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TPS65982 RDO capabiluity mismatch question

Sam Pan
Expert 3860 points
Other Parts Discussed in Thread: TPS65982

Hi Team,

Two questions here -  

  1. When TPS65982 as sink and none of the source PDO match sink PDO, how would TPS65982 send RDO?
  2. Following #1, it seem we still turn on sink path when capability mismatch, may I know why? From system design point of view customer would hope we turn sink path off if the source can not support system sink

 

Below my test with sink PDO 5V / 2.4A, 14.8V / 2.0A, 10.8V~20V / 1.2A, auto negoitate priority by voltage.(1.11 FW).

It looks like TPS65982 still request 20V1A with cap mismatch set high and turn on sink path. System charger would then see 20V in this case and start to sink current. Should be better to turn off sink path in such case 

Reply from Arun Menon:

Hi Sam,

 

The Sink can still ask a PDO from Source if the voltage given in the Source capabilities PDO matches one of its Sink PDO. Now since the Current given in the PDO doesn’t match the Sink sends a RDO request with the ‘Capabilities Mismatch’ bit set high. This is the behavior in Auto-negotiate Sink mode.

 

If you want to sink to not request any RDO, then the Sink can be operated in Sink intrusive mode. In this case the Source PDOs will be sent to EC by the PD controller and the EC can decide and let the Sink PD controller know which Source PDO should be requested.

 

Regards,

Arun

  • 0
    TI__Expert 3860 points
    Hi Arun,
    Is it possible to have TPS65982/982D turn off the sink path when none of the current given in the source PDO match in Auto-negotiate Sink mode?
    This seem make more sense for system design --> If the source can not meet the system requirement, PD should turn off the path in case system sink more current than the source's capability and causing OCP

    Yes customer might be able to use EC to decide and let the Sink PD controller know which Source PDO should be requested, but there's also deadbattery condition that the EC is not powered before PD sink path turned on.
    In deadbattery condition if system needs 2A to power up but source only 1A, only TPS65982 can judge and decide if path should be on or off

    Thanks

    Regards,
    Sam
  • 0 in reply to Sam Pan
    TI__Expert 6505 points

    Hi Sam,

    Can you set the peak current capacity for each Sink PDO to  100%? Then OCP should be hit when 3A contract is established  and more than 1A is drawn by the sink. 

    Note: even though a 3A contract is established the sink may not be drawing 3A current. Is there is no load attached to sink the current drawn should be very less(<1A). Only when the current drawn by sink goes above 1A the OCP will be hit.

    Regards,

    Arun