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TPS65987D: Transmit Sink Capabilities definition to fit sink power requirements

Philippe VILLET
Prodigy 30 points
Part Number: TPS65987D
Other Parts Discussed in Thread: TPS65987

Hi, 

I'm using the TPS65987DDH in SOURCE and SINK mode.

  • I'm able to configure one transmit source capability : 5V, 0.9A (Using PP2 switch). It's Ok and works correclty. 
  • For the SINK mode, i would like to identify with the GPIOs if the attached source can provide a power higher than 27V
    • To achieve this goal, I've tried to setup 5 Sink PDO (All "Fixed Sink" with "Ask for Max" selected) - PDOs 2 to 5 are defined to require 27W as a minimum power (Voltage x Minimum Operating Current)
      • PDO 1: Voltage 5V, Operating Current 0.9A, Maximum Operating Current 3A, Minimum Operating Current 0.9A.
      • PDO 2: Voltage 9V, Operating Current 3A, Maximum Operating Current 3A, Minimum Operating Current  3A.
      • PDO 3: Voltage 12V, Operating Current 2.25A, Maximum Operating Current 3A, Minimum Operating Current 2.25A.
      • PDO 4: Voltage 15V, Operating Current 1.8A, Maximum Operating Current 3A, Minimum Operating Current 1.8A.
      • PDO 5: Voltage 20V, Operating Current 1.35A, Maximum Operating Current 3A, Minimum Operating Current 1.35A.
  • My understanding is that the USBC SOURCE provide the list of the PDOs it can provide and the SINK (My TPS65987) requests the appropriate index in the list of PDO's provided by the SOURCE based on the PDO's I've defined. 
    • For example,  If I plug the a USC-PD power supply with the following characteristics: (SOURCE PDOs): 
      • 5V-3A
      • 9V-2A
      • 12V - 1.5A
      • 15V - 1.2A
    • The only fitting PDO on my SINK side is 5V - 3A, any other are not matching between SINK and SOURCE. 
    • Unfortunately, I observed the TPS65987 is asking for SOURCE PDOs N°4 => 15V 1.2A and report also the GPIOs (configured as "Port 0 Sink PDO Negotiated TTx") as SINK PDOs negotiated as 4. VBUS is measured at 15V.
    • Is there a way to configure SINK PDOs and GPIOs to easily identify is the negotiated power is higher or lower than 27W ? 

Below are some screenshot from the PD protocol analyzer showing the handshake: 

Thanks for your support

Philippe

Source capabilities expose by the SRC:

Request from the SNK(My TPS65987DDH):

  • 0
    TI__Mastermind 34306 points

    Hi Phillipe,

    Philippe VILLET said:
    My understanding is that the USBC SOURCE provide the list of the PDOs it can provide and the SINK (My TPS65987) requests the appropriate index in the list of PDO's provided by the SOURCE based on the PDO's I've defined. 

    Yes, that is correct. "Ask for Max" in the transmit sink capabilities does not mean that we will only request a sink contract if the source offers the full power. 

    TPS65987 GPIOs are limited to the events advertised in the TRM.

    We have an event that will trigger if you are sinking a voltage greater than a defined threshold that may work in your case. You can set the voltage threshold in the Port Configuration register.

    Thanks and Regards,

    Raymond Lin