SBOSAC1A July   2023  – December 2023 INA740A , INA740B

PRODMIX  

  1.   1
  2. Features
  3. Applications
  4. Description
  5. Pin Configuration and Functions
  6. Specifications
    1. 5.1 Absolute Maximum Ratings
    2. 5.2 ESD Ratings
    3. 5.3 Recommended Operating Conditions
    4. 5.4 Thermal Information
    5. 5.5 Electrical Characteristics
    6. 5.6 Timing Requirements (I2C)
    7. 5.7 Timing Diagram
    8. 5.8 Typical Characteristics
  7. Detailed Description
    1. 6.1 Overview
    2. 6.2 Functional Block Diagram
    3. 6.3 Feature Description
      1. 6.3.1 Integrated Shunt Resistor
      2. 6.3.2 Safe Operating Area
      3. 6.3.3 Versatile High Voltage Measurement Capability
      4. 6.3.4 Internal Measurement and Calculation Engine
      5. 6.3.5 High-Precision Delta-Sigma ADC
        1. 6.3.5.1 Low Latency Digital Filter
        2. 6.3.5.2 Flexible Conversion Times and Averaging
      6. 6.3.6 Integrated Precision Oscillator
      7. 6.3.7 Multi-Alert Monitoring and Fault Detection
    4. 6.4 Device Functional Modes
      1. 6.4.1 Shutdown Mode
      2. 6.4.2 Power-On Reset
    5. 6.5 Programming
      1. 6.5.1 I2C Serial Interface
        1. 6.5.1.1 Writing to and Reading Through the I2C Serial Interface
        2. 6.5.1.2 High-Speed I2C Mode
        3. 6.5.1.3 SMBus Alert Response
  8. Application and Implementation
    1. 7.1 Application Information
      1. 7.1.1 Device Measurement Range and Resolution
      2. 7.1.2 ADC Output Data Rate and Noise Performance
    2. 7.2 Typical Application
      1. 7.2.1 Design Requirements
      2. 7.2.2 Detailed Design Procedure
        1. 7.2.2.1 Configure the Device
        2. 7.2.2.2 Set Desired Fault Thresholds
        3. 7.2.2.3 Calculate Returned Values
      3. 7.2.3 Application Curves
    3. 7.3 Power Supply Recommendations
    4. 7.4 Layout
      1. 7.4.1 Layout Guidelines
      2. 7.4.2 Layout Example
    5. 7.5 Register Maps
      1. 7.5.1 INA740x Registers
  9. Device and Documentation Support
    1. 8.1 Receiving Notification of Documentation Updates
    2. 8.2 Support Resources
    3. 8.3 Trademarks
    4. 8.4 Electrostatic Discharge Caution
    5. 8.5 Glossary
  10. Revision History
  11. 10Mechanical, Packaging, and Orderable Information

Package Options

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

Integrated Shunt Resistor

The INA740x is a precise, low-drift, digital power monitor that provides accurate measurements over the entire specified ambient temperature range of –40°C to +125°C. The integrated current-sensing resistor is internally compensated to provide measurement stability over temperature, while simplifying printed circuit board (PCB) layout and size constraints.

Access to the on-chip current-sensing resistor is provided by the IS+ and IS- pins. This resistor features internal sense connections that are brought out on the SH+ and SH- pins. Access to the digital power monitor is provided by the IN+ and IN- pins. When the shunt sense connections are connected to the digital power monitor inputs, the sensed voltage is calibrated and temperature compensated to achieve a high level of accuracy. The construction of this resistor does not allow it to be used as a stand-alone component for accurate current measurement. The INA740x is system-calibrated to ensure that the current-sensing resistor and digital power monitor are both precisely matched to one another.

The nominal pin-to-pin resistance from IS+ to IS- is approximately 1 mΩ, while the internal resistance seen by the SH+ and SH- pins is nominally 800 μΩ. The power dissipation requirements of the system and package are based on the total package resistance between the IS+ and IS– pins.

GUID-20231121-SS0I-94DP-GZ8L-GDB0T2M7JXXB-low.svgFigure 6-1 IS+ to IS– Package Resistance vs Temperature

The internal compensation of the INA740x corrects for pin-to-pin resistance increases with temperature, achieving low drift over the ambient temperature range.

The INA740x is most accurate when measuring currents around 15 A to 20 A. As currents increase, the error in the current measurement also increases. Figure 6-2 shows how the gain error of the INA740x varies with the shunt current for all device options.

GUID-20231121-SS0I-JMMM-CLBJ-92SL7GHM2LHD-low.svgFigure 6-2 Gain Error vs Shunt Current

The shape of this curve will vary some based on the PCB design. Designs with better thermal performance will generally flatten this curve.

The temperature coefficient of the shunt is compensated by sampling the junction temperature and internally applying a correction factor based on this temperature to the reported current measurements. During transient currents, the shunt heats faster than the temperature sensor. This temporary difference in temperatures results in higher values in the reported current until the temperature stabilizes. Figure 6-3 shows the sampled output response during a current step from 0A to 22.5 A

GUID-20231120-SS0I-WQ4N-H0XN-2QKPF7QN6NK6-low.svgFigure 6-3 Device Current Transient Overshoot

The transient overshoot is similar to what would be seen in analog output current sense amplifiers. It is important to understand this overshoot exists when setting an overcurrent alert threshold in order to avoid false triggers.