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TPS65986: Any current draw expected from VBUS, when configured as a Host and Battery VIN_3V3 is present?

Eric S
Expert 5660 points

Part Number: TPS65986

My customer is expecting no current draw when configured as a Data Host, VIN_3V3 is present, and an SDP is connected.  However, they seem to be seeing ~15 to 20mA draw, and can't understand it.  If VIN_3V3 is present, but VBUS is also present (and they do enable dead-battery support in their system)....   is there any expected current draw from VBUS, and where is that specified?   Thank you.

  • 0
    TI__Mastermind 36756 points

    Hi Eric S.,

    If the dead battery flag has been cleared and there is nothing on the other side of the power path consuming current, the current should be relatively low. You can always check the status of the CC lines and D+/D- lines as those would be used when an SDP charger is connected.

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

    Thank you,
    Eric

  • 0 in reply to Eric Beljaars
    TI__Expert 5660 points
    Eric, it's been found that the majority of current drawn in this situation is from leakage on the System side of PP_HV. The only way to cut that down as desired, is to disable PP_HV, "IF" and only if they detect an SDP plugged-in. Is there a way to configure this or even to use a runtime command to disable PP_HV switch WITHOUT resetting the device? Our understanding is that any changes to Sys Config register 0x28 (bits 26:27 in particular for PP_HV setting) will cause device RESET and restart detection. Is that true? Thank you.
  • 0 in reply to Eric S
    TI__Mastermind 36756 points

    Hi Eric S.,

    You are correct, if any of the registers controlling PP_HV are adjusted, the device would disconnect and restart the detection. However, you could configure PP_HV to "Sink wait for SRDY" In this use case, the PP_HV path would not close until the "SRDY" 4CC command is sent over I2C. You could write a condition where the SRDY command isn't sent if an SDP is detected.

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

    Thank you,
    Eric

  • 0 in reply to Eric Beljaars
    TI__Expert 5660 points

    Eric, I think this should be last follow-up question...  this is good recommendation, but how does the SRDY scheme work with dead batteries?  I know TPS65986 will enable PP_HV as a sink if dead-battery support is enabled, prior to loading app code, but what then happens if our app code configures PP_HV to only turn on until SRDY?  Will PP_HV just stay on, or will it turn on initially then turn off until we send an SRDY? 

    Thank you.

  • 0 in reply to Eric S
    TI__Mastermind 36756 points
    Hi Eric S.,

    That's a good point. When booting in dead battery mode, the TPS65986 will still close the PP_HV path based on the BUSPOWERZ config. There isn't really a way around this when booting in dead battery mode. PPHV would just stay on.

    Thank you,
    Eric