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PCM5101A: Application question about PCM5101A

Gabriel Xu
Intellectual 2085 points
Part Number: PCM5101A
Other Parts Discussed in Thread: PCM5101, PCM5100A

Hi, teams, this is Gabriel Xu from South China OEM team, nice to meet you.

My customer is designing a new project with differential output device AK4385 and I trying to replace it with PCM5101A. (The audio amplifier is TPA3116)

I wondering to know:

  1. What should be paid attention to when we replace a differential output device with single-ended output?
  2. For analog output voltage we list 2.1*Vrms, i wondering to know the meaning of "Vrms"?
  3. Do we have any sell point could highlight to customer about PCM5101?

Thanks in advance.

  • 0
    TI__Guru 53333 points

    Hi Gabriel,

    1. This mostly depends on what amplifier on the output wants to do with it.  Technically your input magnitude is changing. The AK device will have an input of 5.5Vpp if they are using an 5V supply, where as the PCM510xA will have about 6Vpp.  The one input of the amplifier will not be used, so that input will need to be terminated with matching impedance as the one that is being used.  See below:

    2.  VRMS is Volts root-mean-square, can is commonly used for power calculations.  It is fairly popular to use VRMS instead of VPP in audio applications.  2.1VRMS = ~6Vpp.

    3. The best selling points for the PCM510xA devices is that it has a integrated PLL, meaning the high frequency SCK I2S signal may not be necessary.  This signal is difficult to generated in some applications.  The output is also 'DirectPath', meaning that it centered around GND rather than 2.5V like the AK device, though that is not very critical in this application.  It also uses an advanced delta-sigma modulator architecture that uses noise shaping techniques to move the output of band noise that is inherent with all DSM type DACs further away from the audible band.  The AK device recommends a second order active filter to attenuate this noise.  Our device only requires a simple 1st order RC to attenuate the noise to an acceptable level.  

    Please feel free to email me specifics of the customer if you want more inputs as well. 

    Thanks,

    Paul

  • 0 in reply to Paul_Frost
    TI__Intellectual 2085 points
    Hi Paul
    Thanks for your comments it's very clear and helpful for me to promote our device.
    I also want to double confirm with you about some details. As you mention PCM5100A could output up to 6Vpp under 3.3V AVDD, why it could achieve this is because we centtered the output around GND and our deivce could generate output from AVDD~(-AVDD) . Am i right?
    It's a very cool feature.
    About matching impedance method you mean is to add another 1uF cap and 2.2uF cap to tie IN(-) to IN(+). Am i right?
    Thanks in advance.
  • 0 in reply to Gabriel Xu
    TI__Guru 53333 points
    Hi Gabriel,

    You are correct, the device generates its own -3.3V supply with a charge pump.

    The 1µF is used to match impedances. The 2.2nF is just the RC filter of the output.

    Thanks!
    Paul