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TPS65988: Downstream Source PDO modification, based on available power from UFP Sink port.

Part Number: TPS65988
Other Parts Discussed in Thread: TPS65982, TPS65987

Is there any documentation to outline how to implement downstream DFP Source PDO management or modification, based on available power from an upstream UFP Sink port negotiated PDO?   Clearly applications such as docking stations or hubs may require this capability, and it's possible, but is there anything in the policy engine of the TPS65988 that helps to manage this, or does it require full Host interaction to read the Active Sink PDO information, and then modify the Source Capabilities register with appropriate PDO's to advertise?  

  • Hi Eric S.,

    The TPS65988 will not support this behavior with its internal FW. An external MCU would be required to read back the negotiated contract on the VBUS1 port and change the source capabilities on the second port.

    The concepts from the TPS65982 FW User’s guide all apply to the TPS65987/88, we do not have a separate document.

    Below is a brief description of how this can be achieved with an external MCU:

    1. MCU receives Plug insert interrupt on VBUS1 port

    2. MCU receives Power Status Update interrupt on VBUS1 port

    3. MCU read back active PDO in register 0x34 (Active Contract PDO)

    4. MCU deciphers data and determines how much can be offered in source capabilities of other port

    5. MCU changes Source Capabilities register for the other port

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

    Thank you,
    Eric