When conducting AC diagnostics, the TAS6424E-Q1 must receive a stable 19kHz, 0dBFS sine wave signal as the excitation source. If the signal frequency output by the front-end DSP or host SoC deviates, or contains excessive harmonic noise, it will directly prevent the chip's internal algorithm from properly locking onto the impedance characteristics. Users must ensure that the 19kHz signal provided by the SoC/DSP is input to the TAS6424E-Q1 via the I2S/TDM interface. The amplitude of the 19kHz excitation signal must be controlled within a reasonable range. If the signal is too weak, the impedance calculation may fluctuate significantly due to an insufficient signal-to-noise ratio (SNR); if the signal is too strong, it may cause output clipping, rendering the diagnostic logic invalid.

It must be ensured that the excitation source frequency is precise and the amplitude is strictly aligned to 0dBFS, while matching the I2S/TDM timing (such as Offset settings) to eliminate digital distortion induced by bit shifts, thereby guaranteeing signal integrity at the source.

Solution: During the initial stage of TAS6424E-Q1 AC diagnostic debugging, it is highly recommended to use a 4.0ohm non-inductive cement resistor (or a precision power resistor) instead of a real loudspeaker for calibration. This is a critical step to ensure the accuracy of the diagnostic algorithm. By accurately verifying the conversion factor between the chip's readback values and the actual ohmic values, developers can adjust the signal frequency and amplitude provided by the DSP, thereby locking in system-level gain accuracy. The correct test results are shown in the table below: