SLYS023A December   2020  – May 2022 INA229

PRODUCTION DATA  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Pin Configuration and 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 Timing Requirements (SPI)
    7. 6.7 Timing Diagram
    8. 6.8 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 Versatile High Voltage Measurement Capability
      2. 7.3.2 Internal Measurement and Calculation Engine
      3. 7.3.3 Low Bias Current
      4. 7.3.4 High-Precision Delta-Sigma ADC
        1. 7.3.4.1 Low Latency Digital Filter
        2. 7.3.4.2 Flexible Conversion Times and Averaging
      5. 7.3.5 Shunt Resistor Drift Compensation
      6. 7.3.6 Integrated Precision Oscillator
      7. 7.3.7 Multi-Alert Monitoring and Fault Detection
    4. 7.4 Device Functional Modes
      1. 7.4.1 Shutdown Mode
      2. 7.4.2 Power-On Reset
    5. 7.5 Programming
      1. 7.5.1 Serial Interface
        1. 7.5.1.1 SPI Frame
    6. 7.6 Register Maps
      1. 7.6.1 INA229 Registers
  8. 8 Application and Implementation
    1. 8.1 Application Information
      1. 8.1.1 Device Measurement Range and Resolution
      2. 8.1.2 Current , Power, Energy, and Charge Calculations
      3. 8.1.3 ADC Output Data Rate and Noise Performance
      4. 8.1.4 Input Filtering Considerations
    2. 8.2 Typical Application
      1. 8.2.1 Design Requirements
      2. 8.2.2 Detailed Design Procedure
        1. 8.2.2.1 Select the Shunt Resistor
        2. 8.2.2.2 Configure the Device
        3. 8.2.2.3 Program the Shunt Calibration Register
        4. 8.2.2.4 Set Desired Fault Thresholds
        5. 8.2.2.5 Calculate Returned Values
      3. 8.2.3 Application Curves
  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 Support Resources
    3. 11.3 Trademarks
    4. 11.4 Electrostatic Discharge Caution
    5. 11.5 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

Package Options

Mechanical Data (Package|Pins)
Thermal pad, mechanical data (Package|Pins)
Orderable Information

7.3.5 Shunt Resistor Drift Compensation

The INA229 device has an internal temperature sensor which can measure die temperature from –40 °C to +125 °C. The accuracy of the temperature sensor is ±2 °C across the operational temperature range. The temperature value is stored inside the DIETEMP register and can be read through the digital interface.

The device has the capability to utilize the temperature measurement to compensate for shunt resistor temperature variance. This feature can be enabled by setting the TEMPCOMP bit in the CONFIG register, while the SHUNT_TEMPCO is the register that can be programmed to enter the temperature coefficient of the used shunt. The full scale value of the SHUNT_TEMPCO register is 16384 ppm/°C. The temperature compensation is referenced to +25 °C . The shunt is always assumed to have a positive temperature coefficient and the temperature compensation follows Equation 1:

Equation 1. GUID-20201116-CA0I-WR1S-5P5W-9BBT56HTNQST-low.gif

where

  • RNOM is the nominal shunt resistance in Ohms at 25 °C.
  • DIETEMP is the temperature value in the DIETEMP register in °C.
  • SHUNT_TEMPCO is the shunt temperature coefficient in ppm/°C.

When this feature is enabled and correctly programmed, the CURRENT register data is corrected by constantly monitoring the die temperature and becomes a function of temperature. The effectiveness of the compensation will depend on how well the resistor and the INA229 are thermally coupled since the die temperature of the INA229 is used for the compensation.

Note:

Warning: If temperature compensation is enabled under some conditions, the calculated current result may be lower than the actual value. This condition typically occurs when there is a high value of shunt voltage ( >70% of full range), there is a shunt with high temperature-coefficient value ( >2000 ppm/°C), and there is a high temperature ( >100°C). Consider the example of constant current flowing through a high temperature coefficient shunt such that at lower temperatures the shunt voltage is in its upper range. As the temperature increases, the device will correctly report a constant current until the maximum shunt voltage is reached. As temperature continues to increase after the maximum shunt voltage is reached, the device will start reporting lower currents. This is because the effective resistance calculated will continue to increase while the detected shunt voltage will remain constant due to the voltage exceeding the selected ADC range.