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Problems with PCM2706/7

PeterS
Prodigy 50 points
Other Parts Discussed in Thread: PCM2706

We are having continued issues with a prototype design using these parts.  

 

The first issue seems to be resolved by connecting pin 3 (Host) to 3V3 vs ground as stipulated in the data sheet

http://focus.ti.com/lit/ds/symlink/pcm2706.pdf   (page 29)

more so wanting to bring this to your attention

 

The second issue that has not been resolved yet is that the right analog channel does not work on multiple boards (every one that has Host tied high- the rest dont work at all)

are there any known issues/ causes for this?  It does output the 1.65 DC bias correctly

 

Thank you,

Peter

 

 

  • 0
    TI__Guru 64206 points

    Is the device self-powered or host-powered? Do you use custom descriptors?

    Is it possible to get an excerpt of your schematics that show how the PCM2706 is hooked up to the USB bus & the power supply?

    There are no know issues w.r.t. right analog channel problems.

  • 0 in reply to Dominik Hartl11
    Prodigy 50 points

    Than you for the reply. 

    aipapps said:

    Is the device self-powered or host-powered? Do you use custom descriptors?

    it is bus powered. No custom descriptors yet.

    aipapps said:

    Is it possible to get an excerpt of your schematics that show how the PCM2706 is hooked up to the USB bus & the power supply?

    There are no know issues w.r.t. right analog channel problems.

    http://www.2shared.com/file/5784185/62b6e81e/PCM2706_schematic.html

    It is laid out per pg.29 on data sheet.  The rest of the board is not populated so there is no unexpected behavior on the function pins. 

    Clock powers on consistently.

     

     

     

  • 0 in reply to PeterS
    Prodigy 50 points

    Also, pulling pin 3 high (500mA mode) did not provide a viable solution after all.  Next day all four boards did not work and are now intermitently recognized. 

     

    If there are no known issues it must be a layout issue or clock issue I would imagine.  Any recomendations?

     

    Thank you

  • 0 in reply to PeterS
    Prodigy 50 points

    Here is some more info on the issues we are having...

    This is a screen capture from SnoopyPro, a USB bus sniffer. Note the two packets at the end. The error says

    No Configuration Present => unconfigure device!


    This happens after successful configuration and about 200 successful isochronous transfers. Sometimes, the successful isochronous transfers do not occur and the error message appears immediately following an apparently successful configuration.

    http://www.2shared.com/file/5784437/69879212/pcm2707error.html

  • 0 in reply to PeterS
    TI__Guru 64206 points

    In your schematics, the net labeled "3V3" is not driven by an external regulator, correct? (it must not be driven. No other pins besides the ones from the PCM2706 that your schematics show must be connected to that net).

    The 10uF capacitor (C26) on the VBUS line can cause problems (but won't explain the errors reported by USB bus sniffer). Can you try to remove this capacitor, please?

    The schematics you provided look correct.

  • 0 in reply to Dominik Hartl11
    Prodigy 50 points

    There is no external regulator. 

    It seems we have resolved the issue by using a different oscillator circuit .  We will probably respin the prototypes with clock ICs though.