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TPS25751: TPS25751S PDO configuration and SOP′ (E-Marker) communication

Conor
Guru 12490 points
Part Number: TPS25751


Hi,

I am evaluating the TPS25751S in a USB PD application and would like to confirm its behavior regarding cable (E-Marker) communication.

In our setup, we configured the PDO table to provide only 5 V / 3 A. In this case, we do not observe any SOP′ (Cable/E-Marker Discover Identity) messages on the PD analyzer. My understanding is that when higher PDOs such as 9/12/15/20 V or 5 A are advertised, the source is required to communicate with the E-Marker cable using SOP′ messages.

Could you please confirm the following points?

  1. Is it expected behavior that TPS25751S does not initiate SOP′ communication when the PDO is limited to 5 V / 3 A only?

  2. Can we assume that this behavior is compliant with the USB PD specification rule that E-Marker communication is not mandatory when the PDO current does not exceed 3 A?

Best regards,

Conor

  • 0
    TI__Intellectual 1720 points

    Hello Conor,

    Thank you for reaching out. Please give me till the end of the day Monday to respond back.

    Thank you,

    Katilynn

  • 0 in reply to Katilynn Mar
    TI__Intellectual 1720 points

    Hello Conor,

    Thank you for your patience. 

    Conor said:
    Is it expected behavior that TPS25751S does not initiate SOP′ communication when the PDO is limited to 5 V / 3 A only?

    Your understanding is correct, SOP' communication is not observed for a 5V/3A PDO.

    Conor said:
    Can we assume that this behavior is compliant with the USB PD specification rule that E-Marker communication is not mandatory when the PDO current does not exceed 3 A?

    Yes this behavior is compliant with the PDO current being under 3A.

     Thank you,

    Katilynn