SBOS644C February   2013  – March 2018 INA231

PRODUCTION DATA.  

  1. Features
  2. Applications
  3. Description
    1.     Device Images
      1.      High-or Low-Side Sensing
  4. Revision History
  5. Device Comparison Table
  6. Pin Configuration and Functions
    1.     Pin Functions
  7. Specifications
    1. 7.1 Absolute Maximum Ratings
    2. 7.2 ESD Ratings
    3. 7.3 Recommended Operating Conditions
    4. 7.4 Thermal Information
    5. 7.5 Electrical Characteristics
    6. 7.6 Timing Requirements: I2C Bus
    7. 7.7 Typical Characteristics
  8. Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1 Basic Analog-to-Digital Converter (ADC) Functions
        1. 8.3.1.1 Power Calculation
        2. 8.3.1.2 ALERT Pin
    4. 8.4 Device Functional Modes
      1. 8.4.1 Averaging and Conversion Time Considerations
    5. 8.5 Programming
      1. 8.5.1 Configure, Measure, and Calculate Example
      2. 8.5.2 Programming the Power Measurement Engine
        1. 8.5.2.1 Calibration Register and Scaling
      3. 8.5.3 Simple Current Shunt Monitor Usage (No Programming Necessary)
      4. 8.5.4 Default INA231 Settings
      5. 8.5.5 Writing to and Reading from the INA231
        1. 8.5.5.1 Bus Overview
          1. 8.5.5.1.1 Serial Bus Address
          2. 8.5.5.1.2 Serial Interface
        2. 8.5.5.2 High-Speed I2C Mode
      6. 8.5.6 SMBus Alert Response
    6. 8.6 Register Maps
      1. Table 3. Summary of Register Set
      2. 8.6.1     Configuration Register (00h, Read/Write)
        1. Table 4. Configuration Register (00h, Read/Write) Descriptions
        2. 8.6.1.1   AVG Bit Settings [11:9]
          1. Table 5. AVG Bit Settings [11:9] Description
        3. 8.6.1.2   VBUS CT Bit Settings [8:6]
          1. Table 6. VBUS CT Bit Settings [8:6] Description
        4. 8.6.1.3   VSH CT Bit Settings [5:3]
          1. Table 7. Register Description VSH CT Bit Settings [5:3]
        5. 8.6.1.4   Mode Settings [2:0]
          1. Table 8. Mode Settings [2:0]
      3. 8.6.2     Shunt Voltage Register (01h, Read-Only)
        1. Table 9. Shunt Voltage Register (01h, Read-Only) Description
      4. 8.6.3     Bus Voltage Register (02h, Read-Only)
        1. Table 10. Bus Voltage Register (02h, Read-Only) Description
      5. 8.6.4     Power Register (03h, Read-Only)
        1. Table 11. Power Register (03h, Read-Only) Description
      6. 8.6.5     Current Register (04h, Read-Only)
        1. Table 12. Current Register (04h, Read-Only) Description
      7. 8.6.6     Calibration Register (05h, Read/Write)
        1. Table 13. Calibration Register (05h, Read/Write) Description
      8. 8.6.7     Mask/Enable Register (06h, Read/Write)
        1. Table 14. Mask/Enable Register (06h, Read/Write) Description
      9. 8.6.8     Alert Limit Register (07h, Read/Write)
        1. Table 15. Alert Limit Register (07h, Read/Write) Description
  9. Application and Implementation
    1. 9.1 Application Information
      1. 9.1.1 Filtering and Input Considerations
    2. 9.2 Typical Applications
      1. 9.2.1 Design Requirements
      2. 9.2.2 Detailed Design Procedure
      3. 9.2.3 Application Curves
  10. 10Power Supply Recommendations
  11. 11Layout
    1. 11.1 Layout Guidelines
    2. 11.2 Layout Example
  12. 12Device and Documentation Support
    1. 12.1 Documentation Support
      1. 12.1.1 Related Documentation
    2. 12.2 Receiving Notification of Documentation Updates
    3. 12.3 Community Resources
    4. 12.4 Trademarks
    5. 12.5 Electrostatic Discharge Caution
    6. 12.6 Glossary
  13. 13Mechanical, Packaging, and Orderable Information

Package Options

Refer to the PDF data sheet for device specific package drawings

Mechanical Data (Package|Pins)
  • YFF|12
  • YFD|12
Thermal pad, mechanical data (Package|Pins)
Orderable Information

Programming

An important aspect of the INA231 is that it does not necessarily measure current or power. The INA231 measures both the differential voltage applied between the IN+ and IN– input pins and the voltage applied to the BUS pin. In order for the INA231 to report both current and power values, both the Current register resolution and the value of the shunt resistor present in the application that resulted in the differential voltage being developed must be programmed. The Power register is internally set to be 25 times the programmed least significant bit of the Current register (Current_LSB). Both the Current_LSB and shunt resistor value are used when calculating the Calibration register value. The INA231 uses this value to calculate the corresponding current and power values based on the measured shunt and bus voltages.

The Calibration register is calculated based on Equation 1. This equation includes the term Current_LSB, the programmed value for the LSB for the Current register. This is the value used to convert the value in the Current register to the actual current in amps. The highest resolution for the Current register can be obtained by using the smallest allowable Current_LSB based on the maximum expected current, as shown in Equation 2. While this value yields the highest resolution, it is common to select a value for the Current_LSB to the nearest round number above this value to simplify the conversion of the Current register and Power register to amps and watts, respectively. RSHUNT is the value of the external shunt used to develop the differential voltage across the input pins. The 0.00512 value in Equation 1 is an internal fixed value used to make sure that scaling is properly maintained.

Equation 1. INA231 q_cal_curr_lsb_bos547.gif
Equation 2. INA231 q_min_curr_lsb_bos547.gif

After the Calibration register has been programmed, the Current register and Power register are updated accordingly based on the corresponding shunt voltage and bus voltage measurements. Until the Calibration register is programmed, the Current and Power registers remain at zero.