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TPS2549: TPS2549 CDP Communication issue

Yang Wu
Expert 3320 points
Part Number: TPS2549

Hi Team,

My customer has an issue about TPS2549 communication. The sch is shown as below. When it's set at CDP mode (CTRL1 = CTRL2 = CTRL3 = High), it cannot communicate with the controller (PC). but when the resistor UR57 is removed, it can communicate normally.

The first waveform is with UR57, the second is without UR57. Blue line is the CTLR3, yellow line is CTRL1 & CTRL2.

So, how to explain this phenomenon? 

thanks!

Yang

  • 0
    TI__Mastermind 30000 points
    Hello Yang,

    Would you mind elaborating on what you mean by "cannot communicate with the controller (PC)"? Is the TPS2549 not detecting when a device is connected to the Type-A port? I'm not sure that I understand what exactly is the problem here
  • 0 in reply to Adam Mc Gaffin
    TI__Expert 3320 points
    Hi Adam,

    It's not connection problem, it's that PC or portable device can't launch the handshaking process with TPS2549. but when UR57 is removed (shorted), handshaking process works. So, what do you think?

    Thanks,
    Yang
  • 0 in reply to Yang Wu
    TI__Mastermind 30000 points
    Hello Yang,

    If the connected portable device cannot begin the enumeration process, my initial thought is that the D+ or D- lines are pulled low on the system. Nothing on our part would do this so it seems like something on their board is pulling this line low. May want to check there. If not, see if the customer can leave UR57 removed