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PCM2900C is damaged with the Vbus provided

user4325547
Prodigy 40 points
Other Parts Discussed in Thread: PCM2900C

Hello engineers,

The phenomena is that the PCM2900C is damaged after the 5V Vbus provided for over 1 minutes.

  1. The internal voltage is ok, I can measured 3.3V output from every LDOs.

  2. About 3.1V voltage on the XTI pins instead of the oscillation.

  3. The current requirement on the Vbus input is observed, 10ma in the initialization time, last more than 100mA.

  • 0
    TI__Guru** 110835 points

    Hi,

    Do you have a schematic you can share? Are you using an EVM?
    I think more than 100mA is too much for normal operation.
    Does this happened more than once?
    We need more information of your setup to give you better support.

    Best regards,
    Iván Salazar
    Texas Instruments

  • 0 in reply to Ivan Salazar
    Prodigy 40 points

    Hi Ivan,

    Thanks for your quick support!

    I think the poor soldering incurs this damage, I have resolved it . However, I have another find, please could you help me clarify it?

    Regarding the typical application in the figure 38 contained the PCM2900C datasheet, the SSPND pin, namely 28th pin, is connected to the LDOs output. Unfortunately, it's the output, so why it has to be connected to the internal LDOs directly?

    In the other hand, I have seen the  PCM2900C2902C2906CEVM-U user guild, this SSPND pin doesn't be connected to any power source.

    In the experiment, I observed the SSPND is low level if only providing the Vbus and floating the USB data line.

    I want to know should I connect SSPND pin to the internal LDOs directly or make it floating alone?

    BR,

    Weihua

  • 0 in reply to user4325547
    TI__Guru** 110835 points
    Hi Weihua,

    Sorry I can't see any connection from /SSPND to an internal LDO output; in Figure 38 this pin goes to the output stage as a Mute/Power Down signal and is also a voltage source for the HID controls but it isn't connected to any internal LDO.

    That's the normal /SSPND operation, when the device is powered but there is no data coming from USB it will go to suspend state and set low the /SSPND pin, if there is streaming data the pin will be set high.
    /SSPND pin could be used as a mute signal for subsequent stages, if this pin won't be used it could be left floating.

    Regards,
    Iván Salazar
    Texas Instruments
  • 0 in reply to Ivan Salazar
    Prodigy 40 points

    Sorry, it's my mistake. Indeed, it doesn't be connected to any power source.

    Thanks for the support!

    BR,

    Weihua