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TPS25810: Dual type-c port application

Antony Lin
Genius 13480 points
Part Number: TPS25810


Hi,

The customer design is a dual-port type-c applciation using two TPS25810 chips.  They want to dynamically change the current capability based on the connecting status of the other type-c port, but they don't want to make use of LD_DET as descrined in datasheet (7.3.3.13 PPM Operation)

Their application criteria is to decrease the current limit from 3A to 1.5A whenever there's an UFP device connected at the other port.  Therefore, they plan to connect CHG_HI pin from UFP pin of the other TPS25810 chip.  Do you see any side effect or constraint here?

Thanks!

Antony

  • 0
    TI__Intellectual 1920 points
    Hi Antony,

    Is there any reason they prefer not to use the LD_DET pin?

    How much current is desired if just one port is connected vs. both connected to UFPs? If one port is connected 3A and if both are connected 1.5A each?

    Thanks,
    Donovan
  • 0 in reply to Donovan Porter
    TI__Genius 13480 points

    Hi Donovan,

    yes, they want to provide 3A when the connectino is valid only in one port, and provide 1.5A to both ports when connection is valid on both ports.

    LD_DET with threshold @ 1.95A (TYP) is too high for them.

    Antony

  • 0 in reply to Antony Lin
    TI__Intellectual 1920 points
    Hi Antony,

    Let me try this out with an EVM to verify. My concern is if port 1 is sourcing 3A and port 2 is then plugged into, port 1 will change to advertise 1.5 A but I'm not 100% sure port 1 will reconfigure to 1.5 A since it is already sourcing 3A. I believe it will but I would like to verify this first.

    Regards,
    Donovan
  • 0 in reply to Donovan Porter
    TI__Intellectual 1920 points
    Hi Antony,

    If port 1 is sourcing over 1.7A and a sink is connected to port 2, port 1 will limit the current to 1.7A and VBUS will fall below 5V, causing the sink to re-establish its connection. It will then reconnect at a max 1.5A. If this is ok with the customer than there shouldn't be any other issues.

    Regards,
    Donovan
  • 0 in reply to Donovan Porter
    TI__Genius 13480 points

    Hi Donovan,

    Regarding the reply you provided, is it applied to any case when we change current rating from 3A to 1.5A?

    Consdiering there's only one TPS25810 configured as 3A current capability with a sink device connected, if customer use a GPIO to drive CHG_HI low at this moment, VBUS will reconnect if TPS25810 source more than 1.7A before CHG_HI becomes low?

    Thanks!

    Antony

  • 0 in reply to Antony Lin
    TI__Intellectual 1920 points
    Hi Antony,

    This would only happen when you change from 3A advertising to 1.5A while the device is sourcing over 1.7A (1.7A is the current limit when the device is set to advertise 1.5A). If the TPS25810 is sourcing below 1.7A and changed to advertise 1.5A, the current limit will not trip and therefore VBUS will not drop.

    Yes. When sourcing more than 1.7A, VBUS will drop below the minimum required voltage and therefore cause the sink to re-establish connection. The TPS25810 maintains a constant output current (ILIM) when an overload condition occurs therefore causing VBUS to drop.

    Thanks,
    Donovan