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GD75232: GD75232 output signal issue when power ON

user3830479
Expert 1090 points
Part Number: GD75232
Other Parts Discussed in Thread: GD65232

Dear all:

     My customer use GD75232 of their RS232 port ,they feedback an issue. attached is circuit.

     Power sequency follow  VDD-VSS-VCC-VIO(-12V to 12V  to 5V）,  when +12 power on, Output PIN have a pulse  up to 3V, and then down to

    -12V(normal voltage)  before signal input. we have a  doubt that is it  normal for this IC?  How can we  eliminate the pulse?  please help to check,

    

  • 0
    TI__Mastermind 25705 points

    Thanks for using our device. The power sequence of GD75232 should be: (quote from datasheet) 

    When powering up the GD65232 and GD75232, the following sequence should be used:

    1. VSS

    2. VDD

    3. VCC

    4. I/Os

    What's the state of input after power on, is it biased for floating? You can refer to the waveform of this post (e2e.ti.com/.../2248651) for previous discussion about the device. Please let me know if you have any questions, please let me know.

    Regards,

    Hao

  • 0 in reply to Hao L
    Expert 1090 points
    Yes , I following the sequence, when VDD +12 supply, Output PIN have a pulse up to 3V(not signal input), it is generated by GD75232? is it normal for this IC?
  • 0 in reply to user3830479
    TI__Mastermind 25705 points

    Can you please upload the waveform? Or if you can confirm they look like this one, they may be normal. Thanks!