7.2.2.2 Detailed Design Procedure

For this application, the INA790x measures current flowing through the speaker from the CLASS-D amplifier.

The integrated shunt of 400µΩ with an inductance of only 2nH 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 20Hz to 20kHz.

The INA790x is setup to support bidirectional currents with the reference set to mid-supply as shown in Output

Set to Mid-Supply Voltage. When the power supply to the INA790x is set at 3.3V and there is no current flowing

in the speaker, the output of INA790x is at 1.65V. When operating with a gain of 80mV/A with peak-to-peak

current of ±15A, the output of the INA790x swings from 0.45V to 2.85V. In this application the output can be

directly connected to an ADC input that has a full scale range of 3.3V. The INA790x can measure the impedance

of the speaker and accurately measure the resonance frequency and peak impedance at resonance frequency.

The INA790x can accurately track changes in the impedance in real-time.

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INA790A, INA790B

SBOSAA6B – MAY 2024 – REVISED JULY 2025

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