SBAU206B april   2015  – may 2023 ADS1262 , ADS1263

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1EVM Overview
    1. 1.1 ADS1263EVM Kit
    2. 1.2 ADS1263EVM Board
  5. 2Getting Started With the ADS1263EVM
  6. 3Analog Interface
    1. 3.1 Analog Input Options
      1. 3.1.1 ADS1263 Integrated Input Functions
        1. 3.1.1.1 ADC Inputs
        2. 3.1.1.2 IDAC Output
        3. 3.1.1.3 VBIAS Output
        4. 3.1.1.4 External Reference
        5. 3.1.1.5 Test DAC Output
        6. 3.1.1.6 GPIO
      2. 3.1.2 Analog Sensor Connections
        1. 3.1.2.1 Connecting a Thermocouple to J4 on the ADS1263EVM
        2. 3.1.2.2 Connecting a Thermistor to J3 on the ADS1263EVM
        3. 3.1.2.3 Using Thermistor RT1 for Thermocouple Cold-Junction Compensation
        4. 3.1.2.4 Connecting an RTD to J3 on the ADS1263EVM
          1. 3.1.2.4.1 Connecting a 2-Wire RTD
          2. 3.1.2.4.2 Connecting a 3-Wire RTD
          3. 3.1.2.4.3 Connecting a 4-Wire RTD
    2. 3.2 ADC Connections and Decoupling
    3. 3.3 Clocking
    4. 3.4 Voltage Reference
  7. 4Digital Interface
  8. 5Power Supplies
  9. 6Software Installation
  10. 7EVM Operation and GUI
    1. 7.1 Connecting the EVM Hardware
    2. 7.2 EVM GUI Global Settings for ADC Control
    3. 7.3 Time Domain Display
    4. 7.4 Frequency Domain Display
    5. 7.5 Histogram Display
    6. 7.6 Using the GUI to Control ADC2
  11. 8Bill of Materials, PCB Layout, and Schematics
    1. 8.1 Bill of Materials
    2. 8.2 PCB Layout
    3. 8.3 Schematics
  12. 9Revision History

3.1.2.3 Using Thermistor RT1 for Thermocouple Cold-Junction Compensation

The ADS1263EVM includes provisions for using a PCB-mounted thermistor to measure the cold junction of a thermocouple connected to the AIN8 and AIN9 inputs on J4. Figure 3-6 shows how top- and bottom-layer copper pours create an isothermal bridge between the AIN8 and AIN9 inputs. This bridge helps make sure that thermistor RT1 measures the same temperature as the thermocouple cold junction at inputs J4:1 and J4:2, enabling a more accurate thermocouple measurement.

GUID-20221111-SS0I-XM9V-N3NW-92NKSVKSDRFR-low.png Figure 3-6 PCB Layout for J4 Showing Copper Pours for CJC Measurements

As discussed in Section 3.1.2.2, thermistor RT1 is not populated by default on the ADS1263EVM. Choose a 10-kΩ NTC thermistor in a 0603 package for this component. Additionally, populate the 10-kΩ bias resistor (R34) to create a valid resistor divider as well as the 0-Ω resistor (R36) to directly bias the sensor using the 2.5-V reference output of the ADS1263. Populating the linearization resistor (R33) is optional.

Measure the thermistor voltage as described in Section 3.1.2.2. However, note that the ADS1263 is a multiplexed ADC that can only measure one single-ended or differential input per conversion cycle. As a result, the thermocouple and CJC measurements must be taken separately and then manipulated in software to determine the resulting temperature. To learn more about CJC as well as how to use this value to determine the true measured temperature, see the A Basic Guide to Thermocouple Measurements application note.