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TPS65982: Discharge circuit

Takashi Onawa
Genius 13200 points

Part Number: TPS65982

Hi Team,

What are the conditions under which the discharge circuit of TPS 65982 is activated?

Especially, My customer wants to know if it also works in the case all PDOs use the same path, like variable DCDC architecture.

Regards,

Takashi Onawa

  • 0
    TI__Mastermind 36756 points
    Hi Onawa-san,

    The VBUS Discharge circuit is used whenever the VBUS port goes from a connected to a disconnected state. This would also be used to discharge VBUS to 0V during a power role swap on the TPS65982.

    Thank you,
    Eric
  • 0 in reply to Eric Beljaars
    TI__Genius 13200 points

    Hi Eric-san,

    As I mentioned first, My customer choose  variable DCDC architecture and power path is never switched and disconnected in normal operation.

    In this case, My customer want to know whether the discharge circuit also works in stepping down PDO change case or not.

    Regards,

    Takashi Onawa

  • 0 in reply to Takashi Onawa
    TI__Mastermind 36756 points
    Hi Onawa-san,

    Is this application only using the PP_EXT path to source all of the voltages? If that is the case, the VBUS Discharge circuit will not be used. The only scenario where the VBUS Discharge circuit is used when sourcing is when you swap from PP_HV or PP_EXT to PP_5V.

    Thank you,
    Eric
  • 0 in reply to Eric Beljaars
    TI__Genius 13200 points
    Hi Eric-san,

    Yes, do you think it is necessary to put external discharge circuit on VBUS in this case?

    Also, How abaout VBUS Transition to VSAFE0V?
    Does the discharge circuit also work in this case using PP_HV?

    Regards,
    Takashi Onawa
  • 0 in reply to Takashi Onawa
    TI__Mastermind 36756 points
    Hi Onawa-san,

    When returning to VSAFE0V, the TPS65982 will use the internal VBUS Discharge circuit. This is also the case during a power role swap when VBUS returns to VSAFE0V before swapping.
    The VBUS Discharge circuit will work if you swap from PP_EXT to PP_HV. However, if all of your PDOs are on PP_HV then the VBUS Discharge will not engage. The VBUS Discharge will only engage if you are changing power paths during operation.
    Most DC/DCs can adjust their voltage within the PD timing spec. If the Customer is using a variable DC/DC that can adjust it voltage quick enough then an external discharge is not needed. This is most likely the case but it would be good to test.

    Thank you,
    Eric
  • 0 in reply to Eric Beljaars
    TI__Genius 13200 points
    Hi Eric-san,

    OK, I understood.

    Regards,
    Takashi Onawa