ZHCSFP4B November   2016  – June 2017 TMP468

PRODUCTION DATA.  

  1. 特性
  2. 应用
  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 Information
    5. 6.5 Electrical Characteristics
    6. 6.6 Two-Wire Timing Requirements
    7. 6.7 Typical Characteristics
  7. Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 Temperature Measurement Data
      2. 7.3.2 Series Resistance Cancellation
      3. 7.3.3 Differential Input Capacitance
      4. 7.3.4 Sensor Fault
      5. 7.3.5 THERM Functions
    4. 7.4 Device Functional Modes
      1. 7.4.1 Shutdown Mode (SD)
    5. 7.5 Programming
      1. 7.5.1 Serial Interface
        1. 7.5.1.1 Bus Overview
        2. 7.5.1.2 Bus Definitions
        3. 7.5.1.3 Serial Bus Address
        4. 7.5.1.4 Read and Write Operations
          1. 7.5.1.4.1 Single Register Reads
          2. 7.5.1.4.2 Block Register Reads
        5. 7.5.1.5 Timeout Function
        6. 7.5.1.6 High-Speed Mode
      2. 7.5.2 TMP468 Register Reset
      3. 7.5.3 Lock Register
    6. 7.6 Register Maps
      1. 7.6.1 Register Information
        1. 7.6.1.1  Pointer Register
        2. 7.6.1.2  Local and Remote Temperature Value Registers
        3. 7.6.1.3  Software Reset Register
        4. 7.6.1.4  THERM Status Register
        5. 7.6.1.5  THERM2 Status Register
        6. 7.6.1.6  Remote Channel Open Status Register
        7. 7.6.1.7  Configuration Register
        8. 7.6.1.8  η-Factor Correction Register
        9. 7.6.1.9  Remote Temperature Offset Register
        10. 7.6.1.10 THERM Hysteresis Register
        11. 7.6.1.11 Local and Remote THERM and THERM2 Limit Registers
        12. 7.6.1.12 Block Read - Auto Increment Pointer
        13. 7.6.1.13 Lock Register
        14. 7.6.1.14 Manufacturer and Device Identification Plus Revision Registers
  8. Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Application
      1. 8.2.1 Design Requirements
      2. 8.2.2 Detailed Design Procedure
      3. 8.2.3 Application Curve
  9. Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
  11. 11器件和文档支持
    1. 11.1 接收文档更新通知
    2. 11.2 社区资源
    3. 11.3 商标
    4. 11.4 静电放电警告
    5. 11.5 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

Detailed Description

Overview

The TMP468 device is a digital temperature sensor that combines a local temperature measurement channel and eight remote-junction temperature measurement channels in VQFN-16 or DSBGA-16 packages. The device has a two-wire-interface that is compatible with I2C or SMBus interfaces and includes four pin-programmable bus address options. The TMP468 is specified over a local device temperature range from –40°C to +125°C. The TMP468 device also contains multiple registers for programming and holding configuration settings, temperature limits, and temperature measurement results. The TMP468 pinout includes THERM and THERM2 outputs that signal overtemperature events based on the settings of temperature limit registers.

Functional Block Diagram

TMP468 FBD_01_SBOS762.gif

Feature Description

Temperature Measurement Data

The local and remote temperature sensors have a resolution of 13 bits (0.0625°C). Temperature data that result from conversions within the default measurement range are represented in binary form, as shown in the Standard Binary column of Table 1. Negative numbers are represented in two's-complement format. The resolution of the temperature registers extends to 255.9375°C and down to –256°C, but the actual device is limited to ranges as specified in the Electrical Characteristics table to meet the accuracy specifications. The TMP468 device is specified for ambient temperatures ranging from –40°C to +125°C; parameters in the Absolute Maximum Ratings table must be observed to prevent damage to the device.

Table 1. Temperature Data Format (Local and Remote Temperature)

TEMPERATURE
(°C)
LOCAL OR REMOTE TEMPERATURE REGISTER VALUE
(0.0625°C RESOLUTION)
STANDARD BINARY(1)
BINARY HEX
–64 1110 0000 0000 0000 E0 00
–50 1110 0111 0000 0000 E7 00
–25 1111 0011 1000 0000 F3 80
–0.1250 1111 1111 1111 0000 FF F0
–0.0625 1111 1111 1111 1000 FF F8
0 0000 0000 0000 0000 00 00
0.0625 0000 0000 0000 1000 00 08
0.1250 0000 0000 0001 0000 00 10
0.1875 0000 0000 0001 1000 00 18
0.2500 0000 0000 0010 0000 00 20
0.3125 0000 0000 0010 1000 00 28
0.3750 0000 0000 0011 0000 00 30
0.4375 0000 0000 0011 1000 00 38
0.5000 0000 0000 0100 0000 00 40
0.5625 0000 0000 0100 1000 00 48
0.6250 0000 0000 0101 0000 00 50
0.6875 0000 0000 0101 1000 00 58
0.7500 0000 0000 0110 0000 00 60
0.8125 0000 0000 0110 1000 00 68
0.8750 0000 0000 0111 0000 00 70
0.9375 0000 0000 0111 1000 00 78
1 0000 0000 1000 0000 00 80
5 0000 0010 1000 0000 02 80
10 0000 0101 0000 0000 05 00
25 0000 1100 1000 0000 0C 80
50 0001 1001 0000 0000 19 00
75 0010 0101 1000 0000 25 80
100 0011 0010 0000 0000 32 00
125 0011 1110 1000 0000 3E 80
127 0011 1111 1000 0000 3F 80
150 0100 1011 0000 0000 4B 00
175 0101 0111 1000 0000 57 80
191 0101 1111 1000 0000 5F 80
Resolution is 0.0625°C per count. Negative numbers are represented in two's-complement format.

Both local and remote temperature data use two bytes for data storage with a two's-complement format for negative numbers. The high byte stores the temperature with 2°C resolution. The second or low byte stores the decimal fraction value of the temperature and allows a higher measurement resolution, as shown in Table 1. The measurement resolution for both the local and the remote channels is 0.0625°C.

Series Resistance Cancellation

Series resistance cancellation automatically eliminates the temperature error caused by the resistance of the routing to the remote transistor or by the resistors of the optional external low-pass filter. A total up to 1-kΩ series resistance can be cancelled by the TMP468 device, which eliminates the need for additional characterization and temperature offset correction. See Figure 8 for details on the effects of series resistance on sensed remote temperature error.

Differential Input Capacitance

The TMP468 device tolerates differential input capacitance of up to 1000 pF with minimal change in temperature error. The effect of capacitance on the sensed remote temperature error is illustrated in Figure 9.

Sensor Fault

The TMP468 device can sense a fault at the D+ resulting from an incorrect diode connection. The TMP468 device can also sense an open circuit. Short-circuit conditions return a value of –256°C. The detection circuitry consists of a voltage comparator that trips when the voltage at D+ exceeds (V+) – 0.3 V (typical). The comparator output is continuously checked during a conversion. If a fault is detected, then the RxOP bit in the Remote Channel Status register is set to 1.

When not using the remote sensor with the TMP468 device, the corresponding D+ and D– inputs must be connected together to prevent meaningless fault warnings.

THERM Functions

Operation of the THERM (pin B3) and THERM2 (pin C3) interrupt pins are shown in Figure 14.

The hysteresis value is stored in the THERM Hysteresis register and applies to both the THERM and THERM2 interrupts.

TMP468 ai_thermresp_slos877.gif
Figure 14. THERM and THERM2 Interrupt Operation

Device Functional Modes

Shutdown Mode (SD)

The TMP468 shutdown mode enables the user to save maximum power by shutting down all device circuitry other than the serial interface, and reducing current consumption to typically less than 0.3 μA; see Figure 13. Shutdown mode is enabled when the shutdown bit (SD, bit 5) of the Configuration Register is HIGH; the device shuts down immediately once the current conversion is complete. When the SD bit is LOW, the device maintains a continuous-conversion state.

Programming

Serial Interface

The TMP468 device operates only as a slave device on the two-wire bus (I2C or SMBus). Connections to either bus are made using the open-drain I/O lines, SDA, and SCL. The SDA and SCL pins feature integrated spike suppression filters and Schmitt triggers to minimize the effects of input spikes and bus noise. The TMP468 device supports the transmission protocol for fast (1 kHz to 400 kHz) and high-speed (1 kHz to 2.56 MHz) modes. All data bytes are transmitted MSB first.

While the TMP468 device is unpowered bus traffic on SDA and SCL may continue without any adverse effects to the communication or to the TMP468 device itself. As the TMP468 device is powering up, the device does not load the bus, and as a result the bus traffic may continue undisturbed.

Bus Overview

The TMP468 device is compatible with the I2C or SMBus interface. In I2C or SMBus protocol, the device that initiates the transfer is called a master, and the devices controlled by the master are slaves. The bus must be controlled by a master device that generates the serial clock (SCL), controls the bus access, and generates the start and stop conditions.

To address a specific device, a start condition is initiated. A start condition is indicated by pulling the data line (SDA) from a high-to-low logic level when SCL is high. All slaves on the bus shift in the slave address byte, with the last bit indicating whether a read or write operation is intended. During the ninth clock pulse, the addressed slave responds to the master by generating an acknowledge (ACK) bit and pulling SDA low.

Data transfer is then initiated and sent over eight clock pulses followed by an acknowledge bit (ACK). During data transfer, SDA must remain stable when SCL is high. A change in SDA when SCL is high is interpreted as a control signal. The TMP468 device has a word register structure (16-bit wide), with data writes always requiring two bytes. Data transfer occurs during the ACK at the end of the second byte.

After all data are transferred, the master generates a stop condition. A stop condition is indicated by pulling SDA from low to high when SCL is high.

Bus Definitions

The TMP468 device has a two-wire interface that is compatible with the I2C or SMBus interface. Figure 15 through Figure 20 illustrate the timing for various operations on the TMP468 device. The bus definitions are as follows:

    Bus Idle: Both SDA and SCL lines remain high.
    Start Data Transfer: A change in the state of the SDA line (from high to low) when the SCL line is high defines a start condition. Each data transfer initiates with a start condition.
    Stop Data Transfer: A change in the state of the SDA line (from low to high) when the SCL line is high defines a stop condition. Each data transfer terminates with a repeated start or stop condition.
    Data Transfer: The number of data bytes transferred between a start and stop condition is not limited and is determined by the master device. The receiver acknowledges the data transfer.
    Acknowledge: Each receiving device, when addressed, is obliged to generate an acknowledge bit. A device that acknowledges must pull down the SDA line during the acknowledge clock pulse in such a way that the SDA line is stable low during the high period of the acknowledge clock pulse. Take setup and hold times into account. On a master receive, data transfer termination can be signaled by the master generating a not-acknowledge on the last byte that is transmitted by the slave.
TMP468 Tmng_PtSet.gif Figure 15. Two-Wire Timing Diagram for Write Pointer Byte
TMP468 Tmng_PtSt2ByWr_SBOS762.gif Figure 16. Two-Wire Timing Diagram for Write Pointer Byte and Value Word
TMP468 Tmng_PtSt1ByRd_SBOS762.gif
The master must leave SDA high to terminate a single-byte read operation.
Figure 17. Two-Wire Timing Diagram for Pointer Set Followed by a Repeat Start and Single-Byte Read Format
TMP468 Tmng_PtSt2ByRd_v2_SBOS762.gif Figure 18. Two-Wire Timing Diagram for Pointer Byte Set Followed by a Repeat Start and Word (Two-Byte) Read
TMP468 Tmng_PtSt4ByRd_SBOS762.gif Figure 19. Two-Wire Timing Diagram for Pointer Byte Set Followed by a Repeat Start and Multiple-Word (N-Word) Read
TMP468 Tmng_MultByRd.gif Figure 20. Two-Wire Timing Diagram for Multiple-Word (N-Word) Read Without a Pointer Byte Set

Serial Bus Address

To communicate with the TMP468 device, the master must first address slave devices using a slave address byte. The slave address byte consists of seven address bits and a direction bit indicating the intent of executing a read or write operation. The TMP468 device allows up to four devices to be addressed on a single bus. The assigned device address depends on the ADD pin connection as described in Table 2.

Table 2. TMP468 Slave Address Options

ADD PIN CONNECTION SLAVE ADDRESS
BINARY HEX
GND 1001000 48
V+ 1001001 49
SDA 1001010 4A
SCL 1001011 4B

Read and Write Operations

Accessing a particular register on the TMP468 device is accomplished by writing the appropriate value to the pointer register. The value for the pointer register is the first byte transferred after the slave address byte with the R/W bit low. Every write operation to the TMP468 device requires a value for the pointer register (see Figure 16).

The TMP468 registers can be accessed with block or single register reads. Block reads are only supported for pointer values 80h to 88h. Registers at 80h through 88h mirror the Remote and Local Temperature registers (00h to 08h). Pointer values 00h to 08h are for single register reads.

Single Register Reads

When reading from the TMP468 device, the last value stored in the pointer register by a write operation is used to determine which register is read by a read operation. To change which register is read for a read operation, a new value must be written to the pointer register. This transaction is accomplished by issuing a slave address byte with the R/W bit low, followed by the pointer register byte; no additional data are required. The master can then generate a start condition and send the slave address byte with the R/W bit high to initiate the read command; see Figure 17 through Figure 19 for details of this sequence.

If repeated reads from the same register are desired, continually sending the pointer register bytes is not necessary because the TMP468 device retains the pointer register value until the value is changed by the next write operation. The register bytes are sent by the MSB first, followed by the LSB. If only one byte is read (MSB), a consecutive read of TMP468 device results in the MSB being transmitted first. The LSB can only be accessed through two-byte reads.

The master terminates a read operation by issuing a not-acknowledge (NACK) command at the end of the last byte to be read or transmitting a stop condition. For a single-byte operation, the master must leave the SDA line high during the acknowledge time of the first byte that is read from the slave.

The TMP468 register structure has a word (two-byte) length, so every write transaction must have an even number of bytes (MSB and LSB) following the pointer register value (see Figure 16). Data transfers occur during the ACK at the end of the second byte or LSB. If the transaction does not finish, signaled by the ACK at the end of the second byte, then the data is ignored and not loaded into the TMP468 register. Read transactions do not have the same restrictions and may be terminated at the end of the last MSB.

Block Register Reads

The TMP468 supports block mode reads at address 80h through 88h for temperature results alone. Setting the pointer register to 80h signals to the TMP468 device that a block of more than two bytes must be transmitted before a stop is issued. In this mode, the TMP468 device auto increments the internal pointer. After the 18 bytes of temperature data are transmitted, the internal pointer resets to 80h. If the transmission is terminated before register 88h is read, the pointer increments so a consecutive read (without a pointer set) can access the next register.

Timeout Function

The TMP468 device resets the serial interface if either SCL or SDA are held low for 17.5 ms (typical) between a start and stop condition. If the TMP468 device is holding the bus low, the device releases the bus and waits for a start condition. To avoid activating the timeout function, maintain a communication speed of at least 1 kHz for the SCL operating frequency.

High-Speed Mode

For the two-wire bus to operate at frequencies above 1 MHz, the master device must issue a high-speed mode (HS-mode) master code (0000 1xxx) as the first byte after a start condition to switch the bus to high-speed operation. The TMP468 device does not acknowledge the master code byte, but switches the input filters on SDA and SCL and the output filter on SDA to operate in HS-mode, allowing transfers up to 2.56 MHz. After the HS-mode master code is issued, the master transmits a two-wire slave address to initiate a data transfer operation. The bus continues to operate in HS-mode until a stop condition occurs on the bus. Upon receiving the stop condition, the TMP468 device switches the input and output filters back to fast mode.

TMP468 Register Reset

The TMP468 registers can be software reset by setting bit 15 of the Software Reset register (20h) to 1. This software reset restores the power-on-reset state to all TMP468 registers and aborts any conversion in progress.

Lock Register

All of the configuration and limit registers may be locked for writes (making the registers write-protected), which decreases the chance of software runaway from issuing false changes to these registers. The Lock column in Table 3 identifies which registers may be locked. Lock mode does not effect read operations. To activate the lock mode, Lock Register C4h must be set to 0x5CA6. The lock only remains active while the TMP468 device is powered up. Because the TMP468 device does not contain nonvolatile memory, the settings of the configuration and limit registers are lost once a power cycle occurs regardless if the registers are locked or unlocked.

In lock mode, the TMP468 device ignores a write operation to configuration and limit registers except for Lock Register C4h. The TMP468 device does not acknowledge the data bytes during a write operation to a locked register. To unlock the TMP468 registers, write 0xEB19 to register C4h. The TMP468 device powers up in locked mode, so the registers must be unlocked before the registers accept writes of new data.

Register Maps

Table 3. TMP468 Register Map

PTR POR LOCK TMP468 FUNCTIONAL REGISTER - BIT DESCRIPTION REGISTER DESCRIPTION
(HEX) (HEX) (Y/N) 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
00 0000 N/A LT12 LT11 LT10 LT9 LT8 LT7 LT6 LT5 LT4 LT3 LT2 LT1 LT0 0(1) 0 0 Local Temperature
01 0000 N/A RT12 RT11 RT10 RT9 RT8 RT7 RT6 RT5 RT4 RT3 RT2 RT1 RT0 0 0 0 Remote Temperature 1
02 0000 N/A RT12 RT11 RT10 RT9 RT8 RT7 RT6 RT5 RT4 RT3 RT2 RT1 RT0 0 0 0 Remote Temperature 2
03 0000 N/A RT12 RT11 RT10 RT9 RT8 RT7 RT6 RT5 RT4 RT3 RT2 RT1 RT0 0 0 0 Remote Temperature 3
04 0000 N/A RT12 RT11 RT10 RT9 RT8 RT7 RT6 RT5 RT4 RT3 RT2 RT1 RT0 0 0 0 Remote Temperature 4
05 0000 N/A RT12 RT11 RT10 RT9 RT8 RT7 RT6 RT5 RT4 RT3 RT2 RT1 RT0 0 0 0 Remote Temperature 5
06 0000 N/A RT12 RT11 RT10 RT9 RT8 RT7 RT6 RT5 RT4 RT3 RT2 RT1 RT0 0 0 0 Remote Temperature 6
07 0000 N/A RT12 RT11 RT10 RT9 RT8 RT7 RT6 RT5 RT4 RT3 RT2 RT1 RT0 0 0 0 Remote Temperature 7
08 0000 N/A RT12 RT11 RT10 RT9 RT8 RT7 RT6 RT5 RT4 RT3 RT2 RT1 RT0 0 0 0 Remote Temperature 8
20 0000 N/A RST 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Software Reset Register
21 N/A N/A R8TH R7TH R6TH R5TH R4TH R3TH R2TH R1TH LTH 0 0 0 0 0 0 0 THERM Status
22 N/A N/A R8TH2 R7TH2 R6TH2 R5TH2 R4TH2 R3TH2 R2TH2 R1TH2 LTH2 0 0 0 0 0 0 0 THERM2 Status
23 N/A N/A R8OPN R7OPN R6OPN R5OPN R4OPN R3OPN R2OPN R1OPN 0 0 0 0 0 0 0 0 Remote Channel OPEN Status
30 0F9C Y REN8 REN7 REN6 REN5 REN4 REN3 REN2 REN1 LEN OS SD CR2 CR1 CR0 BUSY 0 Configuration Register (Enables, OneShot, ShutDown, ConvRate, BUSY)
38 0080 Y 0 HYS11 HYS10 HYS9 HYS8 HYS7 HYS6 HYS5 HYS4 0 0 0 0 0 0 0 THERM Hysteresis
39 7FC0 Y LTH1_12 LTH1_11 LTH1_10 LTH1_09 LTH1_08 LTH1_07 LTH1_06 LTH1_05 LTH1_04 LTH1_03 0 0 0 0 0 0 Local Temperature THERM Limit
3A 7FC0 Y LTH2_12 LTH2_11 LTH2_10 LTH2_09 LTH2_08 LTH2_07 LTH2_06 LTH2_05 LTH2_04 LTH2_03 0 0 0 0 0 0 Local Temperature THERM2 Limit
40 0000 Y ROS12 ROS12(2) ROS10 ROS9 ROS8 ROS7 ROS6 ROS5 ROS4 ROS3 ROS2 ROS1 ROS0 0 0 0 Remote Temperature 1 Offset
41 0000 Y RNC7 RNC6 RNC5 RNC4 RNC3 RNC2 RNC1 RNC0 0 0 0 0 0 0 0 0 Remote Temperature 1 η-Factor Correction
42 7FC0 Y RTH1_12 RTH1_11 RTH1_10 RTH1_09 RTH1_08 RTH1_07 RTH1_06 RTH1_05 RTH1_04 RTH1_03 0 0 0 0 0 0 Remote Temperature 1 THERM Limit
43 7FC0 Y RTH2_12 RTH2_11 RTH2_10 RTH2_09 RTH2_08 RTH2_07 RTH2_06 RTH2_05 RTH2_04 RTH2_03 0 0 0 0 0 0 Remote Temperature 1 THERM2 Limit
48 0000 Y ROS12 ROS12 ROS10 ROS9 ROS8 ROS7 ROS6 ROS5 ROS4 ROS3 ROS2 ROS1 ROS0 0 0 0 Remote Temperature 2 Offset
49 0000 Y RNC7 RNC6 RNC5 RNC4 RNC3 RNC2 RNC1 RNC0 0 0 0 0 0 0 0 0 Remote Temperature 2 η-Factor Correction
4A 7FC0 Y RTH1_12 RTH1_11 RTH1_10 RTH1_09 RTH1_08 RTH1_07 RTH1_06 RTH1_05 RTH1_04 RTH1_03 0 0 0 0 0 0 Remote Temperature 2 THERM Limit
4B 7FC0 Y RTH2_12 RTH2_11 RTH2_10 RTH2_09 RTH2_08 RTH2_07 RTH2_06 RTH2_05 RTH2_04 RTH2_03 0 0 0 0 0 0 Remote Temperature 2 THERM2 Limit
50 0000 Y ROS12 ROS12 ROS10 ROS9 ROS8 ROS7 ROS6 ROS5 ROS4 ROS3 ROS2 ROS1 ROS0 0 0 0 Remote Temperature 3 Offset
51 0000 Y RNC7 RNC6 RNC5 RNC4 RNC3 RNC2 RNC1 RNC0 0 0 0 0 0 0 0 0 Remote Temperature 3 η-Factor Correction
52 7FC0 Y RTH1_12 RTH1_11 RTH1_10 RTH1_09 RTH1_08 RTH1_07 RTH1_06 RTH1_05 RTH1_04 RTH1_03 0 0 0 0 0 0 Remote Temperature 3 THERM Limit
53 7FC0 Y RTH2_12 RTH2_11 RTH2_10 RTH2_09 RTH2_08 RTH2_07 RTH2_06 RTH2_05 RTH2_04 RTH2_03 0 0 0 0 0 0 Remote Temperature 3 THERM2 limit
58 0000 Y ROS12 ROS12 ROS10 ROS9 ROS8 ROS7 ROS6 ROS5 ROS4 ROS3 ROS2 ROS1 ROS0 0 0 0 Remote temperature 4 Offset
59 0000 Y RNC7 RNC6 RNC5 RNC4 RNC3 RNC2 RNC1 RNC0 0 0 0 0 0 0 0 0 Remote Temperature 4 η-Factor Correction
5A 7FC0 Y RTH1_12 RTH1_11 RTH1_10 RTH1_09 RTH1_08 RTH1_07 RTH1_06 RTH1_05 RTH1_04 RTH1_03 0 0 0 0 0 0 Remote Temperature 4 THERM Limit
5B 7FC0 Y RTH2_12 RTH2_11 RTH2_10 RTH2_09 RTH2_08 RTH2_07 RTH2_06 RTH2_05 RTH2_04 RTH2_03 0 0 0 0 0 0 Remote Temperature 4 THERM2 Limit
60 0000 Y ROS12 ROS12 ROS10 ROS9 ROS8 ROS7 ROS6 ROS5 ROS4 ROS3 ROS2 ROS1 ROS0 0 0 0 Remote Temperature 5 Offset
61 0000 Y RNC7 RNC6 RNC5 RNC4 RNC3 RNC2 RNC1 RNC0 0 0 0 0 0 0 0 0 Remote Temperature 5 η-Factor Correction
62 7FC0 Y RTH1_12 RTH1_11 RTH1_10 RTH1_09 RTH1_08 RTH1_07 RTH1_06 RTH1_05 RTH1_04 RTH1_03 0 0 0 0 0 0 Remote Temperature 5 THERM Limit
63 7FC0 Y RTH2_12 RTH2_11 RTH2_10 RTH2_09 RTH2_08 RTH2_07 RTH2_06 RTH2_05 RTH2_04 RTH2_03 0 0 0 0 0 0 Remote Temperature 5 THERM2 Limit
68 0000 Y ROS12 ROS12 ROS10 ROS9 ROS8 ROS7 ROS6 ROS5 ROS4 ROS3 ROS2 ROS1 ROS0 0 0 0 Remote Temperature 6 Offset
69 0000 Y RNC7 RNC6 RNC5 RNC4 RNC3 RNC2 RNC1 RNC0 0 0 0 0 0 0 0 0 Remote Temperature 6 η-Factor Correction
6A 7FC0 Y RTH1_12 RTH1_11 RTH1_10 RTH1_09 RTH1_08 RTH1_07 RTH1_06 RTH1_05 RTH1_04 RTH1_03 0 0 0 0 0 0 Remote Temperature 6 THERM Limit
6B 7FC0 Y RTH2_12 RTH2_11 RTH2_10 RTH2_09 RTH2_08 RTH2_07 RTH2_06 RTH2_05 RTH2_04 RTH2_03 0 0 0 0 0 0 Remote Temperature 6 THERM2 Limit
70 0000 Y ROS12 ROS12 ROS10 ROS9 ROS8 ROS7 ROS6 ROS5 ROS4 ROS3 ROS2 ROS1 ROS0 0 0 0 Remote Temperature 7 Offset
71 0000 Y RNC7 RNC6 RNC5 RNC4 RNC3 RNC2 RNC1 RNC0 0 0 0 0 0 0 0 0 Remote Temperature 7 η-Factor Correction
72 7FC0 Y RTH1_12 RTH1_11 RTH1_10 RTH1_09 RTH1_08 RTH1_07 RTH1_06 RTH1_05 RTH1_04 RTH1_03 0 0 0 0 0 0 Remote Temperature 7 THERM Limit
73 7FC0 Y RTH2_12 RTH2_11 RTH2_10 RTH2_09 RTH2_08 RTH2_07 RTH2_06 RTH2_05 RTH2_04 RTH2_03 0 0 0 0 0 0 Remote Temperature 7 THERM2 Limit
78 0000 Y ROS12 ROS12 ROS10 ROS9 ROS8 ROS7 ROS6 ROS5 ROS4 ROS3 ROS2 ROS1 ROS0 0 0 0 Remote Temperature 8 Offset
79 0000 Y RNC7 RNC6 RNC5 RNC4 RNC3 RNC2 RNC1 RNC0 0 0 0 0 0 0 0 0 Remote Temperature 8 η-Factor Correction
7A 7FC0 Y RTH1_12 RTH1_11 RTH1_10 RTH1_09 RTH1_08 RTH1_07 RTH1_06 RTH1_05 RTH1_04 RTH1_03 0 0 0 0 0 0 Remote Temperature 8 THERM Limit
7B 7FC0 Y RTH2_12 RTH2_11 RTH2_10 RTH2_09 RTH2_08 RTH2_07 RTH2_06 RTH2_05 RTH2_04 RTH2_03 0 0 0 0 0 0 Remote Temperature 8 THERM2 Limit
80 0000 N/A LT12 LT11 LT10 LT9 LT8 LT7 LT6 LT5 LT4 LT3 LT2 LT1 LT0 0 0 0 Local Temperature (Block Read Range - Auto Increment Pointer Register)
81 0000 N/A RT12 RT11 RT10 RT9 RT8 RT7 RT6 RT5 RT4 RT3 RT2 RT1 RT0 0 0 0 Remote Temperature 1 (Block Read Range - Auto Increment Pointer Register)
82 0000 N/A RT12 RT11 RT10 RT9 RT8 RT7 RT6 RT5 RT4 RT3 RT2 RT1 RT0 0 0 0 Remote Temperature 2 (Block Read Range - Auto Increment Pointer Register)
83 0000 N/A RT12 RT11 RT10 RT9 RT8 RT7 RT6 RT5 RT4 RT3 RT2 RT1 RT0 0 0 0 Remote Temperature 3 (Block Read Range - Auto Increment Pointer Register)
84 0000 N/A RT12 RT11 RT10 RT9 RT8 RT7 RT6 RT5 RT4 RT3 RT2 RT1 RT0 0 0 0 Remote Temperature 4 (Block Read Range - Auto Increment Pointer Register)
85 0000 N/A RT12 RT11 RT10 RT9 RT8 RT7 RT6 RT5 RT4 RT3 RT2 RT1 RT0 0 0 0 Remote Temperature 5 (Block Read Range - Auto Increment Pointer Register)
86 0000 N/A RT12 RT11 RT10 RT9 RT8 RT7 RT6 RT5 RT4 RT3 RT2 RT1 RT0 0 0 0 Remote Temperature 6 (Block Read Range - Auto Increment Pointer Register)
87 0000 N/A RT12 RT11 RT10 RT9 RT8 RT7 RT6 RT5 RT4 RT3 RT2 RT1 RT0 0 0 0 Remote Temperature 7 (Block Read Range - Auto Increment Pointer Register)
88 0000 N/A RT12 RT11 RT10 RT9 RT8 RT7 RT6 RT5 RT4 RT3 RT2 RT1 RT0 0 0 0 Remote Temperature 8 (Block Read Range - Auto Increment Pointer Register)
C4 8000 N/A Write 0x5CA6 to lock registers and 0xEB19 to unlock registers Lock Register. This locks the registers after initialization.
Read back: locked 0x8000; unlocked 0x0000
FE 5449 N/A 0 1 0 1 0 1 0 0 0 1 0 0 1 0 0 1 Manufacturers Identification Register
FF 0468 N/A 0 0 0 0 0 1 0 0 0 1 1 0 1 0 0 0 Device Identification/Revision Register
Register bits highlighted in purple are reserved for future use and always report 0; writes to these bits are ignored.
Register bits highlighted in green show sign extended values.

Register Information

The TMP468 device contains multiple registers for holding configuration information, temperature measurement results, and status information. These registers are described in Figure 21 and Table 3.

Pointer Register

shows the internal register structure of the TMP468 device. The 8-bit pointer register addresses a given data register. The pointer register identifies which of the data registers must respond to a read or write command on the two-wire bus. This register is set with every write command. A write command must be issued to set the proper value in the pointer register before executing a read command. Table 3 describes the pointer register and the internal structure of the TMP468 registers. The power-on-reset (POR) value of the pointer register is 00h (0000 0000b). Table 3 lists a summary of the pointer values for the different registers. Writing data to unassigned pointer values are ignored and does not affect the operation of the device. Reading an unassigned register returns undefined data and is ACKed.

TMP468 Reg_Strct_01_v3_SB0S762.gif Figure 21. TMP468 Internal Register Structure

Local and Remote Temperature Value Registers

The TMP468 device has multiple 16-bit registers that hold 13-bit temperature measurement results. The 13 bits of the local temperature sensor result are stored in register 00h. The 13 bits of the eight remote temperature sensor results are stored in registers 01h through 08h. The four assigned LSBs of both the local (LT3:LT0) and remote (RT3:RT0) sensors indicate the temperature value after the decimal point (for example, if the temperature result is 10.0625°C, then the high byte is 0000 0101 and the low byte is 0000 1000). These registers are read-only and are updated by the ADC each time a temperature measurement is complete. Asynchronous reads are supported, so a read operation can occur at any time and results in valid conversion results being transmitted once the first conversion is complete after power up for the channel being accessed. If after power up a read is initiated before a conversion is complete, the read operation results in all zeros (0x0000).

Software Reset Register

The Software Reset Register allows the user to reset the TMP468 registers through software by setting the reset bit (RST, bit 15) to 1. The power-on-reset value for this register is 0x0000. Resets are ignored when the device is in lock mode, so writing a 1 to the RST bit does not reset any registers.

Table 4. Software Reset Register Format

STATUS REGISTER (READ = 20h, WRITE = 20h, POR = 0x0000)
BIT NUMBER BIT NAME FUNCTION
15 RST 1 software reset device; writing a value of 0 is ignored
14-0 0 Reserved for future use; always reports 0

THERM Status Register

The THERM Status register reports the state of the THERM limit comparators for local and eight remote temperatures. Table 5 lists the status register bits. The THERM Status register is read-only and is read by accessing pointer address 21h.

Table 5. THERM Status Register Format

THERM STATUS REGISTER (READ = 21h, WRITE = N/A)
BIT NUMBER BIT NAME FUNCTION
15 R8TH 1 when Remote 8 exceeds the THERM limit
14 R7TH 1 when Remote 7 exceeds the THERM limit
13 R6TH 1 when Remote 6 exceeds the THERM limit
12 R5TH 1 when Remote 5 exceeds the THERM limit
11 R4TH 1 when Remote 4 exceeds the THERM limit
10 R3TH 1 when Remote 3 exceeds the THERM limit
9 R2TH 1 when Remote 2 exceeds the THERM limit
8 R1TH 1 when Remote 1 exceeds the THERM limit
7 LTH 1 when Local sensor exceeds the THERM limit
6:0 0 Reserved for future use; always reports 0.

The R8TH:R1TH and LTH flags are set when the corresponding temperature exceeds the respective programmed THERM limit (39h, 42h, 4Ah, 52h, 5Ah, 62h, 6Ah, 72h, 7Ah). These flags are reset automatically when the temperature returns below the THERM limit minus the value set in the THERM Hysteresis register (38h). The THERM output goes low in the case of overtemperature on either the local or remote channels, and goes high as soon as the measurements are less than the THERM limit minus the value set in the THERM Hysteresis register. The THERM Hysteresis register (38h) allows hysteresis to be added so that the flag resets and the output goes high when the temperature returns to or goes below the limit value minus the hysteresis value.

THERM2 Status Register

The THERM2 Status register reports the state of the THERM2 limit comparators for local and remote 1-8 temperatures. Table 6 lists the status register bits. The THERM2 Status register is read-only and is read by accessing pointer address 22h.

Table 6. THERM2 Status Register Format

THERM2 STATUS REGISTER (READ = 22h, WRITE = N/A)
BIT NUMBER BIT NAME FUNCTION
15 R8TH2 1 when Remote 8 exceeds the THERM2 limit
14 R7TH2 1 when Remote 7 exceeds the THERM2 limit
13 R6TH2 1 when Remote 6 exceeds the THERM2 limit
12 R5TH2 1 when Remote 5 exceeds the THERM2 limit
11 R4TH2 1 when Remote 4 exceeds the THERM2 limit
10 R3TH2 1 when Remote 3 exceeds the THERM2 limit
9 R2TH2 1 when Remote 2 exceeds the THERM2 limit
8 R1TH2 1 when Remote 1 exceeds the THERM2 limit
7 LTH2 1 when Local Sensor exceeds the THERM2 limit
6:0 0 Reserved for future use; always reports 0.

The R8TH2:R1TH2 and LTH2 flags are set when the corresponding temperature exceeds the respective programmed THERM2 limit (3Ah, 43h, 4Bh, 53h, 5Bh, 63h, 6Bh, 73h, 7Bh). These flags are reset automatically when the temperature returns below the THERM2 limit minus the value set in the THERM Hysteresis register (38h). The THERM2 output goes low in the case of overtemperature on either the local or remote channels, and goes high as soon as the measurements are less than the THERM2 limit minus the value set in the THERM Hysteresis register. The THERM Hysteresis register (38h) allows hysteresis to be added so that the flag resets and the output goes high when the temperature returns to or goes below the limit value minus the hysteresis value.

Remote Channel Open Status Register

The Remote Channel Open Status register reports the state of the connection of remote channels one through eight. Table 7 lists the status register bits. The Remote Channel Open Status register is read-only and is read by accessing pointer address 23h.

Table 7. Remote Channel Open Status Register Format

REMOTE CHANNEL OPEN STATUS REGISTER (READ = 23h, WRITE = N/A)
BIT NUMBER BIT NAME FUNCTION
15 R8OPEN 1 when Remote 8 channel is an open circuit
14 R7OPEN 1 when Remote 7 channel is an open circuit
13 R6OPEN 1 when Remote 6 channel is an open circuit
12 R5OPEN 1 when Remote 5 channel is an open circuit
11 R4OPEN 1 when Remote 4 channel is an open circuit
10 R3OPEN 1 when Remote 3 channel is an open circuit
9 R2OPEN 1 when Remote 2 channel is an open circuit
8 R1OPEN 1 when Remote 1 channel is an open circuit
7:0 0 Reserved for future use; always reports 0.

The R8OPEN:R1OPEN bits indicate an open-circuit condition on remote sensors eight through one, respectively. The setting of these flags does not directly affect the state of the THERM or THERM2 output pins. Indirectly, the temperature reading(s) may be erroneous and exceed the respective THERM and THERM2 limits, activating the THERM or THERM2 output pins.

Configuration Register

The Configuration Register sets the conversion rate, starts one-shot conversion of all enabled channels, enables conversion the temperature channels, controls the shutdown mode and reports when a conversion is in process. The Configuration Register is set by writing to pointer address 30h, and is read from pointer address 30h. Table 8 summarizes the bits of the Configuration Register.

Table 8. Configuration Register Bit Descriptions

CONFIGURATION REGISTER (READ = 30h, WRITE = 30h, POR = 0x0F9C)
BIT NUMBER NAME FUNCTION POWER-ON-RESET VALUE
15:8 REN8:REN1 1 = enable respective remote channel 8 through 1 conversions 1111 1111
7 LEN 1 = enable local channel conversion 1
6 OS 1 = start one-shot conversion on enabled channels 0
5 SD 1 = enables device shutdown 0
4:2 CR2:CR0 Conversion rate control bits; control conversion rates for all enabled channels from 16 seconds to continuous conversion 111
1 BUSY 1 when the ADC is converting (read-only bit ignores writes) 0
0 Reserved 0

The Remote Enable eight through one (REN8:REN1, bits 15:8) bits enable conversions on the respective remote channels. The Local Enable (LEN, bit 7) bit enables conversions of the local temperature channel. If all LEN and REN are set to 1 (default), this enables the ADC to convert the local and all remote temperatures. If the LEN is set to 0, the local temperature conversion is skipped. Similarly if a REN is set to 0, that remote temperature conversion channel is skipped. The TMP468 device steps through each enabled channel in a round-robin fashion in the following order: LOC, REM1, REM2, REM8, LOC, REM1, and so on. All local and remote temperatures are converted by the internal ADC by default after power up. The configuration register LEN and REN bits can be configured to save power by reducing the total ADC conversion time for applications that do not require all of the eight remote and local temperature information. Note writing all zeros to REN8:REN1 and LEN has the same effect as SD = 1 and OS = 0.

The shutdown bit (SD, bit 5) enables or disables the temperature-measurement circuitry. If SD = 0 (default), the TMP468 device converts continuously at the rate set in the conversion rate register. When SD is set to 1, the TMP468 device immediately stops the conversion in progress and instantly enters shutdown mode. When SD is set to 0 again, the TMP468 device resumes continuous conversions starting with the local temperature.

The BUSY bit = 1 if the ADC is making a conversion. This bit is set to 0 if the ADC is not converting.

After the TMP468 device is in shutdown mode, writing a 1 to the one-shot (OS, bit 6) bit starts a single ADC conversion of all the enabled temperature channels. This write operation starts one conversion and comparison cycle on either the eight remote and one local sensor or any combination of sensors, depending on the LEN and REN values in the Configuration Register (read address 30h). The TMP468 device returns to shutdown mode when the cycle is complete. Table 9 details the interaction of the SD, OS, LEN, and REN bits.

Table 9. Conversion Modes

WRITE READ FUNCTION
REN[8:1], LEN OS SD REN[8:1], LEN OS SD
All 0 All 0 0 1 Shutdown
At least 1 enabled 0 Written value 0 0 Continuous conversion
At least 1 enabled 0 1 Written value 0 1 Shutdown
At least 1 enabled 1 1 Written value 1 1 One-shot conversion

The conversion rate bits control the rate that the conversions occur (CR2:CR0, bits 4:2). The value of CR2:CR0 bits controls the idle time between conversions but not the conversion time itself, which allows the TMP468 device power dissipation to be balanced with the update rate of the temperature register. Table 10 describes the mapping for CR2:CR0 to the conversion rate or temperature register update rate.

Table 10. Conversion Rate

CR2:CR0 DECIMAL VALUE FREQUENCY (Hz) TIME (s)
000 0 0.0625 16
001 1 0.125 8
010 2 0.25 4
011 3 0.5 2
100 4 1 1
101 5 2 0.5
110 6 4 0.25
111 7 Continuous conversion; depends on number of enabled channels; see Table 11 (default).

Table 11. Continuous Conversion Times

NUMBER OF REMOTE CHANNELS ENABLED CONVERSION TIME (ms)
LOCAL DISABLED LOCAL ENABLED
0 0 15.5
1 15.8 31.3
2 31.6 47.1
3 47.4 62.9
4 63.2 78.7
5 79 94.5
6 94.8 110.3
7 110.6 126.1
8 126.4 141.9

The remaining bits of the configuration register are reserved and must always be set to 0. The POR value for this register is 0x0F9C.

η-Factor Correction Register

The TMP468 device allows for a different η-factor value to be used for converting remote channel measurements to temperature for each temperature channel. There are eight η-Factor Correction registers assigned: one to each of the remote input channels (addresses 41h, 49h, 51h, 59h, 61h, 69h, 71h and 79h). Each remote channel uses sequential current excitation to extract a differential VBE voltage measurement to determine the temperature of the remote transistor. Equation 1 shows this voltage and temperature.

Equation 1. TMP468 q_vbe_bos762.gif

The value η in Equation 1 is a characteristic of the particular transistor used for the remote channel. The POR value for the TMP468 device is η = 1.008. The value in the η-Factor Correction register can be used to adjust the effective η-factor, according to Equation 2 and Equation 3.

Equation 2. TMP468 q_neff_bos686.gif
Equation 3. TMP468 q_nadjust_bos686.gif

The η-factor correction value must be stored in a two's-complement format, which yields an effective data range from –128 to +127. The POR value for each register is 0000h, which does not affect register values unless a different value is written to the register. The resolution of the η-factor register changes linearly as the code changes and has a range from 0.0004292 to 0.0005476, with an average of 0.0004848.

Table 12. η-Factor Range

NADJUST ONLY BITS 15 TO 8 IN THE REGISTER ARE SHOWN η
BINARY HEX DECIMAL
0111 1111 7F 127 0.950205
0000 1010 0A 10 1.003195
0000 1000 08 8 1.004153
0000 0110 06 6 1.005112
0000 0100 04 4 1.006073
0000 0010 02 2 1.007035
0000 0001 01 1 1.007517
0000 0000 00 0 1.008
1111 1111 FF –1 1.008483
1111 1110 FE –2 1.008966
1111 1100 FC –4 1.009935
1111 1010 FA –6 1.010905
1111 1000 F8 –8 1.011877
1111 0110 F6 –10 1.012851
1000 0000 80 –128 1.073829

Remote Temperature Offset Register

The offset registers allow the TMP468 device to store any system offset compensation value that may result from precision calibration. The value in these registers is added to the remote temperature results upon every conversion. Each of the eight temperature channels have an independent assigned offset register (addresses 40h, 48h, 50h, 58h, 60h, 68h, 70h, and 78h). Combined with the independent η-factor corrections, this function allows for very accurate system calibration over the entire temperature range for each remote channel. The format of these registers is the same as the temperature value registers with a range from +127.9375 to –128. Take care to program this register with sign extension, as values above +127.9375 and below –128 are not supported.

THERM Hysteresis Register

The THERM Hysteresis register (address 38h) sets the value of the hysteresis used by the temperature comparison logic. All temperature reading comparisons have a common hysteresis. Hysteresis prevents oscillations from occurring on the THERM and THERM2 outputs as the measured temperature approaches the comparator threshold (see the THERM Functions section). The resolution of the THERM Hysteresis register is 1°C and ranges from 0°C to 255°C.

Local and Remote THERM and THERM2 Limit Registers

Each of the eight remote and the local temperature channels has associated independent THERM and THERM2 Limit registers. There are nine THERM registers (addresses 39h, 42h, 4Ah, 52h, 5Ah, 62h, 6Ah, 72h, and 7Ah) and nine THERM2 registers (addresses 39h, 43h, 4Bh, 53h, 5Bh, 63h, 6Bh, 73h, and 7Bh), 18 registers in total. The resolution of these registers is 0.5°C and ranges from +255.5°C to –255°C. See the THERM Functions section for more information.

Setting a THERM limit to 255.5°C disables the THERM limit comparison for that particular channel and disables the limit flag from being set in the THERM Status register. This prevents the associated channel from activating the THERM output. THERM2 limits, status, and outputs function similarly.

Block Read - Auto Increment Pointer

Block reads can be initiated by setting the pointer register to 80h to 87h. The temperature results are mirrored at pointer addresses 80h to 88h; temperature results for all the channels can be read with one read transaction. Setting the pointer register to any address from 80h to 88h signals to the TMP468 device that a block of more than two bytes must be transmitted before a design stop is issued. In block read mode, the TMP468 device auto increments the pointer address. After 88h, the pointer resets to 80h. The master must NACK the last byte read so the TMP468 device can discontinue driving the bus, which allows the master to initiate a stop. In this mode, the pointer continuously loops in the address range from 80h to 88h, so the register may be easily read multiple times. Block read does not disrupt the conversion process.

Lock Register

Register C4h allows the device configuration and limit registers to lock, as shown by the Lock column in Table 3. To lock the registers, write 0x5CA6. To unlock the registers, write 0xEB19. When the lock function is enabled, reading the register yields 0x8000; when unlocked, 0x0000 is transmitted.

Manufacturer and Device Identification Plus Revision Registers

The TMP468 device allows the two-wire bus controller to query the device for manufacturer and device identifications (IDs) to enable software identification of the device at the particular two-wire bus address. The manufacturer ID is obtained by reading from pointer address FEh; the device ID is obtained from register FFh. Note that the most significant byte of the Device ID register identifies the TMP468 device revision level. The TMP468 device reads 0x5449 for the manufacturer code and 0x0468 for the device ID code for the first release.