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TPS26750: When is POWER_PATH_EN asserted?

Nathan Langford
Prodigy 70 points
Part Number: TPS26750
Other Parts Discussed in Thread: BQ25756,

Tool/software:

When is POWER_PATH_EN asserted or not asserted? I might be overlooking it but I can't seem to tell from the datasheet.

I'm assuming it is asserted according to the Dead Battery Configuration in Table 7-6 before a configuration is loaded, then asserted after a PD contract is negotiated that meets the required sink PDOs, also taking into account the "Auto Disable Sink Upon Capability Mismatch" configuration bit. What else effects when the sink path is enabled? Liquid detection?

  • 0
    TI__Mastermind 34126 points

    Hi Nathan, 

    The POWER_PATH_EN pin is used to enable/disable the external high voltage power path (5V - 48V) in both source and sink mode. Here are some example schematics/block diagram on POWER_PATH_EN implementation:

    Let us know if you have any further questions or concerns! 

    Thanks and Regards,

    Raymond Lin

  • 0 in reply to Raymond Lin
    Prodigy 70 points

    Hi Raymond,

    Thank you for your reply. I understand the purpose of the POWER_PATH_EN pin, but I can't find information on the criteria that cause it to be enabled.

    A few specific questions that this information would answer, for example:

    • Will the sink path be enabled as soon as an implicit 5V contract is formed using the Rd resistors on the CC pins, or only after completing PD negotiation with the PD supply?
    • If BC1.2 support is implemented, will that enable the sink path if any BC1.2 charger is detected or only if the BC1.2 charger meets certain criteria such as current capability? If I connect a 5V 1A BC1.2 charger, will that cause the sink path to be enabled?
    • What fault conditions will cause the sink path to be disabled? Over-voltage? Reverse current? Liquid detection?

    As an example of what I'm looking for, the BQ25756 datasheet includes this list:

    A new charge cycle starts when the following conditions are valid:

    • VAC is within the ACUV and ACOV operating window
    • Device is not in HIZ mode (EN_HIZ = 0 and ILIM_HIZ pin voltage is below VIH_ILIM_HIZ)
    • REGN is above VREGN_OK
    • Battery charging is enabled (EN_CHG = 1 and CE pin is LOW )
    • No thermistor fault on TS
    • No safety timer fault


    I'm hoping there exists a similar list of conditions for the TPS26750, specifying when POWER_PATH_EN is asserted and the sink/source path is enabled.

    Thanks,

    Nathan Langford

  • 0 in reply to Nathan Langford
    TI__Mastermind 34126 points

    Hi Nathan, 

    Nathan Langford said:
    Will the sink path be enabled as soon as an implicit 5V contract is formed using the Rd resistors on the CC pins, or only after completing PD negotiation with the PD supply?

    TPS26750 enables the sink upon an implicit 5V contract when in APP mode (valid PD config is loaded and running). However in dead battery mode (PD first boots up from VBUS), if the ADCIN1/2 settings are configured for SafeMode and no valid PD config is loaded into TPS26750 yet (PTCH mode), TPS26750 will not enable the sink path until a valid PD config is loaded. 

    Nathan Langford said:
    If BC1.2 support is implemented, will that enable the sink path if any BC1.2 charger is detected or only if the BC1.2 charger meets certain criteria such as current capability? If I connect a 5V 1A BC1.2 charger, will that cause the sink path to be enabled?

    TPS26750 will enable its sink path for legacy BC1.2 charger. There are no minimum power requirement for legacy devices. For PD capable devices, you can configure in Autonegotiate Sink what power level to enable the sink path (Auto Disable Path upon Capability Mismatch). 

    Nathan Langford said:
    What fault conditions will cause the sink path to be disabled? Over-voltage? Reverse current? Liquid detection?

    All of these fault conditions you listed out can cause the sink path to be disabled when the PD detects it. Several other reasons why the sink path will be disabled:

    1. HardReset PD message was sent/received 

    2. Cable detach was detected (either cable was physically removed or something else that forced a disconnection) 

    3. TPS26750 has capability mismatch enabled and sink path disables when the source is unable to provide the minimum power requirement 

    4. During power role swap, the sink path will temporarily disable to transition the BQ from source->sink or sink->source mode

    Let us know if you have any further questions or concerns! 

    Thanks and Regards,

    Raymond Lin

  • 0 in reply to Raymond Lin
    Prodigy 70 points

    Thank you, Raymond.

    How would a BC1.2 implementation work when using the TPS26750 to control a BQ25756 battery charger? Will the TPS26750 set the appropriate input current limit on the BQ25756 automatically?

  • +1 in reply to Nathan Langford
    TI__Mastermind 34126 points

    Hi Nathan, 

    TPS26750 reports the type of BC1.2 connection made in Power Status register 0x3F. In current implementation TPS26750 doesn't automatically configure BQ25756 INDPM based on BC1.2 detection. TPS26750 only configures the BQ INDPM based on the Type-C and PD current (when applicable).

    Let us know if you have any further questions or concerns! 

    Thanks and Regards,

    Raymond Lin