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PCM2704: Capacitor Selection between DAC and Amplifier

Steven Yan
Intellectual 840 points
Part Number: PCM2704
Other Parts Discussed in Thread: TPA3138D2

Greetings,

My customer is planning to use the TPA3138D2 amplifier with the PCM2704 DAC and they have a question regarding the series capacitors to use between the DAC and the amplifier.

"On the PCM2704 datasheet, 100uF and 1uF are used, but on the PCM2704 EVM, only a 100uF is used in reverse polarity.

On the TPA3138D2 datasheet, a 1uF ceramic capacitor is used.

In our design, the DAC and the amplifier will be on the same PCB and everything willl be powered using the USB +5V power.

Could you please give me more information on the capacitors value/polarity that we should use in our design?"

PCM2704 datasheet:

 PCM2704 EVM:

TPA3138D2 datasheet:

Our audio team has confirmed for the TPA3138, a 1uF DC cap is fine. Looking forward to your response.

Best,

Steven

  • 0
    TI__Mastermind 19350 points

    Hi Steven, The value of C is more critical for the TPA3138  , as it directly affects the bass (low-frequency) performance of the amplifier you are attaching to PCM. The TPA3138 has a fixed input Z. I think a 1uf should be okay for PCM too .  It is all depending on frequency response you need. For polarity please use the below diagram (fig 33, page 29 of data sheet)