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BQ25730: Need info regarding the FRS feature

Don Jordan
Prodigy 20 points
Part Number: BQ25730

How can I obtain information regarding the "Fast Role Swap" feature? Can I use this to change when the device goes into and out of OTG mode?

  • 0
    TI__Mastermind 18795 points

    Hi Don,

    The datasheet has a section 9.3.3 Fast Role Swap Feature. This FRS pin is a multiple function pin called "VAP/OTG/FRS". Depending on the register settings, you may enter or exit OTG mode using the same pin. 

    Regards,

    Tiger

  • 0 in reply to Tiger Zhou
    Prodigy 20 points

    Dear Tiger,

    Once again, I thank you for your very prompt reply.

    The OTG/VAP/FRS pin must be hi to /enable/ the OTG and FRS modes, but going into and exiting from an enabled OTG mode is determined by the voltage on VBUS. Specifically, it goes into OTG mode when VBUS goes below Vvbus_convenz and goes out of OTG mode when VBUS goes above ~110% of the voltage programmed into the OTGVoltage() register

    Section 9.3.3 says that the FRS feature will allow the converter to switch from forward mode to OTG mode without dropping VBUS, which is precisely what I need. The section says nothing about /when/ the FRS feature engages, only to contact the factory for mode detail[ed] information about the mode. Can I obtain the mode detailed information about the FRS mode through this forum or do I need to contact the factory?

    Thanks for all of your help!

  • 0 in reply to Don Jordan
    TI__Mastermind 18795 points

    Hi Don,

    You are welcome to contact the factory. Just not sure how much detailed information you are seeking. I might suggest you obtaining a BQ25730EVM  and try it out. 

    Regards

    Tiger

  • 0 in reply to Tiger Zhou
    Prodigy 20 points

    Dear Tiger,

    I think that we have puzzled out the FRS mode swap. Here is how to use it...

    1. Set up the OTG mode.
    2. Enable OTG operation.
    3. Wait until VBUS goes below the voltage programmed into OTGVoltage().
    4. Enable FRS mode swap {3Eh[0] <-- 1b}.

    This will shift the charger into OTG mode without VBUS needing to go all the way to the undervoltage lockout. The key is that FRS must be enabled while VBUS is below the desired OTG voltage. You cannot just leave it enabled.

    We get similar results from both the EVM board and the big brute we built to test this chip out.

    I sincerely thank you for all of your help. Please consider this thread *RESOLVED*.