SLOS974A June   2021  – March 2023 INA254

PRODUCTION DATA  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Device Comparison
  6. 6 Pin Configuration and Functions
  7. 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 Typical Characteristics
  8. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1 Integrated Shunt Resistor
      2. 8.3.2 Short-Circuit Duration
      3. 8.3.3 Temperature Stability
      4. 8.3.4 Enhanced PWM Rejection Operation
      5. 8.3.5 Input Signal Bandwidth
    4. 8.4 Device Functional Modes
      1. 8.4.1 Adjusting the Output Midpoint With the Reference Pins
      2. 8.4.2 Reference Pin Connections for Unidirectional Current Measurements
      3. 8.4.3 Ground Referenced Output
      4. 8.4.4 Reference Pin Connections for Bidirectional Current Measurements
        1. 8.4.4.1 Output Set to External Reference Voltage
      5. 8.4.5 Output Set to Mid-Supply Voltage
      6. 8.4.6 Output Set to Mid-External Reference
      7. 8.4.7 Output Set Using Resistor Divider
  9. 9 Application and Implementation
    1. 9.1 Application Information
      1. 9.1.1 Input Filtering
    2. 9.2 Typical Applications
      1. 9.2.1 Speaker Enhancements and Diagnostics Using Current Sense Amplifier
        1. 9.2.1.1 Design Requirements
        2. 9.2.1.2 Detailed Design Procedure
        3. 9.2.1.3 Application Curve
    3. 9.3 Power Supply Recommendations
    4. 9.4 Layout
      1. 9.4.1 Layout Guidelines
      2. 9.4.2 Layout Example
  10. 10Device and Documentation Support
    1. 10.1 Device Support
      1. 10.1.1 Development Support
    2. 10.2 Documentation Support
      1. 10.2.1 Related Documentation
    3. 10.3 Receiving Notification of Documentation Updates
    4. 10.4 Support Resources
    5. 10.5 Trademarks
    6. 10.6 Electrostatic Discharge Caution
    7. 10.7 Glossary
  11. 11Mechanical, Packaging, and Orderable Information

9.2.1.2 Detailed Design Procedure

For this application, the INA254 measures current flowing through the speaker from the CLASS-D amplifier. The integrated shunt of 400 µΩ with an inductance of only 2 nH is an excellent choice for current sensing in speaker applications where low inductance is required. The low-inductive shunt enables accurate current sensing across frequencies over the audio range of 20 Hz to 20 kHz.

The INA254 is setup to support bidirectional currents with the reference set to mid-supply as shown in Figure 8-9. When the power supply to the INA254 is set at 3.3 V and there is no current flowing in the speaker, the output of INA254 is at 1.65 V. When operating with a gain of 75 mV/A with peak-to-peak current of ±15 A, the output of the INA254 will swing from 0.525 V to 2.775 V. In this application the output can be directly connected to an ADC input that has a full scale range of 3.3 V. The INA254 has a low THD+N of 0.1% at 1 kHz that enables distortion measurement of speaker. The INA254 can measure the impedance of the speaker and accurately measure the resonance frequency and peak impedance at resonance frequency. The INA254 can accurately track changes in the impedance in real-time.