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TPA6404-Q1: power supply decoupling capacitor

Jiang Boqian
Intellectual 655 points
Part Number: TPA6404-Q1

Hi TI expert,

I am using TPA6404 in a automotive infotainment product, this speaker PA in integrated in a head unit PAD, the PCB area is very restricted and height is small.

My question is, I see that TPA6404 is a closed loop class D amplifier, it has 75dB PSRR. So can I lower the bulk decoupling capacitance? On TPA6404 EVM, it uses 330uF. Can I use, say 220uF or even 100uF?

If I use only 100uF, what specification will be influenced, THD?

Thank you.

  • 0
    TI__Mastermind 23310 points

    Hi Jiang,

    We recommend using a 330uF capacitor for a reason. If you use a lower valued bulk capacitor, we can't guarantee the device will have the same performance as stated in the datasheet.

    This is very much a system level question. There could be other capacitance throughout your PVDD line that would still be able to supply the the amplifier with charges during times of high power on the outputs. This is speculative on my side. If you want to know I'd recommend experimenting and seeing what works best for you! :) 

    Best Regards,

    Robert Clifton

  • 0 in reply to Robert Clifton56
    Intellectual 655 points

    Robert,

    Thanks for the reply. I agree with you, and I will experiment by using 100uF. But can you tell me what specification or parameter will be degraded? I don't know what to test right now...

  • 0 in reply to Jiang Boqian
    TI__Mastermind 23310 points

    Hi Jiang,

    I've only ran this experiment on one of our higher power devices. But one of the things I found was during very high power output the THD+N would rise. This was very easily seen on a THD+N vs Power curve. I'm not saying you will experience the same issue of course.

    I think plotting THD+N vs Power would be a good starting point in evaluating the device's performance under different bulk capacitors. 

    Best Regards,

    Robert Clifton

  • 0 in reply to Robert Clifton56
    Intellectual 655 points

    Robert,

    Thank you, I will give it a try. I may have some questions about how to test THD+N, but that's another question...

    Jiang Boqian