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bq51025 / to implement OTG function

K.Yaita
Guru 29690 points
Other Parts Discussed in Thread: BQ24192I, BQ51025, BQ51013B

Hi Team,

My customer is currently evaluating bq51025, bq24192i and bq27531(all TI solution) for the following system.


He would like to implement OTG function(the route of red arrow), however it couldn't operate well because Q1 is off when there is no supply at USB micro-B connector.
That is AD pin of bq51025 prevents OTG function.

He adopted the solution because he would like to switch USB supply and Wireless supply automatically, however OTG function couldn't be available.
Do you have any advice to realize OTG function for this system?

Your support would be really appreciated.

Best Regards,
Yaita / japan disty

  • 0
    TI__Guru 65796 points
    Hello Yaita
    The bq51025 does not have USB OTG feature. But the bq51013B does have this option.
  • 0 in reply to Bill Johns
    Guru 29690 points

    Bill-san,

    Thank you for your reply.
    I understood bq51013B has OTG feature.

    However, my customer wants to use bq51025(10W) for his system.
    Do you have any solution to realize OTG function using bq51025?

    Best Regards,
    Yaita 

  • 0 in reply to K.Yaita
    TI__Genius 14890 points

    Yaita-san,

    I have a suggestion that might help with implementing OTG on the bq51025.

    Use a high-resistance FET or switch to tie OUT to AD.  To enable OTG, turn the switch on.  This pulls the AD pin high which will in turn, enable AD_EN.  When AD_EN is low, the back-back FET will turn on and allow OUT to go straight to the USB connector.  Using a high-resistance FET allows for a smaller footprint and lower cost.  This FET will not be used to supply current.  When the AD_EN pin goes low, the FET can be turned off and OUT to USB path will still be enabled.

    Note, to disable this path, the OUT pin voltage (VBUS in this case) must be turned off. Turing off VBUS then lets AD go back low and the system turns off.

    Regards,

    Dick

  • 0 in reply to Dick Stacey
    Guru 29690 points

    Hi Dick-san,

    Thank you for your helpful suggestion!

    My customer considers the following solution by looking at your solution.
    He added diodes that prevent the path from USB connector to OUT.


    Is this solution reasonable for you?

    Best Regards,
    Yaita

  • 0 in reply to K.Yaita
    TI__Genius 14890 points
    Yaita-san,

    This solution looks reasonable to be. I have not verified it in the lab, but it should work.

    AD can be pulled high by either the USB connector or by the Application Processor controlling the ON/OFF. The diodes present any backflow from going through that path.

    Regards,

    Dick