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TPS65986: Getting higher power PDO than requested

JoFu10
Intellectual 2385 points

Part Number: TPS65986

Hi,

We've recently tested our device using an 87w charger from Apple.  For our sink capabilities, we are set to either 5v / 3A max, or 9v - 20v / 3A max.  But using the Apple charger, TPS65986 register 0x34 is reporting the active contract is 20v / 4.3A.  Dumping 0x34, it shows data of 'ae 41 06 00 80 00'.
 
Do you know why this is?  Shouldn't the TPS65986 be selecting a PDO within the limits we defined?
Thanks,
Josh

  • 0
    TI__Mastermind 36756 points
    Hi Josh,

    When the Sink is requesting less than what the Source has to offer, the Sink will still accept the PD contract as the Source can supply everything that the Sink is requesting. In the Request RDO message, you will see that the Sink will request 20V/3A as this is what the Sink PDO is set to. Since the source can supply everything that the sink is asking for, there is no issue. If the Sink is asking for more than what the Source can provide, the PD contract will also still be accepted. However, in the Request RDO you will then see that the Capabilities mismatch bit is set, since the Sink is asking for more power than the Source can provide.

    Thank you,
    Eric