ADS7049-Q1 器件是一款符合汽车类 Q100 标准的 12 位、2MSPS 模数转换器 (ADC)。此器件支持宽范围的模拟输入电压(2.35V 至 3.6V),并且包括一个基于电容器且内置采样保持电路的 SAR ADC。串行外设接口 (SPI) 兼容串口由 CS 和 SCLK 信号控制。输入信号在 CS 下降沿进行采样,SCLK 用于转换和串行数据输出。此器件支持宽范围的数字电源(1.65V 至 3.6V),可直接连接到各类主机控制器。ADS7049-Q1 符合 JESD8-7A 标准的标称 DVDD 范围(1.65V 至 1.95V)。
ADS7049-Q1 采用 8 引脚微型 VSSOP 封装,额定工作温度范围为 –40°C 至 +125°C。ADS7049-Q1 采样速率较快,采用微型封装并具有低功耗特性,适用于空间受限的汽车类快速扫描 应用。
部件名称 | 封装 | 封装尺寸(标称值) |
---|---|---|
ADS7049-Q1 | 超薄小外形尺寸封装 (VSSOP)(8) | 2.30mm x 2.00mm |
日期 | 修订版本 | 注释 |
---|---|---|
2016 年 11 月 | * | 最初发布。 |
NAME | NO. | I/O | DESCRIPTION |
---|---|---|---|
AINM | 5 | Analog input | Analog signal input, negative |
AINP | 6 | Analog input | Analog signal input, positive |
AVDD | 7 | Supply | Analog power-supply input, also provides the reference voltage to the ADC |
CS | 4 | Digital input | Chip-select signal, active low |
DVDD | 1 | Supply | Digital I/O supply voltage |
GND | 8 | Supply | Ground for power supply, all analog and digital signals are referred to this pin |
SCLK | 2 | Digital input | Serial clock |
SDO | 3 | Digital output | Serial data out |
MIN | MAX | UNIT | |
---|---|---|---|
AVDD to GND | –0.3 | 3.9 | V |
DVDD to GND | –0.3 | 3.9 | V |
AINP to GND | –0.3 | AVDD + 0.3 | V |
AINM to GND | –0.3 | 0.3 | V |
Digital input voltage to GND | –0.3 | DVDD + 0.3 | V |
Storage temperature, Tstg | –60 | 150 | °C |
VALUE | UNIT | |||
---|---|---|---|---|
V(ESD) | Electrostatic discharge | Human-body model (HBM), per AEC Q100-002(1) | ±2000 | V |
Charged-device model (CDM), per AEC Q100-011 | ±1000 |
MIN | NOM | MAX | UNIT | ||
---|---|---|---|---|---|
AVDD | Analog supply voltage range | 2.35 | 3.6 | V | |
DVDD | Digital supply voltage range | 1.65 | 3.6 | V | |
TA | Operating free-air temperature | –40 | 125 | °C |
THERMAL METRIC(1) | ADS7049-Q1 | UNIT | |
---|---|---|---|
DCU (VSSOP) | |||
8 PINS | |||
RθJA | Junction-to-ambient thermal resistance | 181.8 | °C/W |
RθJC(top) | Junction-to-case (top) thermal resistance | 50.8 | °C/W |
RθJB | Junction-to-board thermal resistance | 73.9 | °C/W |
ψJT | Junction-to-top characterization parameter | 1.0 | °C/W |
ψJB | Junction-to-board characterization parameter | 73.9 | °C/W |
RθJC(bot) | Junction-to-case (bottom) thermal resistance | N/A | °C/W |
PARAMETER | TEST CONDITIONS | MIN | TYP | MAX | UNIT | ||
---|---|---|---|---|---|---|---|
ANALOG INPUT | |||||||
Full-scale input voltage span(1) | 0 | AVDD | V | ||||
Absolute input voltage range | AINP to GND | –0.1 | AVDD + 0.1 | V | |||
AINM to GND | –0.1 | 0.1 | |||||
CS | Sampling capacitance | 15 | pF | ||||
SYSTEM PERFORMANCE | |||||||
Resolution | 12 | Bits | |||||
NMC | No missing codes | 12 | Bits | ||||
INL | Integral nonlinearity | AVDD = 3 V | –1 | ±0.5 | 1 | LSB(2) | |
DNL | Differential nonlinearity | AVDD = 3 V | –0.99 | ±0.5 | 1 | LSB | |
EO | Offset error | Uncalibrated | ±12 | LSB | |||
Calibrated(6) | AVDD = 3 V | –3 | ±0.5 | 3 | |||
dVOS/dT | Offset error drift with temperature | ±5 | ppm/°C | ||||
EG | Gain error | AVDD = 3 V | –0.1 | ±0.05 | 0.1 | %FS | |
Gain error drift with temperature | No calibration | ±2 | ppm/°C | ||||
SAMPLING DYNAMICS | |||||||
tACQ | Acquisition time | 90 | ns | ||||
Maximum throughput rate | 32-MHz SCLK, AVDD = 2.35 V to 3.6 V | 2 | MHz | ||||
DYNAMIC CHARACTERISTICS | |||||||
SNR | Signal-to-noise ratio(4) | fIN = 2 kHz, AVDD = 3 V | 68 | 70 | dB | ||
THD | Total harmonic distortion(4)(3) | fIN = 2 kHz, AVDD = 3 V | –80 | dB | |||
SINAD | Signal-to-noise and distortion(4) | fIN = 2 kHz, AVDD = 3 V | 67.5 | 69.5 | dB | ||
SFDR | Spurious-free dynamic range(4) | fIN = 2 kHz, AVDD = 3 V | 80 | dB | |||
BW(fp) | Full-power bandwidth | At –3 dB, AVDD = 3 V | 25 | MHz | |||
DIGITAL INPUT/OUTPUT (CMOS Logic Family) | |||||||
VIH | High-level input voltage(5) | 0.65 × DVDD | DVDD + 0.3 | V | |||
VIL | Low-level input voltage(5) | –0.3 | 0.35 × DVDD | V | |||
VOH | High-level output voltage(5) | At Isource = 500 µA | 0.8 × DVDD | DVDD | V | ||
At Isource = 2 mA | DVDD – 0.45 | DVDD | |||||
VOL | Low-level output voltage(5) | At Isink = 500 µA | 0 | 0.2 × DVDD | V | ||
At Isink = 2 mA | 0 | 0.45 | |||||
POWER-SUPPLY REQUIREMENTS | |||||||
AVDD | Analog supply voltage | 2.35 | 3 | 3.6 | V | ||
DVDD | Digital I/O supply voltage | 1.65 | 3 | 3.6 | V | ||
IAVDD | Analog supply current | At 2 MSPS with AVDD = 3 V | 380 | 460 | µA | ||
IDVDD | Digital supply current | AVDD = 3 V, no load, no transitions | 10 | µA | |||
PD | Power dissipation | At 2 MSPS with AVDD = 3 V | 1.14 | 1.38 | mW |
MIN | TYP | MAX | UNIT | ||
---|---|---|---|---|---|
tACQ | Acquisition time | 90 | ns | ||
fSCLK | SCLK frequency | 0.016 | 32 | MHz | |
tSCLK | SCLK period | 31.25 | ns | ||
tPH_CK | SCLK high time | 0.45 | 0.55 | tSCLK | |
tPL_CK | SCLK low time | 0.45 | 0.55 | tSCLK | |
tPH_CS | CS high time | 30 | ns | ||
tSU_CSCK | Setup time: CS falling to SCLK falling | 12 | ns | ||
tD_CKCS | Delay time: last SCLK falling to CS rising | 10 | ns |
PARAMETER | TEST CONDITIONS | MIN | TYP | MAX | UNIT | |
---|---|---|---|---|---|---|
fTHROUGHPUT | Throughput | 2 | MSPS | |||
tCYCLE | Cycle time | 0.5 | µs | |||
tCONV | Conversion time | 12.5 × tSCLK + tSU_CSCK | ns | |||
tDV_CSDO | Delay time: CS falling to data enable | 10 | ns | |||
tD_CKDO | Delay time: SCLK falling to (next) data valid on DOUT | AVDD = 2.35 V to 3.6 V | 25 | ns | ||
tDZ_CSDO | Delay time: CS rising to DOUT going to tri-state | 5 | ns |
SNR = 70.29 dB, THD = –84.04 dB, fIN = 2 kHz, number of samples = 65536 |
fIN = 2 kHz |
fIN = 2 kHz |
fIN = 2 kHz |
fIN = 2 kHz |
AVDD = 3 V |
fSample = 2 MSPS |
fSample = 2 MSPS |
fIN = 2 kHz |
fIN = 2 kHz |
SNR = 69.92 dB, THD = –80.05 dB, fIN = 250 kHz, number of samples = 65536 |
fIN = 2 kHz |
fIN = 2 kHz |
Mean code = 2046.92, sigma = 0.42 |
AVDD = 3 V |
fIN = 2 kHz |
fIN = 2 kHz |
The device complies with the JESD8-7A standard for DVDD from 1.65 V to 1.95 V. Figure 32 shows voltage levels for the digital input and output pins.
The ADS7049-Q1 is an ultra-low-power, miniature analog-to-digital converter (ADC) that supports a wide analog input range. The analog input range for the device is defined by the AVDD supply voltage. The device samples the input voltage across the AINP and AINM pins on the CS falling edge and starts the conversion. The clock provided on the SCLK pin is used for conversion and data transfer. During conversions, both the AINP and AINM pins are disconnected from the sampling circuit. After the conversion completes, the sampling capacitors are reconnected across the AINP and AINM pins and the ADS7049-Q1 enters acquisition phase.
The device has an internal offset calibration. The offset calibration can be initiated by the user either on power-up or during normal operation; see the Offset Calibration section for more details.
The device also provides a simple serial interface to the host controller and operates over a wide range of digital power supplies. The ADS7049-Q1 requires only a 32-MHz SCLK for supporting a throughput of 2 MSPS. The digital interface also complies with the JESD8-7A (normal range) standard. The Functional Block Diagram section provides a block diagram of the device.
The device uses the analog supply voltage (AVDD) as a reference, as shown in Figure 33. The AVDD pin is recommended to be decoupled with a 3.3-µF, low equivalent series resistance (ESR) ceramic capacitor.. The AVDD pin functions as a switched capacitor load to the source powering AVDD. The decoupling capacitor provides the instantaneous charge required by the internal circuit and helps in maintaining a stable dc voltage on the AVDD pin. The AVDD pin is recommended to be powered with a low output impedance and low-noise regulator (such as the TPS73230).
The device supports single-ended analog inputs. The ADC samples the difference between AINP and AINM and converts for this voltage. The device is capable of accepting a signal from –100 mV to 100 mV on the AINM input and is useful in systems where the sensor or signal-conditioning block is far from the ADC. In such a scenario, there can be a difference between the ground potential of the sensor or signal conditioner and the ADC ground. In such cases, use separate wires to connect the ground of the sensor or signal conditioner to the AINM pin. The AINP input is capable of accepting signals from 0 V to AVDD. Figure 34 represents the equivalent analog input circuits for the sampling stage. The device has a low-pass filter followed by the sampling switch and sampling capacitor. The sampling switch is represented by an RS (typically 50 Ω) resistor in series with an ideal switch and CS (typically 15 pF) is the sampling capacitor. The ESD diodes are connected from both analog inputs to AVDD and ground.
The analog input full-scale range (FSR) is equal to the reference voltage of the ADC. The reference voltage for the device is equal to the analog supply voltage (AVDD). Thus, the device FSR can be determined by Equation 1:
The device output is in straight binary format. The device resolution for a single-ended input can be computed by Equation 2:
where
Figure 35 and Table 1 show the ideal transfer characteristics for the device.
INPUT VOLTAGE (AINP – AINM) | CODE | DESCRIPTION | IDEAL OUTPUT CODE |
---|---|---|---|
≤1 LSB | NFSC | Negative full-scale code | 000 |
1 LSB to 2 LSBs | NFSC + 1 | — | 001 |
(VREF / 2) to (VREF / 2) + 1 LSB | MC | Mid code | 800 |
(VREF / 2) + 1 LSB to (VREF / 2) + 2 LSBs | MC + 1 | — | 801 |
≥ VREF – 1 LSB | PFSC | Positive full-scale code | FFF |
The device supports a simple, SPI-compatible interface to the external host. The CS signal defines one conversion and serial transfer frame. A frame starts with a CS falling edge and ends with a CS rising edge. The SDO pin outputs the ADC conversion results. Figure 36 shows a detailed timing diagram for the serial interface. A minimum delay of tSU_CSCK must elapse between the CS falling edge and the first SCLK falling edge. The device uses the clock provided on the SCLK pin for conversion and data transfer. The conversion result is available on the SDO pin with the first two bits set to 0, followed by 12 bits of the conversion result. The first zero is launched on the SDO pin on the CS falling edge. Subsequent bits (starting with another 0 followed by the conversion result) are launched on the SDO pin on subsequent SCLK falling edges. The SDO output remains low after 14 SCLKs. A CS rising edge ends the frame and brings the serial data bus to tri-state. For acquisition of the next sample, a minimum time of tACQ must be provided after the conversion of the current sample is completed. For details on timing specifications, see the Timing Requirements table.
The device initiates an offset calibration on the first CS falling edge after power-up and the SDO output remains low during the first serial transfer frame after power-up. For further details, see the Offset Calibration section.
The ADS7049-Q1 includes a feature to calibrate the device internal offset. During offset calibration, the analog input pins (AINP and AINM) are disconnected from the sampling stage. The device includes an internal offset calibration register (OCR) that stores the offset calibration result. The OCR is an internal register and cannot be accessed by the user through the serial interface. The OCR is reset to zero on power-up. Therefore, it is recommended to calibrate the offset on power-up in order to bring the offset error within the specified limits. If the operating temperature or analog supply voltage reflect a significant change, the offset can be recalibrated during normal operation. Figure 37 shows the offset calibration process.
The device initiates offset calibration on the first CS falling edge after power-up and calibration completes if the CS pin remains low for at least 16 SCLK falling edges after the first CS falling edge. The SDO output remains low during calibration. The minimum acquisition time must be provided after calibration for acquiring the first sample. If the device is not provided with at least 16 SCLKs during the first serial transfer frame after power-up, the OCR is not updated. Table 2 provides the timing parameters for offset calibration on power-up.
For subsequent samples, the device adjusts the conversion results with the value stored in the OCR. The conversion result adjusted with the value stored in OCR is provided by the device on the SDO output. Figure 38 shows the timing diagram for offset calibration on power-up.
MIN | TYP | MAX | UNIT | ||
---|---|---|---|---|---|
fCLK-CAL | SCLK frequency for calibration | 16 | MHz | ||
tPOWERUP-CAL | Calibration time at power-up | 15 × tSCLK | ns | ||
tACQ | Acquisition time | 90 | ns | ||
tPH_CS | CS high time | tACQ | ns | ||
tSU_CSCK | Setup time: CS falling to SCLK falling | 12 | ns | ||
tD_CKCS | Delay time: last SCLK falling to CS rising | 10 | ns |
Offset calibration can be done during normal device operation if at least 32 SCLK falling edges are provided in one serial transfer frame. During the first 14 SCLKs, the device converts the sample acquired on the CS falling edge and provides data on the SDO output. The device initiates the offset calibration on the 17th SCLK falling edge and calibration completes on the 32nd SCLK falling edge. The SDO output remains low after the 14th SCLK falling edge and SDO goes to tri-state after CS goes high. If the device is provided with less than 32 SCLKs during a serial transfer frame, the OCR is not updated. Table 3 provides the timing parameters for offset calibration during normal operation.
For subsequent samples, the device adjusts the conversion results with the value stored in the OCR. The conversion result adjusted with the value stored in the OCR is provided by the device on the SDO output. Figure 39 shows the timing diagram for offset calibration during normal operation.
MIN | TYP | MAX | UNIT | ||
---|---|---|---|---|---|
fCLK-CAL | SCLK frequency for calibration | 16 | MHz | ||
tCAL | Calibration time during normal operation | 15 × tSCLK | ns | ||
tACQ | Acquisition time | 90 | ns | ||
tPH_CS | CS high time | tACQ | ns | ||
tSU_CSCK | Setup time: CS falling to SCLK falling | 12 | ns | ||
tD_CKCS | Delay time: last SCLK falling to CS rising | 10 | ns |
NOTE
Information in the following applications sections is not part of the TI component specification, and TI does not warrant its accuracy or completeness. TI’s customers are responsible for determining suitability of components for their purposes. Customers should validate and test their design implementation to confirm system functionality.
The two primary circuits required to maximize the performance of a SAR ADC are the input driver and the reference driver circuits. This section details some general principles for designing the input driver circuit, reference driver circuit, and provides some application circuits designed for the ADS7049-Q1.
The goal of this application is to design a single-supply digital acquisition (DAQ) circuit based on the ADS7049-Q1 with SNR greater than 70 dB and THD less than –80 dB for input frequencies of 2 kHz at a throughput of 2 MSPS.
The input driver circuit for a high-precision ADC mainly consists of two parts: a driving amplifier and a charge kickback filter. Careful design of the front-end circuit is critical to meet the linearity and noise performance of a high-precision ADC.
Figure 41 shows the input circuit of a typical SAR ADC. During the acquisition phase, the SW switch closes and connects the sampling capacitor (CSH) to the input driver circuit. This action introduces a transient on the input pins of the SAR ADC. An ideal amplifier with 0 Ω of output impedance and infinite current drive can settle this transient in zero time. For a real amplifier with non-zero output impedance and finite drive strength, this switched capacitor load can create stability issues.
For ac signals, the filter bandwidth must be kept low to band limit the noise fed into the ADC input, thereby increasing the SNR of the system. Besides filtering the noise from the front-end drive circuitry, the RC filter also helps attenuate the sampling charge injection from the switched-capacitor input stage of the ADC. A filter capacitor, CFLT, is connected across the ADC inputs. This capacitor helps reduce the sampling charge injection and provides a charge bucket to quickly charge the internal sample-and-hold capacitors during the acquisition process. As a rule of thumb, the value of this capacitor is at least 20 times the specified value of the ADC sampling capacitance. For this device, the input sampling capacitance is equal to 15 pF. Thus, the value of CFLT is greater than 300 pF. Select a COG- or NPO-type capacitor because these capacitor types have a high-Q, low-temperature coefficient, and stable electrical characteristics under varying voltages, frequency, and time.
Note that driving capacitive loads can degrade the phase margin of the input amplifiers, thus making the amplifier marginally unstable. To avoid amplifier stability issues, series isolation resistors (RFLT) are used at the output of the amplifiers. A higher value of RFLT is helpful from the amplifier stability perspective, but adds distortion as a result of interactions with the nonlinear input impedance of the ADC. Distortion increases with source impedance, input signal frequency, and input signal amplitude. Therefore, the selection of RFLT requires balancing the stability and distortion of the design.
The input amplifier bandwidth is typically much higher than the cutoff frequency of the antialiasing filter. Thus, a SPICE simulation is strongly recommended to be performed to confirm that the amplifier has more than 40° phase margin with the selected filter. Simulation is critical because even with high-bandwidth amplifiers, some amplifiers can require more bandwidth than others to drive similar filters.
To achieve a SINAD greater than 70 dB, the operational amplifier must have high bandwidth in order to settle the input signal within the acquisition time of the ADC. The operational amplifier must have low noise to keep the total system noise below 20% of the input-referred noise of the ADC. For the application circuit illustrated in Figure 40, the OPA365-Q1 is selected for its high bandwidth (50 MHz) and low noise (4.5 nV/√Hz).
For a step-by-step design procedure for a low-power, small form-factor digital acquisition (DAQ) circuit based on similar SAR ADCs, see the Three 12-Bit Data Acquisition Reference Designs Optimized for Low Power and Ultra-Small Form Factor TI Precision Design.
The analog supply voltage of the device is also used as a voltage reference for conversion. The AVDD pin is recommended to be decoupled with a 3.3-µF, low-ESR ceramic capacitor.
The ADS7049-Q1 has two separate power supplies: AVDD and DVDD. The device operates on AVDD; DVDD is used for the interface circuits. AVDD and DVDD can be independently set to any value within the permissible ranges. The AVDD supply also defines the full-scale input range of the device. Always set the AVDD supply to be greater than or equal to the maximum input signal to avoid saturation of codes. Decouple the AVDD and DVDD pins individually with 3.3-µF ceramic decoupling capacitors, as shown in Figure 43.
The current consumption from the DVDD supply depends on the DVDD voltage, load capacitance on the SDO line, and the output code. The load capacitance on the SDO line is charged by the current from the SDO pin on every rising edge of the data output and is discharged on every falling edge of the data output. The current consumed by the device from the DVDD supply can be calculated by Equation 3:
where
The number of transitions on the SDO output depends on the output code, and thus changes with the analog input. The maximum value of f occurs when data output on SDO change at every SCLK. SDO data changing at every SCLK results in an output code of AAAh or 555h. For an output code of AAAh or 555h at a 2-MSPS throughput, the frequency of transitions on the SDO output is 12 MHz.
For the current consumption to remain at the lowest possible value, keep the DVDD supply at the lowest permissible value and keep the capacitance on the SDO line as low as possible.
Figure 44 shows a board layout example for the ADS7049-Q1.
Some of the key considerations for an optimum layout with this device are:
Among ceramic surface-mount capacitors, COG (NPO) ceramic capacitors provide the best capacitance precision. The type of dielectric used in COG (NPO) ceramic capacitors provides the most stable electrical properties over voltage, frequency, and temperature changes.
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ESD 可能会损坏该集成电路。德州仪器 (TI) 建议通过适当的预防措施处理所有集成电路。如果不遵守正确的处理措施和安装程序 , 可能会损坏集成电路。
ESD 的损坏小至导致微小的性能降级 , 大至整个器件故障。 精密的集成电路可能更容易受到损坏 , 这是因为非常细微的参数更改都可能会导致器件与其发布的规格不相符。
SLYZ022 — TI Glossary.
This glossary lists and explains terms, acronyms, and definitions.