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TPS65994AD: How to Send a Message via TPS65994AD to other PD Controller for System Power State Notification?

Huang Jack
Prodigy 70 points
Part Number: TPS65994AD

Tool/software:

I have a mature project using the TPS65994AD on an ADL-P platform, where power is supplied via a Type-C port connected to a customer's daughter card to draw 20V. Now, the customer has proposed a functional requirement, and I’d like advice on how to implement it. The requirement is as follows:

When the system is powered off, the TPS65994AD should send a message to the partner PD controller (model EJ899I) via the CC pin. Upon receiving a message indicating the system is powered on, the EJ899I will assert a GPO signal.

Questions:

  1. How can I send this message through the CC pin using the TPS65994AD (or through other pin in TYPE-C) ?

  2. What would be an appropriate message/content to send for this purpose?

Additional Info:

  • The customer’s sub-card’s Type-C port is exclusively connected to my motherboard.

  • The goal is to notify the EJ899I of the system's power state (off/on) via PD communication.

Any guidance on register configurations, PD messaging protocols, or relevant examples would be greatly appreciated!

  • 0
    TI__Genius 12735 points

    Hi Jack,

    This can be accomplished through sending a PD alert message to the connected port partner through CC pins.

    The PD alert message is defined by USB-IF PD spec. There are several types of alert messages. Customer can use the "Operating Condition Change" alert type defined below in the spec.

    To configure the alert message in the TPS65994AD, you will need to modify the 0x75 TX_ADO register to change the TypeOfAlert field, Bits 31:24, to "Operating Condition Change", a value of 0x10. The other fields can remain 0. Definition of the 0x75 TX Alert Data Object register is below, also found in TRM. This change to the PD configuration can be done in the GUI.

    Then, before the system goes to power off state, the EC or MCU will need to write the 'ALRT' command to the TPS65994AD over I2C. This command will prompt the PD to send a PD alert message to the connected port partner, with Operating Condition Change type. The port partner will receive the message and handle it on their side.

    Attaching TPS65994AD TRM. Let me know if you have questions.

    4087.TPS6599xAD_TRM_slvubt3.pdf

    Best,

    Alex