9.2.2.2 Detailed Design Procedure

For this application, the INA253 measures current flowing through the speaker from the CLASS-D amplifier. The integrated shunt of 2 mΩ with an inductance of only 3 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 INA253 is setup in a bidirectional with the reference set to mid-supply as shown in Figure 37. The power supply to INA253 is setup at 5 V. The output of INA253 is set at 2.5 V. The INA253 with a gain of 100 mV/A, the INA253 output for a peak to peak of 10-A current the output of the INA253 will swing from 3.5 V to 1.5 V. The output can be directly connected to ADC input that has a full scale range of 5 V. The INA253 has a low THD+N of 0.1% at 1 kHz that enables distortion measurement of speaker. The INA253 can measure the impedance of the speaker and accurately measure the resonance frequency and peak impedance at resonance frequency. The INA253 can accurately track changes in impedance real time.