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tida-00874 PVDD Voltage and Current

Marty Zanfino
Prodigy 220 points
Other Parts Discussed in Thread: PCM5242

This amplifier reference design measures impressively well. I'm impressed, but have 2 questions. It drives approx. 80 Watts per channel into 4 Ohms at the threshold of clipping. The peak voltage at this threshold is approx. 25.3 Volts. Why was a 36 Volt PVD selected? Would the distortion be significantly higher with a PVDD at few Volts above the clipping threshold? Or, was the higher PVDD chosen so that the power supply could have less-precise regulation? 

Also, why were 7uH amplifier output inductors chosen instead of the 15uH or 22uH values used in many of your eval boards? Does this particular design require less filtering for similarly low EMI?

Thanks,

Marty

  • 0
    TI__Mastermind 34665 points

    Hi Marty,

    Great observation on the clipping. The TPA3251D2 by itself starts clipping ~100W/4-Ohms. The clipping at 80W/4-Ohms observed TIDA-0087 is from the DAC in the PCM5242. PVDD nominal for TPA3251D2 is 36V and was the main reason it was selected and the best way to compare system performance to TPA3251D2 d/s performance.

    7uH was used based on it gave better THD+N performance vs. 10uH, but had higher idle loss. Definitely the inductor selection should be based on frequency response, idle loss and EMI specific to each application. 

  • 0 in reply to Damian Lewis
    Prodigy 220 points

    Damian, thanks for the quick reply. No further questions at this time.  -Marty