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Is PD Controller needed on both Host(DFP) and Client(UFP) side?

ARUN K S
Prodigy 40 points
Other Parts Discussed in Thread: TPS65981EVM

Hi ti-USB-c Support,

My usecase:

Client side(sink) needs to draw power from USB-C and there is no any external power to client i.e fixed role no Dual role.

Query:-

To request for 12V/3A power from source what all steps(F/W-TPS65986E) changes one has to considered from client and host side to prepare for power contract negoiation or its just matter of power configuration table modification. If so table has to be updated on which side? 

How to create PDOs/RDOs on either side by which i can start getting 12V instead of default 5V.

Thank you, 

  • 0
    TI__Genius 10370 points

    Hi Arun,

    Welcome to e2e! This is a good question. A PD controller is needed on both sides for voltages greater than 5V. In the current USB-PD spec (PD2.0 & PD3.0), the voltages that can be offered are 5V @ 3A, 9V @ 3A, 15V @ 3A, and 20V @ 5A.  For any voltages outside of these four, the system will NOT be USB-PD compliant.

    The PD controller creates a PDO from a GPIO pin. This PDO is a high/low signal that's used to turn on and off different voltages during a PD contract. You can map out the GPIO events through the GUI (Applications Customization Tool).

    My recommendation is to use the TPS65981EVM board because it can source all four voltage rails (5V, 9V, 15V, 20V) and it comes with an FTDI board for easiness of flashing the PD controller.

    One last thing, we have several great resources on our PD controllers. Feel free to check them out here: http://www.ti.com/product/TPS65981/technicaldocuments

    I hope this helps and If this answers your question, PLEASE select  This resolved my issue 

  • 0 in reply to Aramis P. Alvarez
    Prodigy 40 points

    Hi,

    Its well put across thank you, till now i assumed Voltage range can be any like 12V/14.4V but, as you mentioned its always std rating.(5,9,15,20) has to be adopted. Still one can opt for non USB-PD compliant right? So, what is your recommendation  i.e stick on to standard and use power railing logic tp step down the rating as required, or use non USB-PD rating.

    About PDO , which side of USB-C has to maintain configuration table to showcase/request for voltage range like for eg: source support 5,9,15,20 

      Thank you,

  • 0 in reply to ARUN K S
    TI__Genius 10370 points

    Hi Arun,

    You are correct. One can create any voltage they would like, but if it's not a 5V, 9V, 15V, or 20V rail then sink PD controller won't' be able to ask for the voltage that's non-compliant.

    We always recommend going with the USB-PD specs per usb.org. For the PDO question, the SOURCE  side will have the PDO's set high/low depending on the PD contract (a DRP device would need this as well). This is usually done by having a variable DC/DC controller and changing the Feedback Resistor to the voltage needed. You can also have multiple Buck and/or Boost devices and enabling each one for the voltage needed.

    If you need a schematic for reference, feel free to take a look at the TPS65981EVM user's guide. This will show how we designed the variable DC/DC controller with PDO's from our PD controller.

    I hope this helps and If this answers your question, PLEASE select  This resolved my issue