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

7.4.1 Averaging and Conversion Time Considerations

The INA226-Q1 device offers programmable conversion times (tCT) for both the shunt voltage and bus voltage measurements. The conversion times for these measurements can be selected from as fast as 140 μs to as long as 8.244 ms. The conversion time settings, along with the programmable averaging mode, allow the device to be configured to optimize the available timing requirements in a given application. For example, if a system requires that data be read every 5ms, the device could be configured with the conversion times set to 588 μs for both shunt and bus voltage measurements and the averaging mode set to 4. This configuration results in the data updating approximately every 4.7ms. The device could also be configured with a different conversion time setting for the shunt and bus voltage measurements. This type of approach is common in applications where the bus voltage tends to be relatively stable. This situation can allow for the time focused on the bus voltage measurement to be reduced relative to the shunt voltage measurement. The shunt voltage conversion time could be set to 4.156 ms with the bus voltage conversion time set to 588 μs, with the averaging mode set to 1. This configuration also results in data updating approximately every 4.7 ms.

There are trade-offs associated with the settings for conversion time and the averaging mode used. The averaging feature can significantly improve the measurement accuracy by effectively filtering the signal. This approach allows the device to reduce any noise in the measurement that may be caused by noise coupling into the signal. A greater number of averages enables the device to be more effective in reducing the noise component of the measurement.

The conversion times selected can also have an impact on the measurement accuracy. Figure 20 shows multiple conversion times to illustrate the impact of noise on the measurement. In order to achieve the highest accuracy measurement possible, use a combination of the longest allowable conversion times and highest number of averages, based on the timing requirements of the system.

INA226-Q1 ai_tc_noise_conversion_bos547.gifFigure 20. Noise vs Conversion Time