable SDENB is an active low input to DAC3484. SDIO is serial data in. Input data to DAC3484 is clocked on the rising edges of SCLK.

DAC3484 T0521-01_LAS748.gif Figure 50. Serial Interface Write Timing Diagram

Figure 51 shows the serial interface timing diagram for a DAC3484 read operation. SCLK is the serial interface clock input to DAC3484. Serial data enable SDENB is an active low input to DAC3484. SDIO is serial data in during the instruction cycle. In 3 pin configuration, SDIO is data out from the DAC3484 during the data transfer cycle, while SDO is in a high-impedance state. In 4 pin configuration, SDO is data out from the DAC3484 during the data transfer cycle. At the end of the data transfer, SDIO and SDO will output low on the final falling edge of SCLK until the rising edge of SDENB when they will 3-state.

DAC3484 T0522-01_LAS748.gif Figure 51. Serial Interface Read Timing Diagram

7.3.2 Data Interface

The DAC3484 has a 16-bit LVDS bus that accepts quad, 16-bit data either in word-wide or dual byte-wide formats. The quad, 16-bit data can be input to the device using either a single-bus, 16-bit interface or a dual-bus, 8-bit interface. The selection between the two modes is done through 16bit_in in the config2 register. The LVDS bus inputs in each mode are shown in Table 2.

Table 2. LVDS Bus Input Assignment

INPUT MODE PINS
Word-wide D[15..0] → Data for paths A, B, C and D
Byte-wide D[15..8] → Data for paths A and B
D[7..0] → Data for paths C and D

Data is sampled by the LVDS double data rate (DDR) clock DATACLK. Setup and hold requirements must be met for proper sampling.

For both input bus modes, a sync signal, either FRAME or SYNC, can sync the FIFO read and/or write pointers. In byte-wide mode the sync source is needed to establish the correct sample boundaries.

The sync signal, either FRAME or SYNC, can be either a pulse or a periodic signal where the sync period corresponds to multiples of 8 samples. FRAME or SYNC is sampled by a rising edge in DATACLK. The pulse-width t(FRAME_SYNC) needs to be at least equal to 1/2 of the DATACLK period.

For both input bus mode, the value in FRAME sampled by the next falling edge in DATACLK can be used as a block parity value. This feature is enabled by setting frame_parity_ena in register config1 to 1b. Refer to Parity Check Test section for more detail

7.3.2.1 Word-Wide Format

The single-bus, 16-bit interface is selected by setting 16bit_in to 1b in the config2 register. In this mode the 16-bit data for channels A, B, C and D is input word-wide interleaved in the form A0, B0, C0, D0, A1… into the D[15:0]P/N LVDS bus. Data into the DAC3484 is formatted according to the diagram shown in Figure 52 where index 0 is the data LSB and index 15 is the data MSB.

DAC3484 T0533-01_LAS749.gif Figure 52. Word-wide Data Transmission Format

7.3.2.2 Byte-Wide Format

The dual-bus, 8-bit interface is selected by setting 16bit_in to 0b in the config2 register. In this mode the 16-bit data for channels A and B is interleaved in the form A0[15:8], A0[7:0], B0[15:8], B0[7:0], A1[15:8]… into the D[15:8]P/N LVDS inputs. Similarly data for channels C and D is interleaved into the D[7:0]P/N LVDS inputs. Data into the DAC3484 is formatted according to the diagram shown in Figure 53 where index 0 is the data LSB and index 15 is the data MSB.

DAC3484 T0534-01_LAS749.gif Figure 53. Byte-wide Data Transmission Format

7.3.3 Input FIFO

The DAC3484 includes a 4-channel, 16-bits wide, and 8-samples deep input FIFO which acts as an elastic buffer. The purpose of the FIFO is to absorb any timing variations between the input data and the internal DAC data rate clock such as the ones resulting from clock-to-data variations from the data source.

Figure 54 shows a simplified block diagram of the FIFO. The following sections provide brief overviews of the FIFO, device synchronization, and device clocking. For more details of the topics, please refer to application note SLAA584.

DAC3484 B0465-01_LAS749.gif Figure 54. DAC3484 FIFO Block Diagram

Data is written to the device 16-bits at a time on the rising and falling edges of DATACLK. In order to form a complete 64-bit wide sample (16-bit A-data, 16-bit B-data, 16-bit C-data, and 16-bit D-data) two DATACLK periods are required. Each 64-bit wide sample is written into the FIFO at the address indicated by the write pointer. Similarly, data from the FIFO is read by the FIFO Out Clock 64-bits at a time from the address indicated by the read pointer. The FIFO Out Clock is generated internally from the DACCLK signal and its rate is equal to DACCLK/Interpolation. Each time a FIFO write or FIFO read is done the corresponding pointer moves to the next address.

The reset position for the FIFO read and write pointers is set by default to addresses 0 and 4 as shown in Figure 54. This offset gives optimal margin within the FIFO. The default read pointer location can be set to another value using fifo_offset(2:0) in register config9 (address 4 by default). Under normal conditions data is written-to and read-from the FIFO at the same rate and consequently the write and read pointer gap remains constant. If the FIFO write and read rates are different, the corresponding pointers will be cycling at different speeds which could result in pointer collision. Under this condition the FIFO attempts to read and write data from the same address at the same time which will result in errors and thus must be avoided.

The write pointer sync source is selected by syncsel_fifoin(3:0) in register config32. In most applications either FRAME or SYNC are used to reset the write pointer. Unlike DATA, the sync signal is latched only on the rising edges of DATACLK. A rising edge on the sync signal source causes the pointer to return to its original position.

Similarly, the read pointer sync source is selected by syncsel_fifoout(3:0). The write pointer sync source can be set to reset the read pointer as well. In this case, FIFO Out clock will recapture the write pointer sync signal to reset the read pointer. This clock domain transfer (DATACLK to FIFO Out Clock) results in phase ambiguity of the reset signal, and will create latency variation based on the capture edge of the FIFO Out Clock. Since the reset signal also synchronizes the clock divider circuit for the FIFO Out Clock generation, the latency variation also includes the capture edge of the DACCLK cycle in the clock divider stage. Ultimately, the variation in capture edge of both the FIFO Out Clock and the DACCLK limits the precise control of the output timing latency. The full latency control of the DAC will be difficult and is not recommended in this setup.

NOTE

For full latency control of the DAC, refer to the Dual Sync Source mode section of the data sheet.

To alleviate this, the device offers the alternative of resetting the FIFO read pointer independently of the write pointer by using the OSTR signal. The OSTR signal is sampled by DACCLK and must satisfy the timing requirements in the specifications table. In order to minimize the skew it is recommended to use the same clock distribution device such as Texas Instruments CDCE62005 or LMK0480x family to provide the DACCLK and OSTR signals to all the DAC3484 devices in the system. Swapping the polarity of the DACCLK outputs with respect to the OSTR ones establishes proper phase relationship.

The FIFO pointers reset procedure can be done periodically or only once during initialization as the pointers automatically return to the initial position when the FIFO has been filled. To reset the FIFO periodically, it is necessary to have the FRAME, SYNC, and OSTR signals to repeat at multiples of 8 FIFO samples. To disable FIFO reset, set syncsel_fifoin(3:0) and syncsel_fifoout(3:0) to 0000b.

The frequency limitation for FRAME and SYNC signals are the following:

fsync = fDATACLK/(n x 16) where n = 1, 2, … for Word-Wide and Byte-Wide Mode

The frequency limitation for the OSTR signal is the following:

fOSTR = fDAC/(n x interpolation x 8) where n = 1, 2, …

The frequencies above are at maximum when n = 1. This is when the FRAME, SYNC, or OSTR have a rising edge transition every 8 FIFO samples. The occurrence can be made less frequent by setting n > 1, for example, every n × 8 FIFO samples.

DAC3484 T0535-01_LAS749.gif Figure 55. FIFO Write and Read Descriptions

7.3.4 FIFO Modes of Operation

The DAC3484 input FIFO can be completely bypassed through registers config0 and config32. The register configuration for each mode is described in Table 3.

Register Control Bits
config0 fifo_ena
config32 syncsel_fifoout(3:0)

Table 3. FIFO Operation Modes

FIFO MODE config0 and config32 FIFO Bits
fifo_ena syncsel_fifoout
BIT 3: sif_sync BIT 2: OSTR BIT 1: FRAME BIT 0: SYNC
Dual Sync Sources 1 0 1 0 0
Single Sync Source 1 0 0 1 or 0 Depends on the sync source 1 or 0 Depends on the sync source
Bypass 0 X X X X

7.3.4.1 Dual Sync Sources Mode

This is the recommended mode of operation for those applications that require precise control of the output timing. In Dual Sync Sources mode, the FIFO write and read pointers are reset independently. The FIFO write pointer is reset using the LVDS FRAME or SYNC signal, and the FIFO read pointer is reset using the LVPECL OSTR signal. This allows LVPECL OSTR signal to control the phase of the output for either a single chip or multiple chips. Multiple devices can be fully synchronized in this mode.

7.3.4.2 Single Sync Source Mode

In Single Sync Source mode, the FIFO write and read pointers are reset from the same source, either LVDS FRAME or LVDS SYNC signal. As described in the Input FIFO section, this mode has latency variations in both the FIFO Out Clock and DAC Clock between the multiple DAC devices. Applications requiring exact output timing control will need Dual Sync Sources mode instead of Single Sync Source Mode. A rising edge for FIFO and clock divider sync is recommended. Periodic sync signal is not recommended due to non-deterministic latency of the sync signal through the clock domain transfer.

7.3.4.3 Bypass Mode

In FIFO bypass mode, the FIFO block is not used. As a result the input data is handed off from the DATACLK to the DACCLK domain without any compensation. In this mode the relationship between DATACLK and DACCLK is critical and used as a synchronizing mechanism for the internal logic. Due to the this constraint this mode is not recommended. The effects of bypassing the FIFO are the following:

  • The FIFO pointers have no effect on the data path or handoff.
  • The FIFO will not be able to pass the controls signals from the LVDS FRAME and LVDS SYNC to digital circuits after the FIFO. These digital circuits mainly are quadrature modulation corrections circuits, complex mixer circuits, and numerical controlled oscillator circuits.

7.3.5 Clocking Modes

The DAC3484 has a dual clock setup in which a DAC clock signal is used to clock the DAC cores and internal digital logic and a separate DATA clock is used to clock the input LVDS receivers and FIFO input. The DAC3484 DAC clock signal can be sourced directly or generated through an on-chip low-jitter phase-locked loop (PLL).

In those applications requiring extremely low noise it is recommended to bypass the PLL and source the DAC clock directly from a high-quality external clock to the DACCLK input. In most applications system clocking can be simplified by using the on-chip PLL to generate the DAC core clock while still satisfying performance requirements. In this case the DACCLK pins are used as the reference frequency input to the PLL.

DAC3484 B0452-01_LAS748.gif Figure 56. Top Level Clock Diagram

7.3.5.1 PLL Bypass Mode

In PLL bypass mode a very high quality clock is sourced to the DACCLK inputs. This clock is used to directly clock the DAC3484 DAC sample rate clock. This mode gives the device best performance and is recommended for extremely demanding applications.

The bypass mode is selected by setting the following:

  1. pll_ena bit in register config24 to 0b to bypass the PLL circuitry.
  2. pll_sleep bit in register config26 to 1b to put the PLL and VCO into sleep mode.

7.3.5.2 PLL Mode

In this mode the clock at the DACCLK input functions as a reference clock source to the on-chip PLL. The on-chip PLL will then multiply this reference clock to supply a higher frequency DAC sample rate clock. Figure 57 shows the block diagram of the PLL circuit.

DAC3484 B0453-01_LAS748.gif Figure 57. PLL Block Diagram

The DAC3484 PLL mode is selected by setting the following:

  1. pll_ena bit in register config24 to 1b to route to the PLL clock path.
  2. pll_sleep bit in register config26 to 0b to enable the PLL and VCO.

The output frequency of the VCO is designed to be the in the range from 3.3GHz to 4.0GHz. The prescaler value, pll_p(2:0) in register config24, should be chosen such that the product of the prescaler value and DAC sample rate clock is within the VCO range. To maintain optimal PLL loop, the coarse tune bits, pll_vco(5:0) in register config26, can adjust the center frequency of the VCO towards the product of the prescaler value and DAC sample rate clock. Figure 58 shows a typical relationship between coarse tune bits and VCO center frequency.

DAC3484 PLL_VCO_Range_vs_Coarse_Tuning_LAS748.gif Figure 58. Typical PLL/VCO Lock Range vs Coarse Tuning Bits

Common wireless infrastructure frequencies (614.4 MHz, 737.28 MHz, 1.2288 GHz, ...) are generated from this VCO frequency in conjunction with the pre-scaler setting as shown in Table 4.

Table 4. VCO Operation

VCO FREQUENCY (MHz) PRE-SCALE DIVIDER DESIRED DACCLK (MHz) pll_p(2:0)
3440.64 7 491.52 111
3686.4 6 614.4 110
3686.4 5 737.28 101
3686.4 3 1228.8 011

The M divider is used to determine the phase-frequency-detector (PFD) and charge-pump (CP) frequency.

Table 5. PFD and CP Operation

DACCLK FREQUENCY (MHz) M DIVIDER PDF UPDATE RATE (MHz) pll_m(7:0)
491.52 4 122.88 00000100
491.52 8 61.44 00001000
491.52 16 30.72 00010000
491.52 32 15.36 00100000

The N divider in the loop allows the PFD to operate at a lower frequency than the reference clock. Both M and N dividers can keep the PFD frequency below 155 MHz for peak operation.

The overall divide ratio inside the loop is the product of the Pre-Scale and M dividers (P * M) and the following guidelines should be followed:

  • The overall divide ratio range is from 24 to 480
  • When the overall divide ratio is less than 120, the internal loop filter can guarantee a stable loop
  • When the overall divide ratio is greater than 120, an external loop filter or double charge pump is required to ensure loop stability

The single- and double-charge-pump current option are selected by setting pll_cp in register config24 to 01b and 11b, respectively. When using the double-charge-pump setting, an external loop filter is not required. If an external filter is required, the following filter should be connected to the LPF pin (A1 for RKD package and D12 for ZAY package):

DAC3484 S0514-01_LAS748.gif Figure 59. Recommended External Loop Filter

The PLL generates an internal OSTR signal and does not require the external LVPECL OSTR signal. The OSTR signal is buffered from the N-divider output in the PLL block, and the frequency of the signal is the same as the PFD frequency. Therefore, using PLL with Dual Sync Sources mode would require the PFD frequency to be the pre-defined OSTR frequency. This will allow the FIFO to be synced correctly by the internal OSTR.

7.3.6 FIR Filters

Figure 60 through Figure 63 show the magnitude spectrum response for the FIR0, FIR1, FIR2 and FIR3 interpolating filters where fIN is the input data rate to the FIR filter. Figure 64 to Figure 67 show the composite filter response for 2x, 4x, 8x and 16x interpolation. The transition band for all interpolation settings is from 0.4 to 0.6 x fDATA (the input data rate to the device) with <0.001dB of pass-band ripple and >90dB stop-band attenuation.

The DAC3484 also has a 9-tap inverse sinc filter (FIR4) that runs at the DAC update rate (fDAC) that can be used to flatten the frequency response of the sample-and-hold output. The DAC sample-and-hold output sets the output current and holds it constant for one DAC clock cycle until the next sample, resulting in the well-known sin(x)/x or sinc(x) frequency response (Figure 68, red line). The inverse sinc filter response (Figure 68, blue line) has the opposite frequency response from 0 to 0.4 x Fdac, resulting in the combined response (Figure 68, green line). Between 0 to 0.4 x fDAC, the inverse sinc filter compensates the sample-and-hold roll-off with less than 0.03dB error.

The inverse sinc filter has a gain >1 at all frequencies. Therefore, the signal input to FIR4 must be reduced from full scale to prevent saturation in the filter. The amount of back-off required depends on the signal frequency, and is set such that at the signal frequencies the combination of the input signal and filter response is less than 1 (0dB). For example, if the signal input to FIR4 is at 0.25 x fDAC, the response of FIR4 is 0.9dB, and the signal must be backed off from full scale by 0.9dB to avoid saturation. The gain function in the QMC blocks can be used to reduce the amplitude of the input signal. The advantage of FIR4 having a positive gain at all frequencies is that the user is then able to optimize the back-off of the signal based on its frequency.

The filter taps for all digital filters are listed in Table 6. Note that the loss of signal amplitude may result in lower SNR due to decrease in signal amplitude.

SPACER

DAC3484 G048_LAS748.gif Figure 60. Magnitude Spectrum for FIR0
SPACER
DAC3484 G050_LAS748.gif Figure 62. Magnitude Spectrum for FIR2
SPACER
DAC3484 G052_LAS748.gif Figure 64. 2x Interpolation Composite Response
SPACER
DAC3484 G054_LAS748.gif Figure 66. 8x Interpolation Composite Response
SPACER
DAC3484 G056_LAS748.gif Figure 68. Magnitude Spectrum for Inverse Sinc Filter
DAC3484 G049_LAS748.gif Figure 61. Magnitude Spectrum for FIR1
SPACER
DAC3484 G051_LAS748.gif Figure 63. Magnitude Spectrum for FIR3
SPACER
DAC3484 G053_LAS748.gif Figure 65. 4x Interpolation Composite Response
SPACER
DAC3484 G055_LAS748.gif Figure 67. 16x Interpolation Composite Response
SPACER

Table 6. FIR Filter Coefficients

INTERPOLATING HALF-BAND FILTERS NON-INTERPOLATING INVERSE-SINC FILTER
FIR0 FIR1 FIR2 FIR3 FIR4
59 TAPS 23 TAPS 11 TAPS 11 TAPS 9 TAPS
6 6 -12 -12 29 29 3 3 1 1
0 0 0 0 0 0 0 0 -4 -4
-19 -19 84 84 -214 -214 -25 -25 13 13
0 0 0 0 0 0 0 0 -50 -50
47 47 -336 -336 1209 1209 150 150 592(1)
0 0 0 0 2048(1) 256(1)
-100 -100 1006 1006
0 0 0 0
192 192 -2691 -2691
0 0 0 0
-342 -342 10141 10141
0 0 16384(1)
572 572
0 0
-914 -914
0 0
1409 1409
0 0
-2119 -2119
0 0
3152 3152
0 0
-4729 -4729
0 0
7420 7420
0 0
-13334 -13334
0 0
41527 41527
65536(1)
(1) Center taps are highlighted in BOLD

7.3.7 Complex Signal Mixer

The DAC3484 has two paths of complex signal mixer blocks that contain two full complex mixer (FMIX) blocks and power saving coarse mixer (CMIX) blocks. The signal path is shown in Figure 69.

DAC3484 B0471-02_LAS749.gif Figure 69. Path of Complex Signal Mixer

7.3.7.1 Full Complex Mixer

The two FMIX blocks operate with independent Numerically Controlled Oscillators (NCOs) and enable flexible frequency placement without imposing additional limitations in the signal bandwidth. The NCOs have 32-bit frequency registers (phaseaddAB(31:0) and phaseaddCD(31:0)) and 16-bit phase registers (phaseoffsetAB(15:0) and phaseoffsetCD(15:0)) that generate the sine and cosine terms for the complex mixing. The NCO block diagram is shown in Figure 70.

DAC3484 B0026-03_LAS748.gif Figure 70. NCO Block Diagram

Synchronization of the NCOs occurs by resetting the NCO accumulators to zero. The synchronization source is selected by syncsel_NCO(3:0) in config31. The frequency word in the phaseaddAB(31:0) and phaseaddCD(31:0) registers is added to the accumulators every clock cycle, fDAC. The output frequency of the NCO is:

Equation 1. DAC3484 EQ_001_LAS748.gif

With the complex mixer enabled, the two channels in the mixer path are treated as complex vectors of the form IIN(t) + j QIN(t). The complex signal multiplier (shown in Figure 71) will multiply the complex channels with the sine and cosine terms generated by the NCO. The resulting output, IOUT(t) + j QOUT(t), of the complex signal multiplier is:

IOUT(t) = (IIN(t)cos(2πfNCOt + δ) – QIN(t)sin(2πfNCOt + δ)) × 2(mixer_gain – 1)

QOUT(t) = (IIN(t)sin(2πfNCOt + δ) + QIN(t)cos(2πfNCOt + δ)) × 2(mixer_gain – 1)

where t is the time since the last resetting of the NCO accumulator, δ is the phase offset value and mixer_gain is either 0 or 1. δ is given by:

δ = 2π × phase_offsetAB/CD(15:0)/216

The mixer_gain option allows the output signals of the multiplier to reduce by half (6dB). See Mixer Gain section for details.

DAC3484 B0472-01_new_LAS748.gif Figure 71. Complex Signal Multiplier

7.3.7.2 Coarse Complex Mixer

In addition to the full complex mixer, the DAC3484 also has a coarse mixer block capable of shifting the input signal spectrum by the fixed mixing frequencies ±n×fS/8. Using the coarse mixer instead of the full mixer lowers power consumption.

The output of the fs/2, fs/4, and –fs/4 mixer block is:

IOUT(t) = I(t)cos(2πfCMIXt) – Q(t)sin(2πfCMIXt)

QOUT(t) = I(t)sin(2πfCMIXt) + Q(t)cos(2πfCMIXt)

Since the sine and the cosine terms are a function of fs/2, fs/4, or –fs/4 mixing frequencies, the possible resulting value of the terms will only be 1, -1, or 0. The simplified mathematics allows the complex signal multiplier to be bypassed in any one of the modes, thus mixer gain is not available. The fs/2, fs/4, and –fs/4 mixer blocks performs mixing through negating and swapping of I/Q channel on certain sequence of samples. Table 7 shows the algorithm used for those mixer blocks.

Table 7. Fs/2, Fs/4, and –Fs/4 Mixing Sequence

MODE MIXING SEQUENCE
Normal (mixer bypassed) Iout = \{+I1, +I2, +I3, +I4…\}
Qout = \{+Q1, +Q2, +Q3, +Q4…\}
fs/2 Iout = \{+I1, -I2, +I3, -I4…\}
Qout = \{+Q1, -Q2, +Q3, -Q4…\}
fs/4 Iout = \{+I1, -Q2, -I3, +Q4…\}
Qout = \{+Q1, +I2, -Q3, -I4…\}
-fs/4 Iout = \{+I1, +Q2, -I3, -Q4…\}
Qout = \{+Q1, -I2, -Q3, +I4…\}

The fs/8 mixer can be enabled along with various combinations of fs/2, fs/4, and –fs/4 mixer. Since the fs/8 mixer uses the complex signal multiplier block with fixed fs/8 sine and cosine term, the output of the multiplier is:

IOUT(t) = (IIN(t)cos(2πfNCOt + δ) – QIN(t)sin(2πfNCOt + δ)) × 2(mixer_gain – 1)

QOUT(t) = (IIN(t)sin(2πfNCOt + δ) + QIN(t)cos(2πfNCOt + δ)) × 2(mixer_gain – 1)

where fCMIX is the fixed mixing frequency selected by cmix(3:0). The mixing combinations are described in Table 8. The mixer_gain option allows the output signals of the multiplier to reduce by half (6dB). See Mixer Gain section for details.

Table 8. Coarse Mixer Combinations

cmix(3:0) Fs/8 MIXER
cmix(3)
Fs/4 MIXER
cmix(2)
Fs/2 MIXER
cmix(1)
–Fs/4 MIXER
cmix(0)
MIXING MODE
0000 Disabled Disabled Disabled Disabled No mixing
0001 Disabled Disabled Disabled Enabled –Fs/4
0010 Disabled Disabled Enabled Disabled Fs/2
0100 Disabled Enabled Disabled Disabled +Fs/4
1000 Enabled Disabled Disabled Disabled +Fs/8
1010 Enabled Disabled Enabled Disabled –3Fs/8
1100 Enabled Enabled Disabled Disabled +3Fs/8
1110 Enabled Enabled Enabled Disabled –Fs/8
All others Not recommended

7.3.7.3 Mixer Gain

The maximum output amplitude out of the complex signal multiplier (i.e., FMIX mode or CMIX mode with fs/8 mixer enabled) occurs if IIN(t) and QIN(t) are simultaneously full scale amplitude and the sine and cosine arguments are equal to 2π x fMIXt + δ (2N-1) x π/4, where N = 1, 2, 3, etc....

DAC3484 M0221-01_LAS748.gif Figure 72. Maximum Output of the Complex Signal Multiplier

With mixer_gain = 1 and both IIN(t) and QIN(t) are simultaneously full scale amplitude, the maximum output possible out of the complex signal multiplier is 0.707 + 0.707 = 1.414 (or 3dB). This configuration can cause clipping of the signal and should therefore be used with caution.

With mixer_gain = 0 in config2, the maximum output possible out of the complex signal multiplier is 0.5 x (0.707 + 0.707) = 0.707 (or -3dB). This loss in signal power is in most cases undesirable, and it is recommended that the gain function of the QMC block be used to increase the signal by 3dB to compensate.

7.3.7.4 Real Channel Upconversion

The mixer in the DAC34H84 treats the A, B, C, and D inputs are complex input data and produces a complex output for most mixing frequencies. The real input data for each channel can be isolated only when the mixing frequency is set to normal mode or fs/2 mode. Refer to Table 7 for details.

7.3.8 Quadrature Modulation Correction (QMC)

7.3.8.1 Gain and Phase Correction

The DAC3484 includes a Quadrature Modulator Correction (QMC) block. The QMC blocks provide a mean for changing the gain and phase of the complex signals to compensate for any I and Q imbalances present in an analog quadrature modulator. The block diagram for the QMC block is shown in Figure 73. The QMC block contains 3 programmable parameters.

Register qmc_gainA/B(10:0) and qmc_gainC/D(10:0) controls the I and Q path gains and is an 11-bit unsigned value with a range of 0 to 1.9990 and the default gain is 1.0000. The implied decimal point for the multiplication is between bit 9 and bit 10.

Register qmc_phaseAB/CD(11:0) control the phase imbalance between I and Q and is a 12-bit values with a range of –0.5 to approximately 0.49975. The QMC phase term is not a direct phase rotation but a constant that is multiplied by each "Q" sample then summed into the "I" sample path. This is an approximation of a true phase rotation in order to keep the implementation simple. The corresponding phase rotation corresponds to approximately +26.5 to –26.5 degrees in 4096 steps.

LO feed-through can be minimized by adjusting the DAC offset feature described below.

DAC3484 B0164-03_LAS751.gif Figure 73. QMC Block Diagram

7.3.8.2 Offset Correction

Registers qmc_offsetA(12:0), qmc_offsetB(12:0), qmc_offsetC(12:0) and qmc_offsetD(12:0) can be used to independently adjust the DC offsets of each channel. The offset values are in represented in 2s-complement format with a range from -4096 to 4095.

The offset value adds a digital offset to the digital data before digital-to-analog conversion. Since the offset is added directly to the data it may be necessary to back off the signal to prevent saturation. Both data and offset values are LSB aligned.

DAC3484 B0165-03_LAS751.gif Figure 74. Digital Offset Block Diagram

7.3.8.3 Group Delay Correction

A complex transmitter system typically is consisted of DACs, reconstruction filter network, and I/Q modulator. Besides the gain and phase mismatch contribution, there could also be timing mismatch contribution from each components. For instance, the timing mismatch could come from the PCB trace length variation between the I and Q channels and the group delay variation from the reconstruction filter.

This timing mismatch in the complex transmitter system creates phase mismatch that varies linearly with respect to frequency. To compensate for the I/Q imbalances due to this mismatch, the DAC3484 has group delay correction block for each DAC channel. Each DAC channel can adjust its delay through grp_delayA(7:0), grp_delayB(7:0), grp_delayC(7:0), and grp_delayD(7:0) in register config46 and config47. The group delay correction, along with gain/phase correction, can be useful for correcting imbalances in wide-band transmitter system. The maximum delay ranges from 30 ps to 100 ps and is dependent on DAC sample clock. Contact TI for specific application information.

7.3.9 Temperature Sensor

The DAC3484 incorporates a temperature sensor block which monitors the temperature by measuring the voltage across 2 transistors. The voltage is converted to an 8-bit digital word using a successive-approximation (SAR) analog to digital conversion process. The result is scaled, limited and formatted as a twos complement value representing the temperature in degrees Celsius.

The sampling is controlled by the serial interface signals SDENB and SCLK. If the temperature sensor is enabled (tsense_sleep = 0b in register config26) a conversion takes place each time the serial port is written or read. The data is only read and sent out by the digital block when the temperature sensor is read in tempdata(7:0) in config6. The conversion uses the first eight clocks of the serial clock as the capture and conversion clock, the data is valid on the falling eighth SCLK. The data is then clocked out of the chip on the rising edge of the ninth SCLK. No other clocks to the chip are necessary for the temperature sensor operation. As a result the temperature sensor is enabled even when the device is in sleep mode.

In order for the process described above to operate properly, the serial port read from config6 must be done with an SCLK period of at least 1 μs. If this is not satisfied the temperature sensor accuracy is greatly reduced.

7.3.10 Data Pattern Checker

The DAC3484 incorporates a simple pattern checker test in order to determine errors in the data interface. The main cause of failures is setup/hold timing issues. The test mode is enabled by asserting iotest_ena in register config1. In test mode the analog outputs are deactivated regardless of the state of TXENABLE or sif_texnable in register config3.

The data pattern key used for the test is 8 words long and is specified by the contents of iotest_pattern[0:7] in registers config37 through config44. The data pattern key can be modified by changing the contents of these registers.

The first word in the test frame is determined by a rising edge transition in FRAME or SYNC, depending on the syncsel_fifoin(4:0) setting in config32. At this transition, the pattern0 word should be input to the data pins. Patterns 1 through 7 should follow sequentially on each edge of DATACLK (rising and falling). The sequence should be repeated until the pattern checker test is disabled by setting iotest_ena back to 0b. It is not necessary to have a rising FRAME or SYNC edge aligned with every pattern0 word, just the first one to mark the beginning of the series.

DAC3484 T0528-01_LAS748.gif Figure 75. IO Pattern Checker Data Transmission Format

The test mode determines if the 16-bit LVDS data D[15:0]P/N of all the patterns were received correctly by comparing the received data against the data pattern key. If any of the 16-bit data D[15:0]P/N were received incorrectly, the corresponding bits in iotest_results(15:0) in register config4 will be set to 1b to indicate bit error location. Furthermore, the error condition will trigger the alarm_from_iotest bit in register config5 to indicate a general error in the data interface. When data pattern checker mode is enabled, this alarm in register config5, bit 7 is the only valid alarm. Other alarms in register config5 are not valid and can be disregarded.

For instance, pattern0 is programmed to the default of 0x7A7A. If the received Pattern 0 is 0x7A7B, then bit 0 in iotest_results(15:0) will be set to 1b to indicate an error in bit 0 location. The alarm_from_iotest will also be set to 1b to report the data transfer error. The user can then narrow down the error from the bit location information and implement the fix accordingly.

The alarms can be cleared by writing 0x0000 to iotest_results(15:0) and 0b to alarm_from_iotest through the serial interface. The serial interface will read back 0s if there are no errors or if the errors are cleared. The corresponding alarm bit will remain a 1b if the errors remain.

It is recommended to enable the pattern checker and then run the pattern sequence for 100 or more complete cycles before clearing the iotest_results(15:0) and alarm_from_iotest. This will eliminate the possibility of false alarms generated during the setup sequence.

Based on the pattern test result, the user can adjust the data source output timing, PCB traces delay, or DAC3484 CONFIG36 LVDS Programmable delay to help optimize the setup and hold time of the transmitter system.

DAC3484 B0457-01_LAS748.gif Figure 76. DAC3484 Pattern Check Block Diagram

7.3.11 Parity Check Test

The DAC3484 has a parity check test that enables continuous validity monitoring of the data received by the DAC. Parity check testing in combination with the data pattern checker offer an excellent solution for detecting board assembly issues due to missing pad connections.

For the parity check test, an extra parity bit is added to the data bits to ensure that the total number of set bits (bits with value 1) is even or odd. This simple scheme is used to detect single or any other odd number of data transfer errors. Parity testing is implemented in the DAC3484 in two ways: word-by-word parity and block parity.

7.3.11.1 Word-by-Word Parity

Word-by-word parity is the easiest mode to implement. In this mode the additional parity bit is sourced to the parity input (PARITYP/N) for each data word transfer into the D[15:0]P/N inputs. This mode is enabled by setting the word_parity_ena bit. The input parity value is defined to be the total number of logic 1s on the 17-bit data bus, the D[15:0]P/N inputs and the PARITYP/N input. This value, the total number of logic 1s, must match the parity test selected in the oddeven_parity bit in register config1.

For example, if the oddeven_parity bit is set to 1b for odd parity, then the number of 1s on the 17-bit data bus should be odd. The DAC will check the data transfer through the parity input. If the data received has odd number of 1s, then the parity is correct. If the data received has even number of 1s, then the parity is incorrect. The corresponding alarm for parity error will be set accordingly.

Figure 77 shows the simple XOR structure used to check word parity. Parity is tested independently for data captured on both rising and falling edges of DATACLK (alarm_rparity and alarm_fparity, respectively). Testing on both edges helps in determining a possible setup/hold issue. Both alarms are captured individually in register config5.

DAC3484 B0458-01_LAS748.gif Figure 77. DAC3484 Word-by-Word Parity Check

7.3.11.2 Block Parity

The block parity method uses the FRAME signal to determine the boundaries of the data block to compute parity. This mode is enabled by setting the frame_parity_ena bit in register config1.

A low-to-high transition of FRAME captured with the DATACLK rising edge determines the end point of the parity block and the beginning of the next one. In this method the parity bit of the completed block corresponds to the FRAME value captured on the DATACLK falling edge right after the STOP/START point.

The input parity value is defined to be the total number of logic 1s in the data block. A logic HIGH captured on the falling edge of DATACLK indicates odd parity or odd number of logic 1s, while a logic LOW indicates even parity or even number of logic 1s. If the expected parity does not match the number of logic 1s in the received data, then alarm_frame_parity in register config5 will be set to 1b. The main advantage of the block parity mode is that there is no need for an additional parity LVDS input.

Since the FRAME signal is used for parity testing in addition to FIFO syncing and frame boundary assignment it is mandatory to take some extra steps to avoid device malfunction. If FRAME is used to reset the FIFO pointers continuously, the block size must be a multiple of 8 samples (each sample corresponding to 16-bits A, B, C and D data). In addition since FRAME is used to establish the frame boundary, the parity block must be aligned with the data frame boundaries.

DAC3484 T0527-02_LAS749.gif

NOTES:

Rising edge of FRAMEP/N indicates the beginning of data block.
Parity bit for the current data block is latched on falling edge of DATACLK after the start point for next data block.
Figure 78. DAC3484 Block Parity Check (Example shown with Word Wide Mode)

7.3.12 DAC3484 Alarm Monitoring

The DAC3484 includes a flexible set of alarm monitoring that can be used to alert of a possible malfunction scenario. All the alarm events can be accessed either through the config5 register or through the ALARM pin. Once an alarm is set, the corresponding alarm bit in register config5 must be reset through the serial interface to allow further testing. The set of alarms includes the following conditions:

Zero check alarm

  • Alarm_from_zerochk. Occurs when the FIFO write pointer has an all zeros pattern. Since the write pointer is a shift register, all zeros will cause the input pointer to be stuck until the next sync event. When this happens a sync to the FIFO block is required.

FIFO alarms

  • alarm_from_fifo. Occurs when there is a collision in the FIFO pointers or a collision event is close.
    • alarm_fifo_2away. Pointers are within two addresses of each other.
    • alarm_fifo_1away. Pointers are within one address of each other.
    • alarm_fifo_collision. Pointers are equal to each other.

Clock alarms

  • clock_gone. Occurs when either the DACCLK or DATACLOCK have been stopped.
    • alarm_dacclk_gone. Occurs when the DACCLK has been stopped.
    • alarm_dataclk_gone. Occurs when the DATACLK has been stopped.

Pattern checker alarm

  • alarm_from_iotest. Occurs when the input data pattern does not match the pattern key.

PLL alarm

  • alarm_from_pll. Occurs when the PLL is out of lock.

Parity alarms

  • alarm_rparity. Occurs when there is a parity error in the data captured by the rising edge of DATACLKP/N. The PARITYP/N input is the parity bit (word-by-word parity test).
  • alarm_fparity. Occurs when there is a parity error in the data captured by the falling edge of DATACLKP/N. The PARITYP/N input is the parity bit (word-by-word parity test).
  • alarm_frame_parity_err. Occurs when there is a frame parity error when using the FRAME as the parity bit (block parity test).

To prevent unexpected DAC outputs from propagating into the transmit channel chain, the clock and alarm_ fifo_collision alarms can be set in config2 to shut-off the DAC output automatically regardless of the state of TXENABLE or sif_txenable.

Alarm monitoring is implemented as follows:

  • Power up the device using the recommended power-up sequence.
  • Clear all the alarms in config5 by setting them to 0.
  • Unmask those alarms that will generate a hardware interrupt through the ALARM pin in config7.
  • Enable automatic DAC shut-off in register config2 if required.
  • In the case of an alarm event, the ALARM pin will trigger. If automatic DAC shut-off has been enabled the DAC outputs will be disabled.
  • Read registers config5 to determine which alarm triggered the ALARM pin.
  • Correct the error condition and re-synchronize the FIFO.
  • Clear the alarms in config5.
  • Re-read config5 to ensure the alarm event has been corrected.
  • Keep clearing and reading config5 until no error is reported.

For details of alarm monitoring function and behavior, refer to SLAA585.

7.3.13 LVPECL Inputs

Figure 79 shows an equivalent circuit for the DAC input clock (DACCLKP/N) and the output strobe clock (OSTRP/N).

DAC3484 S0515-01_LAS748.gif

NOTE:

Input common mode level is internally biased
Figure 79. DACCLKP/N and OSTRP/N Equivalent Input Circuit

Figure 80 shows the preferred configuration for driving the CLKIN/CLKINC input clock with a differential ECL/PECL source.

DAC3484 S0029-02_LAS748.gif

NOTE:

Actual RT value depends on differential clock driver output termination recommendation. It is driver type dependent.
Figure 80. Preferred Clock Input Configuration with a Differential ECL/PECL Clock Source

7.3.14 LVDS Inputs

The D[15:0]P/N, DATACLKP/N, SYNCP/N, PARITYP/N, and FRAMEP/N LVDS pairs have the input configuration shown in Figure 81. Figure 82 shows the typical input levels and common-move voltage used to drive these inputs.

DAC3484 S0516-01_LAS748.gif Figure 81. D[15:0]P/N, DATACLKP/N, FRAMEP/N, SYNCP/N and PARITYP/N LVDS Input Configuration
DAC3484 B0459-03_LAS749.gif Figure 82. LVDS Data Input Levels

Table 9. Example LVDS Data Input Levels

APPLIED VOLTAGES RESULTING DIFFERENTIAL VOLTAGE RESULTING COMMON-MODE VOLTAGE LOGICAL BIT BINARY EQUIVALENT
VA VB VA,B VCOM
1.4 V 1.0 V 400 mV 1.2 V 1
1.0 V 1.4 V -400 mV 0
1.2 V 0.8 V 400 mV 1.0 V 1
0.8 V 1.2 V -400 mV 0

7.3.15 Unused LVDS Port Termination

Depending on the DAC3484 functionality required, additional unused LVDS ports such as FRAMEP/N, SYNCP/N, or PARITYP/N can be left unconnected (floating) or connected to a nominal, differential LVDS active HIGH or active LOW voltage. The usage of these ports depends mainly on the FIFO synchronization settings and parity checking settings. The unused FRAMEP/N, SYNCP/N, or PARITYP/N ports can be connected in parallel with the unused LVDS data port with adjustments to the RSET resistor value.

The following example allows the termination of the unused LVDS ports to a known logic HIGH value. As shown in Figure 83, The design involves the connection to the DIGVDD rail and one RSET resistor to bias the positive terminals of unused LVDS ports to be 1.2 V and negative terminals of unused LVDS ports to 1.0 V. The design keeps the minimum common mode input voltage of the LVDS input to be above 1.0 V, and keeps the differential LVDS voltage to be 200 mV. Since the design expects the differential voltage on the unused ports to be static, the differential LVDS voltage can be as low as 100 mV to maintain a logic HIGH. Refer to Electrical Characteristic – Digital Specifications Table for detail of LVDS Input requirements.

DAC3484 LVDS_ports_slas748.gif Figure 83. Unused LVDS Ports Connected to Static Logic High Differential Voltage
  1. Connect the positive terminals of unused LVDS ports in parallel to DIGVDD supply at 1.2 V nominal. For instance, connect SYNC and PARITY positive pins together to DIGVDD.
  2. Connect the negative terminals of unused LVDS ports in parallel to a RSET resistor to ground.
  3. The REQ value is the equivalent, parallel resistance of the on-chip termination for all the unused LVDS ports. With the SYNC and PARITY ports unused, the REQ is two parallel ZT. Worst case ZT value of 135 Ω is used in the design to account for the lowest possible current IEQ and the worst case common mode on the negative LVDS terminals. Another analysis will be performed with ZT value of 85 Ω for worst case differential LVDS voltages.
  4. With Ohm’s Law, the following equation describes the relationship between RSET and REQ.
  5. Equation 2. DAC3484 EQ002_slas748.gif
  6. With REQ of two parallel, 135 Ω ZT (or 67.5 Ω equivalent), RSET is 332 Ω with standard 1% resistor value. IEQ is approximately 3 mA. The expected voltage at negative terminals of LVDS ports is approximately 1.0 V. The differential LVDS voltage is 200 mV.
  7. With same RSET of 332 Ω, if the REQ has dropped to two parallel, 85 Ω ZT (or 42.5 Ω equivalent), IEQ is approximately 3.2 mA. The expected voltage at negative terminals of LVDS port is approximately 1.06 V. The differential LVDS voltage is 136 mV. As long as the static LVDS differential voltage is above 100 mV, the LVDS port will register a logic HIGH value for the data.

7.3.16 CMOS Digital Inputs

Figure 84 shows a schematic of the equivalent CMOS digital inputs of the DAC3484. SDIO, SCLK, SLEEP and TXENABLE have pull-down resistors while SDENB and RESETB have pull-up resistors internal to the DAC3484. See the specification table for logic thresholds. The pull-up and pull-down circuitry is approximately equivalent to 100kΩ.

DAC3484 S0027-03_LAS748.gif Figure 84. CMOS Digital Equivalent Input

7.3.17 Reference Operation

The DAC3484 uses a bandgap reference and control amplifier for biasing the full-scale output current. The full-scale output current is set by applying an external resistor RBIAS to pin BIASJ. The bias current IBIAS through resistor RBIAS is defined by the on-chip bandgap reference voltage and control amplifier. The default full-scale output current equals 64 times this bias current and can thus be expressed as:

IOUTFS = 64 x IBIAS = 64 x (VEXTIO / RBIAS ) / 2

The DAC3484 has a 4-bit coarse gain control coarse_dac(3:0) in the config3 register. Using gain control, the IOUTFS can be expressed as:

IOUTFS = (coarse_dac + 1)/16 x IBIAS x 64 = (coarse_dac + 1)/16 x (VEXTIO / RBIAS) / 2 x 64

where VEXTIO is the voltage at terminal EXTIO. The bandgap reference voltage delivers an accurate voltage of 1.2 V. This reference is active when extref_ena = 0b in config27. An external decoupling capacitor CEXT of 0.1 µF should be connected externally to terminal EXTIO for compensation. The bandgap reference can additionally be used for external reference operation. In that case, an external buffer with high impedance input should be applied in order to limit the bandgap load current to a maximum of 100 nA. The internal reference can be disabled and overridden by an external reference by setting the extref_ena control bit. Capacitor CEXT may hence be omitted. Terminal EXTIO thus serves as either input or output node.

The full-scale output current can be adjusted from 30 mA down to 10 mA by varying resistor RBIAS or changing the externally applied reference voltage.

NOTE

With internal reference, the minimum Rbias resistor value is 1.28 kΩ. Resistor value below 1.28 kΩ is not recommended since it will program the full-scale current to go above 30mA and potentially damages the device.

7.3.18 DAC Transfer Function

The CMOS DACs consist of a segmented array of PMOS current sources, capable of sourcing a full-scale output current up to 30 mA. Differential current switches direct the current to either one of the complementary output nodes IOUTP or IOUTN. Complementary output currents enable differential operation, thus canceling out common mode noise sources (digital feed-through, on-chip and PCB noise), dc offsets, even order distortion components, and increasing signal output power by a factor of two.

The full-scale output current is set using external resistor RBIAS in combination with an on-chip bandgap voltage reference source (+1.2 V) and control amplifier. Current IBIAS through resistor RBIAS is mirrored internally to provide a maximum full-scale output current equal to 64 times IBIAS.

The relation between IOUTP and IOUTN can be expressed as:

IOUTFS = IOUTP + IOUTN

We will denote current flowing into a node as – current and current flowing out of a node as + current. Since the output stage is a current source the current flows from the IOUTP and IOUTN pins. The output current flow in each pin driving a resistive load can be expressed as:

IOUTP = IOUTFS x CODE / 65536

IOUTN = IOUTFS x (65535 – CODE) / 65536

where CODE is the decimal representation of the DAC data input word

For the case where IOUTP and IOUTN drive resistor loads RL directly, this translates into single ended voltages at IOUTP and IOUTN:

VOUTP = IOUT1 x RL

VOUTN = IOUT2 x RL

Assuming that the data is full scale (65535 in offset binary notation) and the RL is 25 Ω, the differential voltage between pins IOUTP and IOUTN can be expressed as:

VOUTP = 20mA x 25 Ω = 0.5 V

VOUTN = 0mA x 25 Ω = 0 V

VDIFF = VOUTP – VOUTN = 0.5V

Note that care should be taken not to exceed the compliance voltages at node IOUTP and IOUTN, which would lead to increased signal distortion.

7.3.19 Analog Current Outputs

The DAC3484 can be easily configured to drive a doubly terminated 50-Ω cable using a properly selected RF transformer. Figure 85 and Figure 86 show the 50-Ω doubly terminated transformer configuration with 1:1 and 4:1 impedance ratio, respectively. Note that the center tap of the primary input of the transformer has to be grounded to enable a DC current flow. Applying a 20-mA full-scale output current would lead to a 0.5 Vpp for a 1:1 transformer and a 1 Vpp output for a 4:1 transformer. The low dc-impedance between IOUTP or IOUTN and the transformer center tap sets the center of the ac-signal to GND, so the 1 Vpp output for the 4:1 transformer results in an output between –0.5 V and 0.5 V.

DAC3484 S0517-01_LAS748.gif Figure 85. Driving a Doubly terminated 50-Ω Cable Using a 1:1 Impedance Ratio Transformer
DAC3484 S0518-01_LAS748.gif Figure 86. Driving a Doubly Terminated 50-Ω Cable Using a 4:1 Impedance Ratio Transformer

7.4 Device Functional Modes

7.4.1 Multi-Device Synchronization

In various applications, such as multi antenna systems where the various transmit channels information is correlated, it is required that multiple DAC devices are completely synchronized such that their outputs are phase aligned. The DAC3484 architecture supports this mode of operation.

7.4.1.1 Multi-Device Synchronization: PLL Bypassed with Dual Sync Sources Mode

For single or multi-device synchronization it is important that delay differences in the data are absorbed by the device so that latency through the device remains the same. Furthermore, to guarantee that the outputs from each DAC are phase aligned it is necessary that data is read from the FIFO of each device simultaneously. In the DAC3484 this is accomplished by operating the multiple devices in Dual Sync Sources mode. In this mode the additional OSTR signal is required by each DAC3484 to be synchronized.

Data into the device is input as LVDS signals from one or multiple baseband ASICs or FPGAs. Data into the multiple DAC devices can experience different delays due to variations in the digital source output paths or board level wiring. These different delays can be effectively absorbed by the DAC3484 FIFO so that all outputs are phase aligned correctly.

DAC3484 B0454-03_LAS749.gif Figure 87. SynchronizationSystem in Dual Sync Sources Mode with PLL Bypassed

For correct operation both OSTR and DACCLK must be generated from the same clock domain. The OSTR signal is sampled by DACCLK and must satisfy the timing requirements in the specifications table. If the clock generator does not have the ability to delay the DACCLK to meet the OSTR timing requirement, the polarity of the DACCLK outputs can be swapped with respect to the OSTR ones to create 180 degree phase delay of the DACCLK. This may help establish proper setup and hold time requirement of the OSTR signal.

Careful board layout planning must be done to ensure that the DACCLK and OSTR signals are distributed from device to device with the lowest skew possible as this will affect the synchronization process. In order to minimize the skew across devices it is recommended to use the same clock distribution device to provide the DACCLK and OSTR signals to all the DAC devices in the system.

DAC3484 T0526-03_LAS749.gif Figure 88. Timing Diagram for LVPECL Synchronization Signals

The following steps are required to ensure the devices are fully synchronized. The procedure assumes all the DAC3484 devices have a DACCLK and OSTR signal and must be carried out on each device.

  1. Start-up the device as described in the power-up sequence. Set the DAC3484 in Dual Sync Sources mode and select OSTR as the clock divider sync source (clkdiv_sync_sel in register config32).
  2. Sync the clock divider and FIFO pointers.
  3. Verify there are no FIFO alarms either through register config5 or through the ALARM pin.
  4. Disable clock divider sync by setting clkdiv_sync_ena to 0b in register config0.

After these steps all the DAC3484 outputs will be synchronized.

7.4.1.2 Multi-Device Synchronization: PLL Enabled with Dual Sync Sources Mode

The DAC3484 allows exact phase alignment between multiple devices even when operating with the internal PLL clock multiplier. In PLL clock mode, the PLL generates the DAC clock and an internal OSTR signal from the reference clock applied to the DACCLK inputs so there is no need to supply an additional LVPECL OSTR signal.

For this method to operate properly the SYNC signal should be set to reset the PLL N dividers to a known state by setting pll_ndivsync_ena in register config24 to 1b. The SYNC signal resets the PLL N dividers with a rising edge, and the timing relationship ts(SYNC_PLL) and th(SYNC_PLL) are relative to the reference clock presented on the DACCLK pin.

Both SYNC and DACCLK can be set as low frequency signals to greatly simplifying trace routing (SYNC can be just a pulse as a single rising edge is required, if using a periodic signal it is recommended to clear the pll_ndivsync_ena bit after resetting the PLL dividers). Besides the ts(SYNC_PLL) and th(SYNC_PLL) requirement between SYNC and DACCLK, there is no additional required timing relationship between the SYNC and FRAME signals or between DACCLK and DATACLK. The only restriction as in the PLL disabled case is that the DACCLK and SYNC signals are distributed from device to device with the lowest skew possible.

DAC3484 B0455-03_LAS749.gif Figure 89. Synchronization System in Dual Sync Sources Mode with PLL Enabled

The following steps are required to ensure the devices are fully synchronized. The procedure assumes all the DAC3484 devices have a DACCLK and SYNC signal and the following steps must be carried out on each device.

  1. Start-up the device as described in the power-up sequence. Set the DAC3484 in Dual Sync Sources mode and enable SYNC to reset the PLL dividers (set pll_ndivsync_ena in register config24 to 1b).
  2. Reset the PLL dividers with a rising edge on SYNC.
  3. Disable PLL dividers resetting.
  4. Sync the clock divider and FIFO pointers.
  5. Verify there are no FIFO alarms either through register config5 or through the ALARM pin.
  6. Disable clock divider sync by setting clkdiv_sync_ena to 0b in register config0.

After these steps all the DAC3484 outputs will be synchronized.

7.4.1.3 Multi-Device Operation: Single Sync Source Mode

In Single Sync Source mode the FIFO read pointer reset is handoff between the two clock domains (DATACLK and FIFO OUT CLOCK) by simply re-sampling the write pointer reset. Since the two clocks are asynchronous there is a small but distinct possibility of a meta-stability during the pointer handoff. As described in the Input FIFO section, this meta-stable situation can change the latency of the multiple DAC devices by both the FIFO Out clock cycles and DAC clock cycles.

When the PLL is enabled with Single Sync Source mode, the FIFO read pointer is not synchronized by the OSTR signal. Therefore, there is no restriction on the PLL PFD frequency as described in the previous section.

DAC3484 B0456-03_LAS749.gif Figure 90. Multi-Device Operation in Single Sync Source Mode

7.5 Programming

7.5.1 Power-Up Sequence

The following startup sequence is recommended to power-up the DAC3484:

  1. Set TXENABLE low
  2. Supply all 1.2-V voltages (DACVDD, DIGVDD, CLKVDD, and VFUSE) and all 3.3-V voltages (AVDD, IOVDD, and PLLAVDD). The 1.2-V and 3.3-V supplies can be powered up simultaneously or in any order. There are no specific requirements on the ramp rate for the supplies.
  3. Provide all LVPECL inputs: DACCLKP/N and the optional OSTRP/N. These inputs can also be provided after the SIF register programming.
  4. Toggle the RESETB pin for a minimum 25 ns active low pulse width.
  5. Program the SIF registers.
  6. Program fuse_sleep (config27, bit<11>) to put the internal fuses to sleep. To enable dual channel mode, set Config1, bit <8> to 0b and Config16, bit<13:12> to 11b. This dual channel mode is functionally equivalent to the dual channel DAC3484 (channels B and C active). See the DAC3484 SLAS748 datasheet for details.
  7. FIFO configuration needed for synchronization:
    1. Program syncsel_fifoin(3:0) (config32, bits<15:12>) to select the FIFO input pointer sync source.
    2. Program syncsel_fifoout(3:0) (config32, bits<11:8>) to select the FIFO output pointer sync source.
    3. Program syncsel_dataformatter(1:0) (config31, bits<3:2>) to select the FIFO Data Formatter sync source.
  8. Clock divider configuration needed for synchronization:
    1. Program clkdiv_sync_sel (config32, bit<0>) to select the clock divider sync source.
    2. Program clkdiv_sync_ena (config0, bit<2>) to 1b to enable clock divider sync.
    3. For multi-DAC synchronization in PLL mode, program pll_ndivsync_ena (config24, bit<11>) to 1b to synchronize the PLL N-divider.
  9. Provide all LVDS inputs (D[15:0]P/N, DATACLKP/N, FRAMEP/N, SYNCP/N, and PARITYP/N) simultaneously. Synchronize the FIFO and clock divider by providing the pulse or periodic signals needed.
    1. For Single Sync Source Mode where either FRAMEP/N or SYNCP/N is used to sync the FIFO, a single rising edge for FIFO, FIFO data formatter, and clock divider sync is recommended. Periodic sync signal is not recommended due to the non-deterministic latency of the sync signal through the clock domain transfer.
    2. For Dual Sync Sources Mode, both single pulse or periodic sync signals can be used.
    3. For multi-DAC synchronization in PLL mode, the LVDS SYNCP/N signal is used to sync the PLL N-divider and can be sourced from either the FPGA/ASIC pattern generator or clock distribution circuit as long as the t(SYNC_PLL) setup and hold timing requirement is met with respect to the reference clock source at DACCLKP/N pins. The LVDS SYNCP/N signal can be provided at this point.
  10. FIFO and clock divider configurations after all the sync signals have provided the initial sync pulses needed for synchronization:
    1. For Single Sync Source Mode where the clock divider sync source is either FRAMEP/N or SYNCP/N, clock divider syncing may be disabled after DAC3484 initialization and before the data transmission by setting clkdiv_sync_ena (config0, bit <2>) to 0b. This is to prevent accidental syncing of the clock divider when sending FRAMEP/N or SYNCP/N pulse to other digital blocks.
    2. For Dual Sync Sources Mode, where the clock divider sync source is from the OSTR signal (either from external OSTRP/N or internal PLL N divider output), the clock divider syncing may be enabled at all time.
    3. Optionally, to prevent accidental syncing of the FIFO and FIFO data formatter when sending the FRAMEP/N or SYNCP/N pulse to other digital blocks such as NCO, QMC, etc, disable FIFO syncing by setting syncsel_fifoin(3:0) and syncsel_fifoout(3:0) to 0000b after the FIFO input and output pointers are initialized. Also Disable the FIFO data formatter by setting syncsel_dataformatter(1:0) to 10b or 11b. If the FIFO and FIFO data formatter sync remain enabled after initialization, the FRAMEP/N or SYNCP/N pulse must occur in ways to not disturb the FIFO operation. Refer to the INPUT FIFO section for detail.
    4. Disable PLL N-divider syncing by setting pll_ndivsync_ena (config24, bit<11>) to 0b.
  11. Enable transmit of data by asserting the TXENABLE pin or set sif_txenable to 1b.
  12. At any time, if any of the clocks (i.e DATACLK or DACCLK) is lost or a FIFO collision alarm is detected, a complete resynchronization of the DAC is necessary. Set TXENABLE low and repeat steps 7 through 11. Program the FIFO configuration and clock divider configuration per steps 7 and 8 appropriately to accept the new sync pulse or pulses for the synchronization.

7.5.2 Example Start-Up Routine

7.5.2.1 Device Configuration

fDATA = 307.2 MSPS
Interpolation = 4x
Input data = baseband data
fOUT = 122.88 MHz
PLL = Enabled
Full Mixer = Enabled
Dual Sync Sources Mode

7.5.2.2 PLL Configuration

fREFCLK = 614.4 MHz at the DACCLKP/N LVPECL pins
fDACCLK = fDATA x Interpolation = 1228.8 MHz
fVCO = 3 x fDACCLK = 3686.4 MHz (keep fVCO between 3.3 GHz to 4 GHz)
PFD = fOSTR = 38.4 MHz
N = 16, M = 32, P = 3, single charge pump
pll_vco(5:0) = 100100b (36)

7.5.2.3 NCO Configuration

fNCO = 122.88 MHz
fNCO_CLK = 1228.8 MHz
freq = fNCO x 2^32 / 1228.8 = 429496730 = 0x1999999A
phaseaddAB(31:0) or phaseaddCD(31:0) = 0x19999999A
NCO SYNC = rising edge of SYNC

7.5.2.4 Example Start-Up Sequence

Table 10. Example Start-Up Sequence Description

STEP READ/WRITE ADDRESS VALUE DESCRIPTION
1 N/A N/A N/A Set TXENABLE Low
2 N/A N/A N/A Power-up the device
3 N/A N/A N/A Apply LVPECL DACCLKP/N for PLL reference clock
4 N/A N/A N/A Toggle RESETB pin
5 Write 0x00 0xF29F QMC offset and correction enabled, 4x int, FIFO enabled, Alarm enabled, clock divider sync enabled, inverse sinc filter enabled.
6 Write 0x01 0x050E Single parity enabled, FIFO alarms enabled (2 away, 1 away, and collision).
7 Write 0x02 0xF052 Output shut-off when DACCLK gone, DATACLK gone, and FIFO collision. Mixer block with NCO enabled, twos complement. Word Wide Interface.
8 Write 0x03 0xA000 Output current set to 20mAFS with internal reference and 1.28-kΩ RBIAS resistor.
9 Write 0x07 0xD8FF Un-mask FIFO collision, DACCLK-gone, and DATACLK-gone alarms to the Alarm output.
10 Write 0x08 N/A Program the desired channel A QMC offset value. (Causes Auto-Sync for QMC AB-Channels Offset Block)
11 Write 0x09 N/A Program the desired FIFO offset value and channel B QMC offset value.
12 Write 0x0A N/A Program the desired channel C QMC offset value. (Causes Auto-Sync for QMC CD-Channels Offset Block)
13 Write 0x0B N/A Program the desired channel D QMC offset value.
14 Write 0x0C N/A Program the desired channel A QMC gain value.
15 Write 0x0D N/A Coarse mixer mode not used. Program the desired channel B QMC gain value.
16 Write 0x0E N/A Program the desired channel C QMC gain value.
17 Write 0x0F N/A Program the desired channel D QMC gain value.
18 Write 0x10 N/A Program the desired channel AB QMC phase value. (Causes Auto-Sync QMC AB-Channels Correction Block)
19 Write 0x11 N/A Program the desired channel CD QMC phase value. (Causes Auto-Sync for the QMC CD-Channels Correction Block)
20 Write 0x12 N/A Program the desired channel AB NCO phase offset value. (Causes Auto-Sync for Channel AB NCO Mixer)
21 Write 0x13 N/A Program the desired channel CD NCO phase offset value. (Causes Auto-Sync for Channel CD NCO Mixer)
22 Write 0x14 0x999A Program the desired channel AB NCO frequency value
23 Write 0x15 0x1999 Program the desired channel AB NCO frequency value
24 Write 0x16 0x999A Program the desired channel CD NCO frequency value
25 Write 0x17 0x1999 Program the desired channel CD NCO frequency value
26 Write 0x18 0x2C58 PLL enabled, PLL N-dividers sync enabled, single charge pump, prescaler = 3.
27 Write 0x19 0x20F4 M = 32, N = 16, PLL VCO bias tune = 01b
28 Write 0x1A 0x9000 PLL VCO coarse tune = 36
29 Write 0x1B 0x0800 Internal reference
30 Write 0x1E 0x9999 QMC offset AB, QMC offset CD, QMC correction AB, and QMC correction CD can be synced by sif_sync or auto-sync from register write
31 Write 0x1F 0x4440 Mixer AB and CD values synced by SYNCP/N. NCO accumulator synced by SYNCP/N.
32 Write 0x20 0x2400 FIFO Input Pointer Sync Source = ISTR FIFO Output Pointer Sync Source = OSTR (from PLL N-divider output) Clock Divider Sync Source = OSTR
33 N/A N/A N/A Provide all the LVDS DATA and DATACLK Provide rising edge FRAMEP/N and rising edge SYNCP/N to sync the FIFO input pointer and PLL N-dividers.
34 Read 0x18 N/A Read back pll_lfvolt(2:0). If the value is not optimal, adjust pll_vco(5:0) in 0x1A.
35 Write 0x05 0x0000 Clear all alarms in 0x05.
36 Read 0x05 N/A Read back all alarms in 0x05. Check for PLL lock, FIFO collision, DACCLK-gone, DATACLK-gone, etc. Fix the error appropriately. Repeat step 34 and 35 as necessary.
37 Write 0x1F 0x4442 Sync all the QMC blocks using sif_sync. These blocks can also be synced via auto-sync through appropriate register writes.
38 Write 0x00 0xF29B Disable clock divider sync.
39 Write 0x1F 0x4448 Set sif_sync to 0b for the next sif_sync event.
40 Write 0x20 0x0000 Disable FIFO input and output pointer sync.
41 Write 0x18 0x2458 Disable PLL N-dividers sync.
42 N/A N/A N/A Set TXENABLE high. Enable data transmission.

7.6 Register Map

Table 11. Register Map(1)

Name Address Default (MSB)
Bit 15
Bit 14 Bit 13 Bit 12 Bit 11 Bit 10 Bit 9 Bit 8 Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 (LSB)
Bit 0
config0 0x00 0x049C qmc_ offsetAB_ ena qmc_ offsetCD_ ena qmc_
corrAB_
ena
qmc_ corrCD_ ena interp(3:0) fifo_ena reserved reserved alarm_out_ ena alarm_outpol clkdiv_
sync_ ena
invsincAB_
ena
invsincCD_
ena
config1 0x01 0x050E iotest_ena reserved reserved 64cnt_
ena
oddeven_parity word_
parity_
ena
frame_
parity_
ena
quad_ena dacA_ complement dacB_ complement dacC_ complement dacD_ complement alarm_
2away_
ena
alarm_
1away_
ena
alarm_
collision_
ena
reserved
config2 0x02 0x7000 16bit_in dacclk gone_ena dataclk gone_ena collision_ gone_ena reserved reserved reserved reserved sif4_ena mixer_ena mixer_gain nco_ena revbus reserved twos reserved
config3 0x03 0xF000 coarse_dac(3:0) reserved reserved sif_txenable
config4 0x04 NA iotest_results(15:0)
config5 0x05 0x0000 alarm_
from_
zerochk
reserved alarms_from_fifo(2:0) alarm_ dacclk_
gone
alarm_ dataclk_
gone
alarm_
output_
gone
alarm_
from_
iotest
reserved alarm_ from_pll alarm_ rparity alarm_
fparity
alarm_ frame_
parity
reserved reserved
config6 0x06 NA tempdata(7:0) reserved reserved reserved
config7 0x07 0xFFFF alarms_mask(15:0)
config8 0x08 0x0000 reserved reserved reserved qmc_offsetA(12:0)
config9 0x09 0x8000 fifo_offset(2:0) qmc_offsetB(12:0)
config10 0x0A 0x0000 reserved reserved reserved qmc_offsetC(12:0)
config11 0x0B 0x0000 reserved reserved reserved qmc_offsetD(12:0)
config12 0x0C 0x0400 reserved reserved reserved reserved reserved qmc_gainA(10:0)
config13 0x0D 0x0400 cmix(3:0) reserved qmc_gainB(10:0)
config14 0x0E 0x0400 reserved reserved reserved reserved reserved qmc_gainC(10:0)
config15 0x0F 0x0400 output_delayAB (1:0) output_delayCD (1:0) reserved qmc_gainD(10:0)
config16 0x10 0x0000 reserved reserved dual_ena (1:0) qmc_phaseAB(11:0)
config17 0x11 0x0000 reserved reserved reserved reserved qmc_phaseCD(11:0)
config18 0x12 0x0000 phase_offsetAB(15:0)
config19 0x13 0x0000 phase_offsetCD(15:0)
config20 0x14 0x0000 phase_addAB(15:0)
config21 0x15 0x0000 phase_addAB(31:16)
config22 0x16 0x0000 phase_addCD(15:0)
config23 0x17 0x0000 phase_addCD(31:16)
config24 0x18 NA reserved pll_reset pll_ ndivsync_ ena pll_ena reserved pll_cp(1:0) pll_p(2:0) pll_lfvolt(2:0)
config25 0x19 0x0440 pll_m(7:0) pll_n(3:0) pll_vcoitune(2:0) reserved
config26 0x1A 0x0020 pll_vco(5:0) reserved reserved bias_
sleep
tsense_
sleep
pll_sleep clkrecv_
sleep
sleepA sleepB sleepC sleepD
config27 0x1B 0x0000 extref_
ena
reserved reserved reserved fuse_
sleep
reserved reserved reserved reserved reserved reserved
config28 0x1C 0x0000 reserved reserved
config29 0x1D 0x0000 reserved reserved
config30 0x1E 0x1111 syncsel_qmoffsetAB(3:0) syncsel_qmoffsetCD(3:0) syncsel_qmcorrAB(3:0) syncsel_qmcorCD(3:0)
config31 0x1F 0x1140 syncsel_mixerAB(3:0) syncsel_mixerCD(3:0) syncsel_nco(3:0) syncsel_dataformatter sif_sync reserved
config32 0x20 0x2400 syncsel_fifoin(3:0) syncsel_fifoout(3:0) reserved clkdiv_ sync_sel
config33 0x21 0x0000 reserved
config34 0x22 0x1B1B pathA_in_sel(1:0) pathB_in_sel(1:0) pathC_in_sel(1:0) pathD_in_sel(1:0) DACA_out_sel(1:0) DACB_out_sel(1:0) DACC_out_sel(1:0) DACD_out_sel(1:0)
config35 0x23 0xFFFF sleep_cntl(15:0)
config36 0x24 0x0000 datadly(2:0) clkdly(2:0) reserved
config37 0x25 0x7A7A iotest_pattern0
config38 0x26 0xB6B6 iotest_pattern1
config39 0x27 0xEAEA iotest_pattern2
config40 0x28 0x4545 iotest_pattern3
config41 0x29 0x1A1A iotest_pattern4
config42 0x2A 0x1616 iotest_pattern5
config43 0x2B 0xAAAA iotest_pattern6
config44 0x2C 0xC6C6 iotest_pattern7
config45 0x2D 0x0004 reserved ostrtodig_sel ramp_ena reserved sifdac_ena
config46 0x2E 0x0000 grp_delayA(7:0) grp_delayB(7:0)
config47 0x2F 0x0000 grp_delayC(7:0) grp_delayD(7:0)
config48 0x30 0x0000 sifdac(15:0)
version 0x7F 0x540C reserved reserved reserved reserved deviceid(1:0) versionid(2:0)
(1) Unless otherwise noted, all reserved registers should be programmed to default values.

7.6.1 Register Descriptions

Table 12. Register Name: config0 – Address: 0x00, Default: 0x049C

Register Name Address Bit Name Function Default Value
config0 0x00 15 qmc_offsetAB_ena When set, the digital Quadrature Modulator Correction (QMC) offset correction for the AB data path is enabled. 0
14 qmc_offsetCD_ena When set, the digital Quadrature Modulator Correction (QMC) offset correction for the CD data path is enabled. 0
13 qmc_corrAB_ena When set, the QMC phase and gain correction circuitry for the AB data path is enabled. 0
12 qmc_corrCD_ena When set, the QMC phase and gain correction circuitry for the CD data path is enabled. 0
11:8 interp(3:0) These bits define the interpolation factor 0100
interp Interpolation Factor
0000 1x
0001 2x
0010 4x
0100 8x
1000 16x
7 fifo_ena When set, the FIFO is enabled. When the FIFO is disabled, DACCCLKP/N and DATACLKP/N must be aligned (not recommended). 1
6 Reserved Reserved for factory use. 0
5 Reserved Reserved for factory use. 0
4 alarm_out_ena When set, the ALARM pin becomes an output. When cleared, the ALARM pin is 3-stated. 1
3 alarm_out_pol This bit changes the polarity of the ALARM signal.
MM 0: Negative logic
MM 1: Positive logic
1
2 clkdiv_sync_ena When set, enables the syncing of the clock divider using the sync source selected by register config32. The internal divided-down clocks will be phase aligned after syncing. Refer to the Power-Up Sequence section for more detail. 1
1 invsincAB_ena When set, the inverse sinc filter for the AB data is enabled. 0
0 invsincCD_ena When set, the inverse sinc filter for the CD data is enabled. 0

Table 13. Register Name: config1 – Address: 0x01, Default: 0x050E

Register Name Address Bit Name Function Default Value
config1 0x01 15 iotest_ena When set, enables the data pattern checker test. The outputs are deactivated regardless of the state of TXENABLE and sif_txenable. 0
14 Reserved Reserved for factory use. 0
13 Reserved Reserved for factory use. 0
12 64cnt_ena When set, enables resetting of the alarms after 64 good samples with the goal of removing unnecessary errors. For instance, when checking setup/hold through the pattern checker test, there may initially be errors. Setting this bit removes the need for a SIF write to clear the alarm register. 0
11 oddeven_parity Selects between odd and even parity check
MM 0: Even parity
MM 1: Odd parity
0
10 word_parity_ena When set, enables parity checking of each input word using the PARITYP/N parity input. It should match the oddeven_parity register setting. 1
9 frame_parity_ena When set, enables parity checking using the FRAME signal to source the parity bit. 0
8 quad_ena When set, the device is in quad channel mode. To enable the dual channel mode, set Config1, bit <8> to 0b and Config16, bit<13:12> to 11b. This dual channel mode is functionally equivalent to the dual channel DAC3484 (channels B and C active). See the DAC3484 SLAS748 datasheet for details. 1
7 dacA_complement When set, the DACA output is complemented. This allows to effectively change the + and – designations of the LVDS data lines. 0
6 dacB_complement When set, the DACB output is complemented. This allows to effectively change the + and – designations of the LVDS data lines. 0
5 dacC_complement When set, the DACC output is complemented. This allows to effectively change the + and – designations of the LVDS data lines. 0
4 dacD_complement When set, the DACD output is complemented. This allows to effectively change the + and – designations of the LVDS data lines. 0
3 alarm_2away_ena When set, the alarm from the FIFO indicating the write and read pointers being 2 away is enabled. 1
2 alarm_1away_ena When set, the alarm from the FIFO indicating the write and read pointers being 1 away is enabled. 1
1 alarm_collision_ena When set, the alarm from the FIFO indicating a collision between the write and read pointers is enabled. 1
0 Reserved Reserved for factory use. 0

Table 14. Register Name: config2 – Address: 0x02, Default: 0x7000

Register Name Address Bit Name Function Default Value
config2 0x02 15 16bit_in When set, the input interface is set to word-wide mode.
When cleared, the input interface is set to byte-wide mode.
0
14 dacclkgone_ena When set, the DACCLK-gone signal from the clock monitor circuit can be used to shut off the DAC outputs. The corresponding alarms, alarm_dacclk_gone and alarm_output_gone, must not be masked (i.e.Config7, bit <10> and bit <8> must set to 0b). 1
13 dataclkgone_ena When set, the DATACLK-gone signal from the clock monitor circuit can be used to shut off the DAC outputs. The corresponding alarms, alarm_dataclk_gone and alarm_output_gone, must not be masked (i.e.Config7, bit <9> and bit <8> must set to 0b). 1
12 collisiongone_ena When set, the FIFO collision alarms can be used to shut off the DAC outputs. The corresponding alarms, alarm_fifo_collision and alarm_output_gone, must not be masked (i.e.Config7, bit <13> and bit <8> must set to 0b). 1
11 Reserved Reserved for factory use. 0
10 Reserved Reserved for factory use. 0
9 Reserved Reserved for factory use. 0
8 Reserved Reserved for factory use. 0
7 sif4_ena When set, the serial interface (SIF) is a 4 bit interface, otherwise it is a 3-bit interface. 0
6 mixer_ena When set, the mixer block is enabled. 0
5 mixer_gain When set, a 6dB gain is added to the mixer output. 0
4 nco_ena When set, the NCO is enabled. This is not required for coarse mixing. 0
3 revbus When set, the input bits for the data bus are reversed. MSB becomes LSB. 0
2 Reserved Reserved for factory use. 0
1 twos When set, the input data format is expected to be 2s complement. When cleared, the input is expected to be offset-binary. 0
0 Reserved Reserved for factory use. 0

Table 15. Register Name: config3 – Address: 0x03, Default: 0xF000

Register Name Address Bit Name Function Default Value
config3 0x03 15:12 coarse_dac(3:0) Scales the output current in 16 equal steps. DAC3484 I-L_EQ_001_LAS748.gif 1111
11:8 Reserved Reserved for factory use. 0000
7:1 Reserved Reserved for factory use. 0000000
0 sif_txenable When set, the internal value of TXENABLE is set to 1b.
To enable analog output data transmission, set sif_txenable to 1b or pull CMOS TXENABLE pin (A32 for DAC3484IRKD and N9 for DAC3484IZAY) to high. To disable analog output, set sif_txenable to 0b and pull CMOS TXENABLE pin (A32 for DAC3484IRKD and N9 for DAC3484IZAY) to low.
0

Table 16. Register Name: config4 – Address: 0x04, Default: No RESET Value (Write to Clear)

Register Name Address Bit Name Function Default Value
config4 0x04 15:0 iotest_results(15:0) This register is used with pattern checker test enabled (iotest_ena in config1, bit<15> set to 1b). It does not have a default RESET value.
The values of these bits tell which bit in the word failed during the pattern checker test. iotest_results(15:8) correspond to the data bits on D[15:8] and iotest_results(7:0) correspond to the data bits on D[7:0].
No RESET Value

Table 17. Register Name: config5 – Address: 0x05, Default: Setup and Power-Up Conditions Dependent (Write to Clear)

Register Name Address Bit Name Function Default Value
config5 0x05 15 alarm_from_zerochk This alarm indicates the 8-bit FIFO write pointer address has an all zeros patterns. Due to pointer address being a shift register, this is not a valid address and will cause the write pointer to be stuck until the next sync. This error is typically caused by timing error or improper power start-up sequence. If this alarm is asserted, resynchronization of FIFO is necessary. See Power-Up Sequence for more detail. NA
14 Reserved Reserved for factory use. NA
13:11 alarms_from_fifo(2:0) Alarm indicating FIFO pointer collisions and nearness:
MM 000: All fine
MM 001: Pointers are 2 away
MM 01x: Pointers are 1 away
MM 1xx: FIFO pointer collision
If the FIFO pointer collision alarm is set when collisiongone_ena is enabled, the FIFO must be re-synchronized and the bits must be cleared to resume normal operation.
NA
10 alarm_dacclk_gone Alarm indicating the DACCLK has been stopped. If the bit is set when dacclkgone_ena is enabled, the DACCLK must resume and the bit must be cleared to resume normal operation. NA
9 alarm_dataclk_gone Alarm indicating the DATACLK has been stopped. If the bit is set when dataclkgone_ena is enabled, the DATACLK must resume and the bit must be cleared to resume normal operation. NA
8 alarm_output_gone Alarm indicating either alarm_dacclk_gone, alarm_dataclk_gone, or alarm_fifo_collision are asserted. It controls the output. When high it will output 0x8000 for each output connected to the DAC. If the bit is set when dacclkgone_ena, dataclkgone_ena, or collisiongone_ena are enabled, then the corresponding errors must be fixed and the bits must be cleared to resume normal operation. NA
7 alarm_from_iotest Alarm indicating the input data pattern does not match the pattern in the iotest_pattern registers. When data pattern checker mode is enabled, this alarm in register config5, bit7 is the only valid alarm. Other alarms in register config5 are not valid and can be disregarded. NA
6 Reserved Reserved for factory use. NA
5 alarm_from_pll Alarm indicating the PLL has lost lock. For version ID 100b or earlier, alarm_from_PLL may not indicate the correct status of the PLL. Refer to pll_lfvolt(2:0) in register config24 for proper PLL lock indication. NA
4 alarm_rparity Alarm indicating a parity error on data captured on the rising edge of DATACLKP/N. NA
3 alarm_fparity Alarm indicating a parity error on data captured on the falling edge of DATACLKP/N. NA
2 alarm_frame_parity Alarm indicating a parity error when using the FRAME as parity bit. NA
1 Reserved Reserved for factory use. NA
0 Reserved Reserved for factory use. NA

Table 18. Register Name: config6 – Address: 0x06, Default: No RESET Value (Read Only)

Register Name Address Bit Name Function Default Value
config6 0x06 15:8 tempdata(7:0) This is the output from the chip temperature sensor. The value of this register in two’s complement format represents the temperature in degrees Celsius. This register must be read with a minimum SCLK period of 1 μs. No RESET Value
7:2 Reserved Reserved for factory use. 000000
1 Reserved Reserved for factory use. 0
0 Reserved Reserved for factory use. 0

Table 19. Register Name: config7 – Address: 0x07, Default: 0xFFFF

Register Name Address Bit Name Function Default Value
config7 0x07 15:0 alarms_mask(15:0) These bits control the masking of the alarms. (0 = not masked, 1 = masked) 0xFFFF
alarm_mask Alarm that is Masked
15 alarm_from_zerochk
14 not used
13 alarm_fifo_collision
12 alarm_fifo_1away
11 alarm_fifo_2away
10 alarm_dacclk_gone
9 alarm_dataclk_gone
8 alarm_output_gone
7 alarm_from_iotest
6 not used
5 alarm_from_pll
4 alarm_rparity
3 alarm_fparity
2 alarm_frame_parity
1 not used
0 not used

Table 20. Register Name: config8 – Address: 0x08, Default: 0x0000 (Causes Auto-Sync)

Register
Name
Address Bit Name Function Default Value
config8 0x08 15 Reserved Reserved for factory use. 0
14 Reserved Reserved for factory use. 0
13 Reserved Reserved for factory use. 0
12:0 qmc_offsetA(12:0) DACA offset correction. The offset is measured in DAC LSBs. If enabled in config30 writing to this register causes an auto-sync to be generated. This loads the values of the QMC offset registers (config8-config9) into the offset block at the same time. When updating the offset values for AB channel config8 should be written last. Programming config9 will not affect the offset setting. All zeros

Table 21. Register Name: config9 – Address: 0x09, Default: 0x8000

Register
Name
Address Bit Name Function Default Value
config9 0x09 15:13 fifo_offset(2:0) When the sync to the FIFO occurs, this is the value loaded into the FIFO read pointer. With this value the initial difference between write and read pointers can be controlled. This may be helpful in syncing multiple chips or controlling the delay through the device. 100
12:0 qmc_offsetB(12:0) DACB offset correction. The offset is measured in DAC LSBs. All zeros

Table 22. Register Name: config10 – Address: 0x0A, Default: 0x0000 (Causes Auto-Sync)

Register
Name
Address Bit Name Function Default Value
config10 0x0A 15 Reserved Reserved for factory use. 0
14 Reserved Reserved for factory use. 0
13 Reserved Reserved for factory use. 0
12:0 qmc_offsetC(12:0) DACC offset correction. The offset is measured in DAC LSBs. If enabled in config30 writing to this register causes an auto-sync to be generated. This loads the values of the CD-channel QMC offset registers (config10-config11) into the offset block at the same time. When updating the offset values for the CD-channel config10 should be written last. Programming config11 will not affect the offset setting. All zeros

Table 23. Register Name: config11 – Address: 0x0B, Default: 0x0000

Register
Name
Address Bit Name Function Default Value
config11 0x0B 15 Reserved Reserved for factory use. 0
14 Reserved Reserved for factory use. 0
13 Reserved Reserved for factory use. 0
12:0 qmc_offsetD(12:0) DACD offset correction. The offset is measured in DAC LSBs. All zeros

Table 24. Register Name: config12 – Address: 0x0C, Default: 0x0400

Register
Name
Address Bit Name Function Default Value
config12 0x0C 15 Reserved Reserved for factory use. 0
14 Reserved Reserved for factory use. 0
13 Reserved Reserved for factory use. 0
12 Reserved Reserved for factory use. 0
11 Reserved Reserved for factory use. 0
10:0 qmc_gainA(10:0) QMC gain for DACA. The full 11-bit qmc_gainA(10:0) word is formatted as UNSIGNED with a range of 0 to 1.9990. The implied decimal point for the multiplication is between bit 9 and bit 10. 10000000000

Table 25. Register Name: config13 – Address: 0x0D, Default: 0x0400

Register
Name
Address Bit Name Function Default Value
config13 0x0D 15 cmix_mode(3:0) Sets the mixing function of the coarse mixer.
MM Bit 15: Fs/8 mixer
MM Bit 14: Fs/4 mixer
MM Bit 13: Fs/2 mixer
MM Bit 12: -Fs/4 mixer
The various mixers can be combined together to obtain a ±n×Fs/8 total mixing factor.
0000
11 Reserved Reserved for factory use. 0
10:0 qmc_gainB(10:0) QMC gain for DACB. The full 11-bit qmc_gainB(10:0) word is formatted as UNSIGNED with a range of 0 to 1.9990. The implied decimal point for the multiplication is between bit 9 and bit 10. 10000000000

Table 26. Register Name: config14 – Address: 0x0E, Default: 0x0400

Register
Name
Address Bit Name Function Default Value
config14 0x0E 15 Reserved Reserved for factory use. 0
14 Reserved Reserved for factory use. 0
13 Reserved Reserved for factory use. 0
12 Reserved Reserved for factory use. 0
11 Reserved Reserved for factory use. 0
10:0 qmc_gainC(10:0) QMC gain for DACC. The 11-bit qmc_gainC(10:0) word is formatted as UNSIGNED with a range of 0 to 1.9990. The implied decimal point for the multiplication is between bit 9 and bit 10. 10000000000

Table 27. Register Name: config15 – Address: 0x0F, Default: 0x0400

Register
Name
Address Bit Name Function Default Value
config15 0x0F 15:14 output_ delayAB(1:0) Delays the AB data path outputs from 0 to 3 DAC clock cycles. 00
13:12 output_ delayCD(1:0) Delays the CD data path outputs from 0 to 3 DAC clock cycles. 00
11 Reserved Reserved for factory use. 0
10:0 qmc_gainD(10:0) QMC gain for DACD. The full 11-bit qmc_gainD(10:0) word is formatted as UNSIGNED with a range of 0 to 1.9990. The implied decimal point for the multiplication is between bit 9 and bit 10. 10000000000

Table 28. Register Name: config16 – Address: 0x10, Default: 0x0000 (Causes Auto-Sync)

Register
Name
Address Bit Name Function Default Value
config16 0x10 15 Reserved Reserved for factory use. 0
14 Reserved Reserved for factory use. 0
13:12 dual_ena (1:0) To enable the dual channel mode, set Config1, bit <8> to 0b and Config16, bit<13:12> to 11b. This dual channel mode is functionally equivalent to the dual channel DAC3484 (channels B and C active). See the DAC3482 SLAS748 data sheet for details. 0
11:0 qmc_phaseAB(11:0) QMC correction phase for the AB data path. The 12-bit qmc_phaseAB(11:0) word is formatted as 2s complement and scaled to occupy a range of –0.5 to 0.49975 and a default phase correction of 0.00. To accomplish QMC phase correction, this value is multiplied by the current B sample, then summed into the A sample. If enabled in config30 writing to this register causes an auto-sync to be generated. This loads the values of the QMC correction registers (config12, config13, and config16) into the QMC block at the same time. When updating the QMC values for the AB channel config16 should be written last. Programming config12 and config13 will not affect the QMC settings. All zeros

Table 29. Register Name: config17 – Address: 0x11, Default: 0x0000 (Causes Auto-Sync)

Register
Name
Address Bit Name Function Default Value
config17 0x11 15 Reserved Reserved for factory use. 0
14 Reserved Reserved for factory use. 0
13 Reserved Reserved for factory use. 0
12 Reserved Reserved for factory use. 0
11:0 qmc_phaseCD(11:0) QMC correction phase for the CD data path. The 12-bit qmc_phaseCD(11:0) word is formatted as 2s complement and scaled to occupy a range of –0.5 to 0.49975 and a default phase correction of 0.00. To accomplish QMC phase correction, this value is multiplied by the current D sample, then summed into the C sample. If enabled in config30 writing to this register causes an auto-sync to be generated. This loads the values of the CD-channel QMC block registers (config14, config15, and config17) into the QMC block at the same time. When updating the QMC values for the CD-channel config17 should be written last. Programming config14 and config15 will not affect the QMC settings. All zeros

Table 30. Register Name: config18 – Address: 0x12, Default: 0x0000 (Causes Auto-Sync)

Register
Name
Address Bit Name Function Default Value
config18 0x12 15:0 phase_offsetAB(15:0) Phase offset added to the AB data path NCO accumulator before the generation of the SIN and COS values. The phase offset is added to the upper 16 bits of the NCO accumulator results and these 16 bits are used in the sin/cos lookup tables. If enabled in config31 writing to this register causes an auto-sync to be generated. This loads the values of the fine mixer block registers (config18, config20, and config21) at the same time. When updating the mixer values the config18 should be written last. Programming config20 and config21 will not affect the mixer settings. 0x0000

Table 31. Register Name: config19 – Address: 0x13, Default: 0x0000 (Causes Auto-Sync)

Register
Name
Address Bit Name Function Default Value
config19 0x13 15:0 phase_ offsetCD(15:0) Phase offset added to the CD data path NCO accumulator before the generation of the SIN and COS values. The phase offset is added to the upper 16 bits of the NCO accumulator results and these 16 bits are used in the sin/cos lookup tables. If enabled in config31 writing to this register causes an auto-sync to be generated. This loads the values of the CD-channel fine mixer block registers (config19, config22 and config23) at the same time. When updating the mixer values for the CD-channel config19 should be written last. Programming config22 and config23 will not affect the mixer settings. 0x0000

Table 32. Register Name: config20 – Address: 0x14, Default: 0x0000

Register
Name
Address Bit Name Function Default Value
config20 0x14 15:0 phase_ addAB(15:0) The phase_addAB(15:0) value is used to determine the NCO frequency. The 2s complement formatted value can be positive or negative. Each LSB represents Fs/(2^32) frequency step. 0x0000

Table 33. Register Name: config21 – Address: 0x15, Default: 0x0000

Register
Name
Address Bit Name Function Default Value
config21 0x15 15:0 phase_ addAB(31:16) See config20 above. 0x0000

Table 34. Register Name: config22 – Address: 0x16, Default: 0x0000

Register
Name
Address Bit Name Function Default Value
config22 0x16 15:0 phase_ addCD(15:0) The phase_addCD(15:0) value is used to determine the NCO frequency. The 2s complement formatted value can be positive or negative. Each LSB represents Fs/(2^32) frequency step. 0x0000

Table 35. Register Name: config23 – Address: 0x17, Default: 0x0000

Register
Name
Address Bit Name Function Default Value
config23 0x17 15:0 phase_ addCD(31:16) See config22 above. 0x0000

Table 36. Register Name: config24 – Address: 0x18, Default: NA

Register
Name
Address Bit Name Function Default Value
config24 0x18 15:13 Reserved Reserved for factory use. 001
12 pll_reset When set, the PLL loop filter (LPF) is pulled down to 0 V. Toggle from 1b to 0b to restart the PLL if an over-speed lock-up occurs. Over-speed can happen when the process is fast, the supplies are higher than nominal, etc. resulting in the feedback dividers missing a clock. 0
11 pll_ndivsync_ena When set, the LVDS SYNC input is used to sync the PLL N dividers. 1
10 pll_ena When set, the PLL is enabled. When cleared, the PLL is bypassed. 0
9:8 Reserved Reserved for factory use. 00
7:6 pll_cp(1:0) PLL pump charge select
MM 00: No charge pump
MM 01: Single pump charge
MM 10: Not used
MM 11: Dual pump charge
00
5:3 pll_p(2:0) PLL pre-scaler dividing module control.
MM 010: 2
MM 011: 3
MM 100: 4
MM 101: 5
MM 110: 6
MM 111: 7
MM 000: 8
001
2:0 pll_lfvolt(2:0) PLL loop filter voltage. This three bit read-only indicator has step size of 0.4125 V. The entire range covers from 0 V to 3.3 V. The optimal lock range of the PLL will be from 010 to 101 (0.825 V to 2.063 V). Adjust pll_vco(5:0) for optimal lock range. NA

Table 37. Register Name: config25 – Address: 0x19, Default: 0x0440

Register
Name
Address Bit Name Function Default Value
config25 0x19 15:8 pll_m(7:0) M portion of the M/N divider of the PLL. If pll_m<7> = 0, the M divider value has the range of pll_m<6:0>, spanning from 4 to 127. (0, 1, 2, and 3 are not valid.)
If pll_m<7> = 1, the M divider value has the range of 2 × pll_m<6:0>, spanning from 8 to 254. (0, 2, 4, and 6 are not valid. M divider has even values only.)
0x04
7:4 pll_n(3:0) N portion of the M/N divider of the PLL.
MM 0000: 1
MM 0001: 2
MM 0010: 3
MM 0011: 4
MM 0100: 5
MM 0101: 6
MM 0110: 7
MM 0111: 8
MM 1000: 9
MM 1001: 10
MM 1010: 11
MM 1011: 12
MM 1100: 13
MM 1101: 14
MM 1110: 15
MM 1111: 16
0100
3:2 pll_vcoitune(1:0) PLL VCO bias tuning bits. Set to 01b for normal PLL operation. 00
1:0 Reserved Reserved for factory use. 00

Table 38. Register Name: config26 – Address: 0x1A, Default: 0x0020

Register
Name
Address Bit Name Function Default Value
config26 0x1A 15:10 pll_vco(5:0) VCO frequency coarse tuning bits. 000000
9 Reserved Reserved for factory use. 0
8 Reserved Reserved for factory use. 0
7 bias_sleep When set, the bias amplifier is put into sleep mode. 0
6 tsense_sleep Turns off the temperature sensor when asserted. 0
5 pll_sleep When set, the PLL is put into sleep mode. 1
4 clkrecv_sleep When asserted the clock input receiver gets put into sleep mode. This affects the OSTR receiver as well. 0
3 sleepA When set, the DACA is put into sleep mode. 0
2 sleepB When set, the DACB is put into sleep mode. 0
1 sleepC When set, the DACC is put into sleep mode. 0
0 sleepD When set, the DACD is put into sleep mode. 0

Table 39. Register Name: config27 – Address: 0x1B, Default: 0x0000

Register
Name
Address Bit Name Function Default Value
config27 0x1B 15 extref_ena Allows the device to use an external reference or the internal reference.
MM 0: Internal reference
MM 1: External reference
0
14 Reserved Reserved for factory use. 0
13 Reserved Reserved for factory use. 0
12 Reserved Reserved for factory use. 0
11 fuse_sleep Put the fuses to sleep when set high.
If SLEEP pin is set to logic HIGH before and during device power-up and initialization, the fuse_sleep bit in register 0x1B, bit 11 must be written after register 0x23 during device initialization register setup.
Note: Default value is ‘0’. Must be set to ‘1’ for proper operation
0
10 Reserved Reserved for factory use. 0
9 Reserved Reserved for factory use. 0
8 Reserved Reserved for factory use. 0
7 Reserved Reserved for factory use. 0
6 Reserved Reserved for factory use. 0
5:0 atest ATEST mode allows the user to check for the internal die voltages to ensure the supply voltages are within the range. When ATEST mode is programmed, the internal die voltages can be measured at the TXENABLE pin. The TXENABLE pin (A32) must be floating without any pull-up or pull-down resistors.
In ATEST mode, the TXENABLE and sif_txenable logics are bypassed, and output will be active at all time.
000000
Config27, bit<5:0> Description Expected Nominal Voltage
001110 DACA AVSS 0 V
001111 DACA DVDD 1.2 V
010000 DACA AVDD 3.3 V
010110 DACB AVSS 0 V
010111 DACB DVDD 1.2 V
011000 DACB AVDD 3.3 V
011110 DACC AVSS 0 V
011111 DACC DVDD 1.2 V
100000 DACC AVDD 3.3 V
100110 DACD AVSS 0 V
100111 DACD DVDD 1.2 V
101000 DACD AVDD 3.3 V
110000 DIGVDD 1.2 V
000101 CLKVDD 1.2 V

Table 40. Register Name: config28 – Address: 0x1C, Default: 0x0000

Register
Name
Address Bit Name Function Default Value
config28 0x1C 15:8 Reserved Reserved for factory use. 0x00
7:0 Reserved Reserved for factory use. 0x00

Table 41. Register Name: config29 – Address: 0x1D, Default: 0x0000

Register
Name
Address Bit Name Function Default Value
config29 0x1D 15:8 Reserved Reserved for factory use. 0x00
7:0 Reserved Reserved for factory use. 0x00

Table 42. Register Name: config30 – Address: 0x1E, Default: 0x1111

Register
Name
Address Bit Name Function Default Value
config30 0x1E 15:12 syncsel_qmoffsetAB(3:0) Selects the syncing source(s) of the AB data path double buffered QMC offset registers. A 1b in the bit enables the signal as a sync source. More than one sync source is permitted.
MM Bit 15: sif_sync (via config31)
MM Bit 14: SYNC
MM Bit 13: OSTR
MM Bit 12: Auto-sync from register write
0001
11:8 syncsel_ qmoffsetCD(3:0) Selects the syncing source(s) of the CD data path double buffered QMC offset registers. A 1b in the bit enables the signal as a sync source. More than one sync source is permitted.
MM Bit 11: sif_sync (via config31)
MM Bit 10: SYNC
MM Bit 9: OSTR
MM Bit 8: Auto-sync from register write
0001
7:4 syncsel_ qmccorrAB(3:0) Selects the syncing source(s) of the AB data path double buffered QMC correction registers. A ‘1’ in the bit enables the signal as a sync source. More than one sync source is permitted.
MM Bit 7: sif_sync (via config31)
MM Bit 6: SYNC
MM Bit 5: OSTR
MM Bit 4: Auto-sync from register write
0001
3:0 syncsel_ qmccorrCD(3:0) Selects the syncing source(s) of the CD data path double buffered QMC correction registers. A 1b in the bit enables the signal as a sync source. More than one sync source is permitted.
MM Bit 3: sif_sync (via config31)
MM Bit 2: SYNC
MM Bit 1: OSTR
MM Bit 0: Auto-sync from register write
0001

Table 43. Register Name: config31 – Address: 0x1F, Default: 0x1140

Register
Name
Address Bit Name Function Default Value
config31 0x1F 15:12 syncsel_mixerAB(3:0) Selects the syncing source(s) of the AB data path double buffered mixer registers. A 1b in the bit enables the signal as a sync source. More than one sync source is permitted.
MM Bit 15: sif_sync (via config31)
MM Bit 14: SYNC
MM Bit 13: OSTR
MM Bit 12: Auto-sync from register write
0001
11:8 syncsel_ mixerCD(3:0) Selects the syncing source(s) of the CD data path double buffered mixer registers. A 1b in the bit enables the signal as a sync source. More than one sync source is permitted.
MM Bit 11: sif_sync (via config31)
MM Bit 10: SYNC
MM Bit 9: OSTR
MM Bit 8: Auto-sync from register write
0001
7:4 syncsel_nco(3:0) Selects the syncing source(s) of the two NCO accumulators. A 1b in the bit enables the signal as a sync source. More than one sync source is permitted.
MM Bit 7: sif_sync (via config31)
MM Bit 6: SYNC
MM Bit 5: OSTR
MM Bit 4: FRAME
0100
3:2 syncsel_dataformatter(1:0) Selects the syncing source of the data formatter. Unlike the other syncs only one sync source is allowed.
MM 00: FRAME
MM 01: SYNC
MM 10: No sync
MM 11: No sync
00
1 sif_sync SIF created sync signal. Set to 1b to cause a sync and then clear to 0b to remove it. 0
0 Reserved Reserved for factory use. 0

Table 44. Register Name: config32 – Address: 0x20, Default: 0x2400

Register
Name
Address Bit Name Function Default Value
config32 0x20 15:12 syncsel_fifoin(3:0) Selects the syncing source(s) of the FIFO input side. A ‘1’ in the bit enables the signal as a sync source. More than one sync source is permitted.
MM Bit 15: sif_sync (via config31)
MM Bit 14: Always zero
MM Bit 13: FRAME
MM Bit 12: SYNC
0010
11:8 syncsel_fifoout(3:0) Selects the syncing source(s) of the FIFO output side. A 1b in the bit enables the signal as a sync source. More than one sync source is permitted.
MM Bit 11: sif_sync (via config31)
MM Bit 10: OSTR – Dual Sync Sources Mode
MM Bit 9: FRAME – Single Sync Source mode
MM Bit 8: SYNC – Single Sync Source mode
0100
7:1 Reserved Reserved for factory use. 0000
0 clkdiv_sync_sel Selects the signal source for clock divider synchronization. 0
clkdiv_sync_sel Sync Source
0 OSTR
1 FRAME or SYNC, based on syncsel_fifoin source selection (config32, bit<15:12>)

Table 45. Register Name: config33 – Address: 0x21, Default: 0x0000

Register
Name
Address Bit Name Function Default Value
config33 0x21 15:0 Reserved Reserved for factory use. 0x0000

Table 46. Register Name: config34 – Address: 0x22, Default: 0x1B1B

Register
Name
Address Bit Name Function Default Value
config34 0x22 15:14 pathA_in_sel(1:0) Selects the word used for the A channel path. 00
13:12 pathB_in_sel(1:0) Selects the word used for the B channel path. 01
11:10 pathC_in_sel(1:0) Selects the word used for the C channel path. 10
9:8 pathD_in_sel(1:0) Selects the word used for the D channel path. 11
7:6 DACA_out_sel(1:0) Selects the word used for the DACA output. 00
5:4 DACB_out_sel(1:0) Selects the word used for the DACB output. 01
3:2 DACC_out_sel(1:0) Selects the word used for the DACC output. 10
1:0 DACD_out_sel(1:0) Selects the word used for the DACD output. 11

Table 47. Register Name: config35 – Address: 0x23, Default: 0xFFFF

Register
Name
Address Bit Name Function Default Value
config35 0x23 15:0 sleep_cntl(15:0) Controls the routing of the CMOS SLEEP signal (pin B40 for the DAC3484IRKD and pin B8 for the DAC3484IZAY) to different blocks. When a bit in this register is set, the SLEEP signal will be sent to the corresponding block. The block will only be disabled when the SLEEP is logic HIGH and the correspond bit is set to 1b. 0xFFFF
These bits do not override SIF bits in config26 that control the same sleep function.
sleep_cntl(bit) Function
15 DACA sleep
14 DACB sleep
13 DACC sleep
12 DACD sleep
11 Clock receiver sleep
10 PLL sleep
9 LVDS data sleep
8 LVDS control sleep
7 Temp sensor sleep
6 reserved
5 Bias amplifier sleep
All others not used

Table 48. Register Name: config36 – Address: 0x24, Default: 0x0000

Register
Name
Address Bit Name Function Default Value
config36 0x24 15:13 datadly(2:0) Controls the delay of the data inputs through the LVDS receivers. Each LSB adds approximately 50 ps. Refer to Digital Input Timing Specifications Table for details.
MM 0: Minimum
000
12:10 clkdly(2:0) Controls the delay of the data clock through the LVDS receivers. Each LSB adds approximately 50 ps. Refer to Digital Input Timing Specifications Table for details.
MM 0: Minimum
000
9:0 Reserved Reserved for factory use. 0x000

Table 49. Register Name: config37 – Address: 0x25, Default: 0x7A7A

Register
Name
Address Bit Name Function Default Value
config37 0x25 15:0 iotest_pattern0 Dataword0 in the IO test pattern. It is used with the seven other words to test the input data.
At the start of the IO test pattern, this word should be aligned with rising edge of FRAME or SYNC signal to indicate sample 0.
0x7A7A

Table 50. Register Name: config38 – Address: 0x26, Default: 0xB6B6

Register
Name
Address Bit Name Function Default Value
config38 0x26 15:0 iotest_pattern1 Dataword1 in the IO test pattern. It is used with the seven other words to test the input data. 0xB6B6

Table 51. Register Name: config39 – Address: 0x27, Default: 0xEAEA

Register
Name
Address Bit Name Function Default Value
config39 0x27 15:0 iotest_pattern2 Dataword2 in the IO test pattern. It is used with the seven other words to test the input data. 0xEAEA

Table 52. Register Name: config40 – Address: 0x28, Default: 0x4545

Register
Name
Address Bit Name Function Default Value
config40 0x28 15:0 iotest_pattern3 Dataword3 in the IO test pattern. It is used with the seven other words to test the input data. 0x4545

Table 53. Register Name: config41 – Address: 0x29, Default: 0x1A1A

Register
Name
Address Bit Name Function Default Value
config41 0x29 15:0 iotest_pattern4 Dataword4 in the IO test pattern. It is used with the seven other words to test the input data. 0x1A1A

Table 54. Register Name: config42 – Address: 0x2A, Default: 0x1616

Register
Name
Address Bit Name Function Default Value
config42 0x2A 15:0 iotest_pattern5 Dataword5 in the IO test pattern. It is used with the seven other words to test the input data. 0x1616

Table 55. Register Name: config43 – Address: 0x2B, Default: 0xAAAA

Register
Name
Address Bit Name Function Default Value
config43 0x2B 15:0 iotest_pattern6 Dataword6 in the IO test pattern. It is used with the seven other words to test the input data. 0xAAAA

Table 56. Register Name: config44 – Address: 0x2C, Default: 0xC6C6

Register
Name
Address Bit Name Function Default Value
config44 0x2C 15:0 iotest_pattern7 Dataword7 in the IO test pattern. It is used with the seven other words to test the input data. 0xC6C6

Table 57. Register Name: config45 – Address: 0x2D, Default: 0x0004

Register
Name
Address Bit Name Function Default Value
config45 0x2D 15 reserved Reserved for factory use 0
14 ostrtodig_sel When set, the OSTR signal is passed directly to the digital block. This is the signal that is used to clock the dividers. 0
13 ramp_ena When set, a ramp signal is inserted in the input data at the FIFO input. 0
12:1 Reserved Reserved for factory use. 0000
0000
0010
0 sifdac_ena When set, the DAC output is set to the value in sifdac(15:0) in register config48. In this mode, sif_txena in config3 and TXENABLE inputs are ignored. 0

Table 58. Register Name: config46 – Address: 0x2E, Default: 0x0000

Register
Name
Address Bit Name Function Default Value
config46 0x2E 15:8 grp_delayA(7:0) Sets the group delay function for DACA. The maximum delay ranges from 30 ps to 100 ps and is dependent on DAC sample clock. Contact TI for specific application information. 0x00
7:0 grp_delayB(7:0) Sets the group delay function for DACB. The maximum delay ranges from 30 ps to 100 ps and is dependent on DAC sample clock. Contact TI for specific application information. 0x00

Table 59. Register Name: config47 – Address: 0x2F, Default: 0x0000

Register
Name
Address Bit Name Function Default Value
config47 0x2F 15:8 grp_delayC(7:0) Sets the group delay function for DACC. The maximum delay ranges from 30 ps to 100 ps and is dependent on DAC sample clock. Contact TI for specific application information. 0x00
7:0 grp_delayD(7:0) Sets the group delay function for DACD. The maximum delay ranges from 30 ps to 100 ps and is dependent on DAC sample clock. Contact TI for specific application information. 0x00

Table 60. Register Name: config48 – Address: 0x30, Default: 0x0000

Register
Name
Address Bit Name Function Default Value
config48 0x30 15:0 sifdac(15:0) Value sent to the DACs when sifdac_ena is asserted. DATACLK must be running to latch this value into the DACs. The format would be based on twos in register config2. 0x0000

Table 61. Register Name: Version – Address: 0x7F, Default: 0x540C (Read Only)

Register
Name
Address Bit Name Function Default Value
version 0x7F 15:10 Reserved Reserved for factory use. 010101
9 Reserved Reserved for factory use. 0
8:7 Reserved Reserved for factory use. 00
6:5 Reserved Reserved for factory use. 00
4:3 deviceid(1:0) Returns 01b for DAC3484. 01
2:0 versionid(2:0) A hardwired register that contains the version of the chip. 100