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PCM1862: Inquiry about the XO, XI (9, 10) pin and GND connection.

downey KIM
Intellectual 600 points
Part Number: PCM1862

Hi TI team.

We started the new project for AI speaker. PCM1862 is used in the project. the project was NG at ESD test.

ESD test standard - contact : +-4kV, Air : +-8kV.

Symptom : not operating BCLK, LRCK and DOUT of PCM1862.

The hardware design referenced datasheet.

MCLK is a slave. therefore pin9 & pin10 is open(floating).

But ESD test is OK after pin9 & pin10 connected GND. is it no problem that PCM1862 is operating? 

Please check my questions.

Thanks & Regards.

  • 0
    TI__Guru 62085 points

    Hello,

    The PCM1862 ESD ratings are featured in Section 7.2 of the product datasheet and the ratings are +/-2kV HBM and +/-750V CDM which are below the levels you're testing at.  Are you implementing any additional ESD protection to prevent the large transients you're applying from reaching the PCM186x?

    Also, where and how are you applying the ESD pulses?  Is this through a veritical/horizontal coupling plane or are you directly touching the connectors on your design, pins on the IC?

  • 0 in reply to Collin Wells
    Intellectual 600 points
    Hi Collin,
    I know the PCM1862 ESD ratings. we didn't shoot directly the PCM1862 PIN and PCB. the ESD test did shoot a case of product.
    I just ask to you that can PIN9, 10 of PCM1862 be connected to GND?
    According to the datasheet, PIN10 can be connected to GND. let me know if PIN9 can be connected to GND.

    Thanks
  • 0 in reply to downey KIM
    TI__Guru 62085 points
    Thanks for the information. We've seen similar effects with floating pins on vertical/horizontal plane coupling testing which is similar to zapping the case as you're describing.

    Pin 9 is a digital output and we don't recommend connecting it straight to GND. Since most of these internal crystal driver circuits are inverter based, with XI GNDed XO may be driving to +3.3V. Can you probe the XO output and confirm? If it's driving to +3.3V then I'd suggest connecting it to DVDD through a 1kOhm pull-up. If it's driving to GND then try a 1kOhm pull-down to GND and see if you're still able to pass the testing.
  • 0 in reply to Collin Wells
    Intellectual 600 points
    Hi Collin,
    Thanks for your support.
    I checked your comment. PIN9 is a output about 1V. In this case, which of the following must be pull up or pull down?

    Regards.
  • 0 in reply to downey KIM
    TI__Guru 62085 points

    Hello,

    Thank you for making the measurements.  Based on the current output voltage we recommend the 1kOhm pull-down to GND.