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TPS25751: DEAD BATTERY CONFIGURATION CLARIFICATION NEEDED

THOMAS WALTER
Prodigy 150 points
Part Number: TPS25751

Tool/software:

Hi,

I am using the TPS25751 in dead battery mode and I would like some clarifications about the 3 modes :

- AlwaysEnableSink:

It is stated that "The device always enables the sink path
regardless of the amount of current the attached source is
offering"

But then just after it:  'USB PD is disabled until configuration is loaded"

So it is unclear for me what is "USB PD" refering to, is it a current limit ? What about the AutoComputeSinkMinVoltage ?

- NegotiateHighVoltage:

"This option is not recommended for systems that can
boot from 5 V. This configuration is not valid to use with any
supported battery chargers"

Isn't the correct definition this one ?

"This option is not recommended for systems that can
only boot with a maximum voltage of 5V. This configuration is not valid to use with any
supported battery chargers"

  • 0
    TI__Guru 64791 points

    Hello,

    THOMAS WALTER said:
    "USB PD" refering to, is it a current limit ? What about the AutoComputeSinkMinVoltage ?

    This is referring to the power delivery (PD) state machine.   The USB type-C is still applied where the source presents an Rp based up the current capability and the TPS25751 provides the Rd to establish a connection.  The power path is enabled without regard to the current advertised by the Rp value.

    https://www.ti.com/lit/wp/slyy109b/slyy109b.pdf#page=4

    The autoComputeSinkMinVoltage is related to the explicit contracts negotiated in PD.

    THOMAS WALTER said:
    "This option is not recommended for systems that can
    boot from 5 V. This configuration is not valid to use with any
    supported battery charger

    In Negotiate High voltage the PD will negotiate to the highest PD voltage, up to 20V, and close the power path.  For example, ff the system boots from 5V (components down stream from the PPHV) but 20V is provided (instead of 5V) this could potentially damage the system.  The key here is that the power path is closed and the negotiated voltage is otherwise unknown to the system (because you are in a dead battery condition).  The voltage could be between 5 and 20V.

    Regards,

    Chris