• State Resolved
  • Locked Locked
  • Replies 2 replies
  • Subscribers 31 subscribers
  • Views 81 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

PCM2906C: PCM2900 evaluation board design

Michael Bailey
Prodigy 10 points

Part Number: PCM2906C
Other Parts Discussed in Thread: HID2

I'm using the evaluation board (SBAU-195) as a patern for designing a USB audio interface.

Why are HID0, HID1, HID2 pulled up to logic high when internally they are pulled to ground? Why not pull them to ground, or better yet, connect them to ground?

Why are the L+R audio inputs and L+R audio outputs capacitively coupled? The op-amps associated are referenced to "VCOM", a psuedo-ground. There is no voltage across capacitors C108, C109, C101, C102.

Why use an electrolytic capacitor for audio coupling? In time, the electrolytic capacitor fails due to lack of proper bias.

 

  • 0
    TI__Guru 51030 points

    Hi Michael,

    The HID input pins are active high. You have to pull them up in order to trigger the HID interrupt (pause, play, volume up/down, etc).

    I agree with you those caps seem redundant. It might be for the filter design consideration, but they are not required for the codec outputs/inputs.

    Since the caps are handling AC signals only the lifetime of the cap should be fine.

    Best regards,
    Jeff McPherson

  • 0 in reply to Jeff McPherson
    Prodigy 10 points

    Thankyou.

    I will tie the HID inputs to ground. I'm not using HID at all.

    I will also eliminate the redundant coupling capacitors.