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Original question:

TPS65981: TPS65981 5V to PP_HV and PP_5V0 both necessary?

TPS65981: TPS65981 5V to PP_HV and PP_5V0 both necessary?

Mario Michel95
Prodigy 160 points
Part Number: TPS65981

Hello TI Team,

our TPS65981 system will source power up to 20V/5A and works as a UFP (FullSpeed) only.

 I learned that it isn't necessary to provide PP_HV and PP_5V0 both as long as PP_Cable is supplied. But is it possible to disable both switches? We just want to negotiate 20V (PP_EXT) and just want to supply PP_EXT (20V/5A) and PP_Cable (5V/500mA). By disabling both switches I couldn't get any PD contract running, I tried to provide just 5V to PP_HV and activated the PP_HV switch. Now the PD contract is working (charging 20V to my notebook). Do I need to supply voltage to PP_HV or PP_5V0 in any case? If so, how about the power requirements for PP_HV or PP_5V0 in this case (as the external FET will supply 20V up to 5A after negotiation).

 Thanks and Regards

Mario

  • 0
    TI__Mastermind 36756 points

    Hi Mario,

    PD Negotiation always starts with 5V on VBUS. There are two ways you can resolve this:

    1. Supply 5V to either PP_5V or PP_HV and enabled a 5V Source capability before entering a 20V contract.

    2. Initially supply 5V to PP_EXT and then ramp the voltage to 20V on PP_EXT after you have negotiated a 20V contract.

    The easier method of the 2 would be to supply 5V to PP_5V or PP_HV.

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

    Thank you,

    Eric

  • 0 in reply to Eric Beljaars
    Prodigy 160 points
    Hi Eric,

    thanks for the information. I can supply 5V to PP_5V but before switching to 20V the 5V will supply our sink device (also including another TPS65981) immediately. On the SINK device I disabled PP_5V and PP_HV but during negotiation the 5V are switched out to the internal VBUS. Is there any way to prevent this behavior or do I need to add a power switch transistor to switch on my SINK device electronics not before as soon the 20V are available?

    Thanks and Regards
    Mario
  • 0 in reply to Mario Michel95
    TI__Mastermind 36756 points
    Hi Mario,

    The SINK device can be completely powered from VBUS, this is known as Dead Battery Mode. You do not necessarily have to provide 5V to the Sink device, you can have it purely powered from VBUS if desired.

    Thank you,
    Eric