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TPS2543: charging modes clarification

Aaron Spaete
Expert 4310 points
Part Number: TPS2543

Team,

My cusotmer has the following question regarding the use of TPS2543:  

If I have the USP port high charging at 2.4A (CDP mode, ctrl123 = 111, ILIM_sel = 1) and the suddenly switch it to SDP mode by changing ILIM_SEL from 1 to 0, will it try to negotiation with the USB device again to bring the charging current to low limit.  I’m testing it with dumb resistor load, and instead of going from 5V-2.4A to 5V-1A, it goes to 0V-0.5A.  I think the dummy resistor tries to load 2.4A so overload condition occurs and the chip brings down the voltage.  I think if the load is the actual device, it may re-negotiate to bring the current down to 1A to avoid overloading, then it would work fine.  Can you confirm if I’m on the right track?

Regards,

Aaron

  • 0
    TI__Mastermind 27380 points
    Aaron,

    If you switch between CDP (1111) and SDP (1110) there should be no discharge, so there is not a required loss of VBUS. However, if you have a 2.4A load and switch to a 1A current limit, you will force the device into current limit and might brownout the downstream device or cause the TPS2543 to go into thermal protection. This is likely what you are seeing.

    If you change the load to 1A, you should not see any discharge.

    You are exactly on the right track.

    Please click the customer thinks resolved if I have fully answered your question, or ask me any further questions and I will be happy to help.
    Regards,
    Chuck
  • 0 in reply to Chuck Branch
    TI__Mastermind 27380 points
    Aaron,

    I have not received any updates on this thread in nearly a week, so I will move it to the TI Thinks Resolved category now.

    If you have further questions, please feel free to respond to the thread and I will answer them, if not please click the customer thinks resolved button on this message.

    Regards
    Chuck