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BQ25883: Control OTG mode by hardware?

reto hermann
Intellectual 740 points

Part Number: BQ25883
Other Parts Discussed in Thread: BQ25886

Hi,

we are using the BQ25883 in combination with a AM335x processor. The two devices are sharing same USB connector because we want to use this USB port for both battery charging and as US OTG port of the processor. 

To control VBUS the AM335x has an output called "DRVVBUS" that typically controls an external high side switch to turn on and off VBUS depending on the OTG role. 

With our setup the high side switch is integrated in the BQ25883 and unfortunately there is no input pin for the DRVVBUS signal. To control the OTG mode of the  BQ25883  there is a register bit (REG06 / EN_OTG) that can be set using the i2c interface.

We have tried to synchronize the OTG Mode of the BQ25883 and the DRVVBUS  signal by software but we have several issues with that solution.

My questions are:

1: Is there a way to control the OTG mode of the BQ25883 by hardware?

2: Is there maybe another, similar charger IC that has such an input pin?

Thank you for help!

BR

Reto

  • 0
    TI__Genius 11850 points

    Hi Reto,

     

    In your application, can you set EN_OTG = 1 even while VBUS is connected? If EN_OTG and EN_CHG are both 1, then EN_CHG takes priority. The BQ25883 will switch to OTG mode when the adapter is removed, as shown in Figure 79.

      

     

      

    Alternatively, you can consider the BQ25886, which is a standalone charger that has an OTG pin. You can pull this pin high or low to enable/disable OTG mode.

     

    Best regards,

    Angelo

  • 0 in reply to Angelo Zhang87
    Intellectual 740 points

    Hi Angelo, thank you for your quick reply!

    As far as I understand USB OTG is more complex that just turning VBUS on. For example there is a mode called Attach Detection Protocol (ADP). In this mode the capacitance on the USB port is measured periodically  to determine whether there is another device attached, a dangling cable, or no cable. So I'm afraid that just turning EN_OTG on all the time will not do the job.

    Thank you for the suggestion of the BQ25886 device. We will check if that is an option for us.


    Best regards
    Reto