INA253

REF2

VS

OUT

GND

IN+

IN±

±

REF1

2.7-V to 5.5-V

VDD

23

INA253

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SLOS954A – JULY 2018 – REVISED DECEMBER 2018

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9.2.2 Speaker Enhancements and Diagnostics Using Current Sense Amplifier

CLASS-D audio amplifiers in conjunction with the INA253 provide accurate speaker load current. Speaker load

current is used to determine speaker diagnostics, and can further be expanded to measure key speaker

parameters, such as speaker coil resistance and speaker real-time ambient temperature.

Figure 43. Current Sensing in a CLASS-D Subsystem

9.2.2.1 Design Requirements

Table 3. Design Parameters

DESIGN PARAMETER

EXAMPLE VALUE

Common-mode voltage

24 V

Power-supply voltage

5 V

Maximum rms current

5 A

Frequency sweep

20 Hz to 20 Khz

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.