SBOS743A July   2015  – May 2020 INA226-Q1

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
    1.     Device Images
      1.      High-Side or Low-Side Sensing Application
  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 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 Basic ADC Functions
        1. 7.3.1.1 Power Calculation
        2. 7.3.1.2 Alert Pin
    4. 7.4 Device Functional Modes
      1. 7.4.1 Averaging and Conversion Time Considerations
      2. 7.4.2 Filtering and Input Considerations
    5. 7.5 Programming
      1. 7.5.1 Programming the Calibration Register
      2. 7.5.2 Programming the Power Measurement Engine
        1. 7.5.2.1 Calibration Register and Scaling
      3. 7.5.3 Simple Current Shunt Monitor Usage (No Programming Necessary)
      4. 7.5.4 Default Settings
      5. 7.5.5 Bus Overview
        1. 7.5.5.1 Serial Bus Address
        2. 7.5.5.2 Serial Interface
        3. 7.5.5.3 Writing to and Reading from the INA226-Q1
          1. 7.5.5.3.1 High-Speed I2C Mode
        4. 7.5.5.4 SMBus Alert Response
    6. 7.6 Register Maps
      1. Table 4. Register Set Summary
      2. 7.6.1    Configuration Register (00h) (Read/Write)
        1. Table 5. Configuration Register (00h) (Read/Write) Descriptions
      3. 7.6.2    Shunt Voltage Register (01h) (Read-Only)
        1. Table 10. Shunt Voltage Register (01h) (Read-Only) Description
      4. 7.6.3    Bus Voltage Register (02h) (Read-Only)
        1. Table 11. Bus Voltage Register (02h) (Read-Only) Description
      5. 7.6.4    Power Register (03h) (Read-Only)
        1. Table 12. Power Register (03h) (Read-Only) Description
      6. 7.6.5    Current Register (04h) (Read-Only)
        1. Table 13. Current Register (04h) (Read-Only) Register Description
      7. 7.6.6    Calibration Register (05h) (Read/Write)
        1. Table 14. Calibration Register (05h) (Read/Write) Description
      8. 7.6.7    Mask/Enable Register (06h) (Read/Write)
        1. Table 15. Mask/Enable Register (06h) (Read/Write)
      9. 7.6.8    Alert Limit Register (07h) (Read/Write)
        1. Table 16. Alert Limit Register (07h) (Read/Write) Description
      10. 7.6.9    Manufacturer ID Register (FEh) (Read-Only)
        1. Table 17. Manufacturer ID Register (FEh) (Read-Only) Description
      11. 7.6.10   Die ID Register (FFh) (Read-Only)
        1. Table 18. Die ID Register (FFh) (Read-Only) Description
  8. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Applications
      1. 8.2.1 High-Side Sensing Circuit Application
        1. 8.2.1.1 Design Requirements
        2. 8.2.1.2 Detailed Design Procedure
        3. 8.2.1.3 Application Curves
          1. Table 19. Configuration Register (00h) Settings for (Value = 4025h)
          2. Table 20. Configuration Register (00h) Settings for (Value = 4005h)
          3. Table 21. Mask/Enable Register (06h) Settings for and (Value = 8000h)
          4. Table 22. Alert Limit Register (07h) Settings for and (Value = 7D00)
  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 Device Support
      1. 11.1.1 Development Support
    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

7.5 Programming

An important aspect of the INA226-Q1 device is that it does not necessarily measure current or power. The device measures both the differential voltage applied between the IN+ and IN- input pins and the voltage applied to the VBUS pin. In order for the device to report both current and power values, the user must program the resolution of the Current Register (04h) and the value of the shunt resistor present in the application to develop the differential voltage applied between the input pins. The Power Register (03h) is internally set to be 25 times the programmed Current_LSB. Both the Current_LSB and shunt resistor value are used in the calculation of the Calibration Register value the device uses 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, which is the programmed value for the LSB for the Current Register (04h). The user uses this value to convert the value in the Current Register (04h) to the actual current in amperes. The highest resolution for the Current Register (04h) 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 (04h) and Power Register (03h) to amperes and watts respectively. The RSHUNT term is the value of the external shunt used to develop the differential voltage across the input pins.

Equation 1. INA226-Q1 q_cal_curr_lsb_bos547.gif

where

  • 0.00512 is an internal fixed value used to ensure scaling is maintained properly
Equation 2. INA226-Q1 q_min_curr_lsb_bos547.gif

After programming the Calibration Register, the Current Register (04h) and Power Register (03h) update accordingly based on the corresponding shunt voltage and bus voltage measurements. Until the Calibration Register is programmed, the Current Register (04h) and Power Register (03h) remain at zero.