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Q: TAS5612PHD output voltage fluctuation
A customer told us that they found TAS5612's output fluctuated when they changed PVDD in spite of TAS5612 'local feedback'. All input signal conditions are 1kHz/20dB sine wave.
Could you let me know if it is a correct behavior?
A: RE: TAS5612PHD output voltage fluctuation
PWM devices like TAS5612 use feedback in the audio band to reduce distortion and output impedance and to improve PSRR, as specified in the data sheets. However, there is power supply voltage feedback that is filtered to react only to changes near DC. This makes it possible to use power supply volume control with these devices. (Of course, this is possible with open loop power stages with PWM inputs.)
So TAS5612 will provide the performance shown in the data sheet, but it can also be used with power supply volume control. That is what the customer sees.
Q: RE: TAS5612PHD output voltage fluctuation
You are correct. The behavior is PSVC. (This means TAS5612 has no DC PSRR - however, its AC PSRR is still very good, because the local feedback applies in the AC range.)
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