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TPS2549: CDP mode fails when device is turned off

Naser S.
Genius 11605 points
Part Number: TPS2549


Hi Team:

Customer is using the TPS2549 for a USB connection to charging his device.
His device draws more than 500mA, therefore the standard USB connection does not deliver enough power. This is why he wants to use TPS2549 in CDP mode.

When the device is turned on, the battery-charging v1.2 negotiation for CDP-mode between the device and the TPS2549 is successful and the device charges with more than 500mA.
When the device is turned off, the CDP negotiation fails and the device is only charged with a max of 500mA.

How can he gets the negotiation to work with a turned off device?
His device has a configuration and turns on when USB power is attached and turns off, when the USB power is removed. Reconnecting the device when it’s running is therefore not an option.

Thank you for your answer.

  • 0
    TI__Mastermind 32611 points
    Hello Naser,

    I just want to make sure that I am answering the right question. Which device is turned off?

    If the device that is turned off is the device that is being connected to the TPS2549, and it does not properly negotiate the BC 1.2 contract, then the TPS2549 will remain an SDP. This is what I suspect is happening, but I will need some scope captures to confirm.

    Is it possible for you to get me scope captures of the D+, D-, and VBUS lines of the device when it is connected and turned off so I can help debug what is going wrong?

    Regards,
    Chuck
  • 0 in reply to Chuck Branch
    TI__Genius 11605 points
    Thanks Chuck. I discussed your reply further with customer. I will send you my summary and analysis along with attachments directly to your Outlook.
    Regards,
    Naser
  • 0 in reply to Naser S.
    TI__Mastermind 32611 points
    Naser,

    Please click the customer thinks resolved to close out this ticket and I will support off line.

    Regards,
    Chuck