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TPS65987DDJ: setting of source cap extended data block

Sai Loo
Expert 5110 points

Part Number: TPS65987DDJ

Hi team,

For PD2, or with PD3 but do not want to use the source cap extended data block, we could set the peak current at the "Source capability" bit 21:20, and set the "source cap extended' peak current field to 00b. Other than not using the features in the "source cap extended register", is there any other drawback with this setting (especially on the backward compatibiltiy, or it is better in this case)?

Will set the peak current in "source capability" to 11, it will not read teh "source cap extended block? or it depends on the 0x42 register (PD 3 Configuration register)?

SK Loo

  • 0
    TI__Expert 4455 points

    Hi SK,

    A partial answer is that source cap extended messages are only supported (and sent) if the item is checked in the PD3 configuration register.

    For sure this is also only supported between port partners that both identify as supporting PD rev 3.

    Is there a particular use case that you have concern about?

    Regards,

    Scott

  • 0 in reply to Scott T
    TI__Expert 5110 points

    Hi Scott,

    The use case will be, this is a monitor application and will set it to PD3, making use of the additional features in the extended data block. In this case, need to set the peak current to 100% in "source cap" register.

    This is not an issue if the host (notebook) connected is a PD3, but if the host is PD2, it will only received 100% peak current capability, whereas the source is actually capable of 200% peak current.

    If wanted to have 200% peak current in both PD2 and PD3, then could not use "extended data block".

    Regards,

    SK Loo

  • 0 in reply to Sai Loo
    TI__Expert 4455 points

    Hi SK,

    I think you are correct. The Source Cap Extended Data Block allows a source to supply additional information in response to a  Get_Source_Cap_Extended message. If the PD3 is not supported or the port partner does not issue the Get_Source_Cap_Extended request then it cannot benefit from the additional information.

    Regards,

    Scott