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TPS2549: with external High-side Switch solution

Koshi Ninomiya
Expert 5505 points
Part Number: TPS2549
Other Parts Discussed in Thread: TPS2546

Dear Team,

My customer is considering to use TPS2549 at USB Port of their module.

But they require very low Rds_on on high-side switch. Then, they are thinking the following application.

 

[Very low Rds_on High-side Switch Device] ------(VBUS)

   +

[TPS2549 for USB Charging Port Controller] -----(D+ & D-)

 

 

When operation Port type of the TPS2549 is set only “Dedicated Charging Port (DCP) Mode”, the above application is OK, right?

 

When operation Port type is set “CDP-SDP Auto Switch Mode”, the above application is not OK, because there is OUT discharge operation under CDP-SDP Auto Switch mode, right?

Under the CDP-SDP Auto Switch Mode, when they want to use the external very low Rds_on High-side Switch Device, how should they do?

Thank you.

 

Best Regards,

 

Koshi Ninomiya

  • 0
    TI__Mastermind 32941 points
    Koshi,

    I am not sure that you will be able to use the TPS2549 in the way that the customer is wanting. The port is required to be able to discharge the bus in several conditions and the TPS2549 was not conceived to work with an external Fet.

    Your customer would have to connect the TPS2549 to the input power source and detect when it does a discharge and discharge the bus on their own. Cable Compensation will not work.

    It might be possible to utilize the TPS2546 for this purpose, but I will have to study the datasheet and get back to you.

    Does your customer have a discharge detection plan for VBUS?

    I will get back to you in a few days after I study the TPS2546 datasheet to target this solution.

    TI would not be able to guarantee compliance in this mode of operation because we will not be in direct control of the VBUS.
  • 0 in reply to Chuck Branch
    TI__Mastermind 32941 points
    Koshi,

    I do not recommend the TPS2549 with an external power switch. There are too many possible error conditions to fully resolve.

    Regards,
    Chuck