SBOS876B September   2017  – February 2020 TMP461-SP

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
    1.     Simplified Block Diagram
  3. 3 Description
  4. 4 Revision History
  5. 5 Pin Configuration and Functions
    1.     Pin Functions
  6. 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. 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
        1. 7.3.1.1 Standard Binary to Decimal Temperature Data Calculation Example
        2. 7.3.1.2 Standard Decimal to Binary Temperature Data Calculation Example
      2. 7.3.2 Series Resistance Cancellation
      3. 7.3.3 Differential Input Capacitance
      4. 7.3.4 Filtering
      5. 7.3.5 Sensor Fault
      6. 7.3.6 ALERT and 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
        5. 7.5.1.5 Timeout Function
        6. 7.5.1.6 High-Speed Mode
      2. 7.5.2 General-Call Reset
    6. 7.6 Register Map
      1. 7.6.1 Register Information
        1. 7.6.1.1  Pointer Register
        2. 7.6.1.2  Local and Remote Temperature Registers
        3. 7.6.1.3  Status Register
        4. 7.6.1.4  Configuration Register
        5. 7.6.1.5  Conversion Rate Register
        6. 7.6.1.6  One-Shot Start Register
        7. 7.6.1.7  Channel Enable Register
        8. 7.6.1.8  Consecutive ALERT Register
        9. 7.6.1.9  η-Factor Correction Register
        10. 7.6.1.10 Remote Temperature Offset Register
        11. 7.6.1.11 Manufacturer Identification Register
  8. 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
    3. 8.3 Radiation Environments
      1. 8.3.1 Single Event Latch-Up
      2. 8.3.2 Single Event Functional Interrupt
      3. 8.3.3 Single Event Upset
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Receiving Notification of Documentation Updates
    2. 11.2 Community Resources
    3. 11.3 Trademarks
    4. 11.4 Electrostatic Discharge Caution
    5. 11.5 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

7.3.4 Filtering

Remote junction temperature sensors are usually implemented in a noisy environment. Noise is most often created by fast digital signals that can corrupt measurements. The TMP461-SP device has a built-in, 65-kHz filter on the D+ and D– inputs to minimize the effects of noise. However, a bypass capacitor placed differentially across the inputs of the remote temperature sensor is recommended to make the application more robust against unwanted coupled signals. For this capacitor, select a value between 100 pF differential and 1 nF. Some applications attain better overall accuracy with additional series resistance. However, this increased accuracy is application-specific. When series resistance is added, the total value must not be greater than 1 kΩ. If filtering is required, suggested component values are 100 pF differential and 50 Ω on each input; exact values are application-specific.

Additionally, a digital filter is available for the remote temperature measurements to further reduce the effect of noise. This filter is programmable and has two levels when enabled. Level 1 performs a moving average of four consecutive samples. Level 1 filtering can be achieved by setting the digital filter control register (read address 24h, write address 24h) to 01h. Level 2 performs a moving average of eight consecutive samples. Level 2 filtering can be achieved by setting the digital filter control register (read address 24h, write address 24h) to 02h. The value stored in the remote temperature result register is the output of the digital filter, and is the value that the ALERT and THERM limits are compared to. The digital filter provides additional immunity to noise and spikes on the ALERT and THERM outputs. The filter responses to impulse and step inputs are shown in Figure 11 and Figure 12, respectively. The filter can be enabled or disabled by programming the desired levels in the digital filter register; see Table 5. The digital filter is disabled by default and on POR.

TMP461-SP ai_filterresp_impulse_sbos722.gif
Figure 11. Filter Response to Impulse Inputs
TMP461-SP ai_filterresp_step_sbos722.gif
Figure 12. Filter Response to Step Inputs