SBOS576C May   2012  – September 2025 INA3221

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Device Comparison Table
  6. 5 Pin Configuration and Functions
  7. 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
  8. 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
      2. 7.3.2 Alert Monitoring
        1. 7.3.2.1 Critical Alert
          1. 7.3.2.1.1 Summation Control Function
        2. 7.3.2.2 Warning Alert
        3. 7.3.2.3 Power-Valid Alert
        4. 7.3.2.4 Timing-Control Alert
        5. 7.3.2.5 Default Settings
      3. 7.3.3 Software Reset
    4. 7.4 Device Functional Modes
      1. 7.4.1 Averaging Function
      2. 7.4.2 Multiple Channel Monitoring
        1. 7.4.2.1 Channel Configuration
        2. 7.4.2.2 Averaging and Conversion-Time Considerations
      3. 7.4.3 Filtering and Input Considerations
    5. 7.5 Programming
      1. 7.5.1 Bus Overview
        1. 7.5.1.1 Serial Bus Address
        2. 7.5.1.2 Serial Interface
      2. 7.5.2 Writing To and Reading From the INA3221
        1. 7.5.2.1 High-Speed I2C Mode
      3. 7.5.3 SMBus Alert Response
    6. 7.6 Register Maps
      1. 7.6.1 Summary of Register Set
      2. 7.6.2 Register Descriptions
        1. 7.6.2.1  Configuration Register (address = 00h) [reset = 7127h]
        2. 7.6.2.2  Channel-1 Shunt-Voltage Register (address = 01h), [reset = 00h]
        3. 7.6.2.3  Channel-1 Bus-Voltage Register (address = 02h) [reset = 00h]
        4. 7.6.2.4  Channel-2 Shunt-Voltage Register (address = 03h) [reset = 00h]
        5. 7.6.2.5  Channel-2 Bus-Voltage Register (address = 04h) [reset = 00h]
        6. 7.6.2.6  Channel-3 Shunt-Voltage Register (address = 05h) [reset = 00h]
        7. 7.6.2.7  Channel-3 Bus-Voltage Register (address = 06h) [reset = 00h]
        8. 7.6.2.8  Channel-1 Critical-Alert Limit Register (address = 07h) [reset = 7FF8h]
        9. 7.6.2.9  Warning-Alert Channel-1 Limit Register (address = 08h) [reset = 7FF8h]
        10. 7.6.2.10 Channel-2 Critical-Alert Limit Register (address = 09h) [reset = 7FF8h]
        11. 7.6.2.11 Channel-2 Warning-Alert Limit Register (address = 0Ah) [reset = 7FF8h]
        12. 7.6.2.12 Channel-3 Critical-Alert Limit Register (address = 0Bh) [reset = 7FF8h]
        13. 7.6.2.13 Channel-3 Warning-Alert Limit Register (address = 0Ch) [reset = 7FF8h]
        14. 7.6.2.14 Shunt-Voltage Sum Register (address = 0Dh) [reset = 00h]
        15. 7.6.2.15 Shunt-Voltage Sum-Limit Register (address = 0Eh) [reset = 7FFEh]
        16. 7.6.2.16 Mask/Enable Register (address = 0Fh) [reset = 0002h]
        17. 7.6.2.17 Power-valid Upper-limit Register (address = 10h) [reset = 2710h]
        18. 7.6.2.18 Power-Valid Lower-Limit Register (address = 11h) [reset = 2328h]
        19. 7.6.2.19 Manufacturer ID Register (address = FEh) [reset = 5449h]
        20. 7.6.2.20 Die ID Register (address = FFh) [reset = 3220]
  9. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Application
      1. 8.2.1 Design Requirements
      2. 8.2.2 Detailed Design Procedure
      3. 8.2.3 Application Curves
    3. 8.3 Power Supply Recommendations
    4. 8.4 Layout
      1. 8.4.1 Layout Guidelines
      2. 8.4.2 Layout Example
  10. 9 Device and Documentation Support
    1. 9.1 Device Support
      1. 9.1.1 Development Support
    2. 9.2 Documentation Support
      1. 9.2.1 Related Documentation
    3. 9.3 Receiving Notification of Documentation Updates
    4. 9.4 Support Resources
    5. 9.5 Trademarks
    6. 9.6 Electrostatic Discharge Caution
    7. 9.7 Glossary
  11. 10Revision History
  12. 11Mechanical, Packaging, and Orderable Information

7.4.2.2 Averaging and Conversion-Time Considerations

The INA3221 has programmable conversion times for both the shunt- and bus-voltage measurements. The selectable conversion times for these measurements range from 140μs to 8.244ms. The conversion-time settings, along with the programmable-averaging mode, enable the INA3221 to optimize available timing requirements in a given application. For example, if a system requires data to be read every 2ms with all three channels monitored, configure the INA3221 with the conversion times for the shunt- and bus-voltage measurements set to 332μs.

The INA3221 can also be configured with a different conversion-time setting for the shunt- and bus-voltage measurements. This approach is common in applications where the bus voltage tends to be relatively stable, and allows for the time focused on the bus voltage measurement to be reduced relative to the shunt-voltage measurement. For example, the shunt-voltage conversion time can be set to 4.156ms with the bus-voltage conversion time set to 588μs for a 5ms update time.

There are trade-offs associated with the conversion-time and averaging-mode settings. The averaging feature significantly improves the measurement accuracy by effectively filtering the signal. This approach allows the INA3221 to reduce the amount of noise in the measurement caused by noise coupling into the signal. A greater number of averages allows the INA3221 to be more effective in reducing the measurement noise component. The trade-off to this noise reduction is that the averaged value has a longer response time to input-signal changes. This aspect of the averaging feature is mitigated to some extent with the critical-alert feature that compares each single conversion to determine if a measured signal (with noise component) has exceeded the maximum acceptable level.

The selected conversion times also have an impact on measurement accuracy. This effect can seen in Figure 7-7. The multiple conversion times shown in Figure 7-7 illustrate the impact of noise on measurement. These curves shown do not use averaging. to achieve the highest-accuracy measurement possible, use a combination of the longest allowable conversion times and highest number of averages, based on system timing requirements.

INA3221 Noise Versus Conversion TimeFigure 7-7 Noise Versus Conversion Time