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PCM5101A: Questions about driving output and dev board schematic

Cameron Wutzke
Intellectual 2571 points
Part Number: PCM5101A
Other Parts Discussed in Thread: NE5532A

Hey Team, 

Have a few questions for you

  1. It states that the minimum load is 1K. and typical output voltage is 2.1V.  So, it can drive only 2.1mA in 1K load or generate 4.41mW audio power at 1K. Am I understanding that correctly?
  2. Since my application requires 80 mW at 600 ohm, does it mean I need an audio amp? Any suggestion?
  3. Looks like the development board has the same schematic as in Fig 33 of DS. What is the purpose of 470 ohm in parallel with 2.2nF or 2200pF  is limit the  BW to about 1MHz?
  4. Why is there 100K pulldowns on I2S bus in development board?
  5. If we tie OUTL and OUTR nets past the 470 ohm resistors together, will that double output load current to 4.2 mA?

Thanks!

Cameron

  • +1
    TI__Mastermind 23460 points

    Hi Cameron,

    If you need to drive an impedance lower than 1K you should consider a buffer that is capable of driving it with your targeted power ( for that you need to post a separate thread with amplifier question so it goes to the appropriate group to suggest the best possible amp, we use NE5532A pr OP1612 , OPA2351 for some other dacs ). The 470 Ohm along with the cap is acting as passive  LP filter. We are using pull down resistors on all digital pins to pull them to GND when signals are not present, if you want  to connect then directly to Processor you should be ok without PD. This is a stereo voltage DAC ( not differential DAC or current DAC)  and shorting the two channels can only  improve the dynamic range by reducing noise floor but your Vout is not gonna change.

    Regards,

    Arash

  • 0 in reply to Arash Loloee
    TI__Intellectual 2571 points

    Thank you Arash!

    Are there any Audio DACs that can drive >11mA output?

    Thanks,

    Cameron 

  • 0 in reply to Cameron Wutzke
    TI__Mastermind 23460 points

    You're welcome.

    you can check out TLV320DAC310x family, (DAC3100 is 2.5W into 4 Ohm or 1.6W into 8Ohm).