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TPS65981: Controlling Inrush

Jason Haedt
Expert 4630 points
Part Number: TPS65981

Hello TI,

I have a TPS65981 design that uses the 20V feature on the sink side.  I have a speaker setup Class D with big capacitors on the 20V bus and I am struggling to understand how to delay the overcurrent sense/disable/retry.  I've tried all the delays in the GUI for the device but that didn't work.  I thought I could manage this with the TPS65981 off the PP_EXT or PP_HV but have not been able to find a configuration that works.  I appreciate your thoughts,

-Jason 

  • 0
    TI__Mastermind 36756 points

    Hi Jason,

    When the TPS65981 closes the sink path, it will only soft-start for the 0V to 5V transition. It would not automatically soft start from the 5V to 20V transition as the FET is already fully biased at this point. It is expected that the system design can control the inrush current into the capacitors during the 5V to 20V transition.

    However, if you have an MCU in your system, you can configure the sink path to: "Configured for input, wait for SYS_RDY command" This will allow VBUS to negotiate up to 20V before closing the sink path. You would then have to send the SRDY 4CC command from the MCU to close the sink path. In this case, the TPS65981 would soft start from 0V to 20V. There are more details on this in the HI TRM.

    If this answers your question, PLEASE select This resolved my issue

    Thank you,
    Eric