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TPS65988: Configuring WAIT sent by TPS65988?

Chris Chen
Prodigy 10 points

Part Number: TPS65988

Hi!

In the interface manual for the TPS65986, the Control Configuration register allows for specification of the Intrusive mode, both as a source and as a sink. 

We're looking for a similar option on the TPS65988 - in our use case, the two ports have a dependency on each other, and negotiation can't be completed until information has been obtained by both devices. Is there another way to disable automatic negotiation, and send an automatic Wait to the sink while we wait for the configuration to complete? Similarly on the source side, is there any way to send SRDO?

Thanks!

  • 0
    TI__Mastermind 30000 points

    Hi Chris,

    I have a few clarifying questions for you.

    1. Do you have some external MCU on your system that can communicate with the TPS65988 via I2C? 
    2. And would you be able to give additional details on what information is needed on both ports? i.e is it power related or an alter mode such as DP or thunderbolt? 
  • 0 in reply to Adam Mc Gaffin
    Prodigy 10 points

    Hi! Thanks for following up - 

    1. Yes, there is an external MCU communicating with the TPS65988 via I2C
    2. The purpose of the ports is for power - no alternate mode needed. Essentially, the device is going to be used mainly as a power passthrough, drawing power from a source power supply, subtracting some to power itself, and then sending the rest through port 2. We need to coordinate the negotiation between port 1 and port 2 such that the correct PDO voltage and current values are advertised on port 2 and accepted before accepting a PDO from the source port 1. 

  • 0 in reply to Chris Chen
    TI__Mastermind 30000 points

    Hi Chris, 

    Thank you for the clarification.

    In register 0x27, you can configure the sink power paths to be enabled, but will wait until the SRDY command is received before closing that power path.

    The idea is that the TPS65988 will still negotiate a contract and sink current on VBUS, but will not close the power path to PPHV until the SRDY command has been received from the MCU. Once a device has been connected, the MCU can read register 0x34 which is the active contract negotiated at that time. From there, the MCU can make the decision on whether or not to close the power path by sending the SRDY command