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BQ25895: BQ25895 query

Bino Mani
Prodigy 90 points
Part Number: BQ25895

Tool/software:

Hello Ti Support Team,


I have a query related to BQ25895. I am designing a battery operated medical device and I want to know how should be the OTG pin connected if I plan to provide the system 5V, 3A through PMID through battery? Is it possible to provide our design 5V, 3A? Battery (Lipo) will be of 3V to 3.7V, 4000mAh. Please note that there won't be any VBUS supply.

Looking forward for a quick response.


Regards,
Bino Mani

  • 0
    TI__Mastermind 26385 points

    Hi Bino, 

    Bino Mani said:
    Is it possible to provide our design 5V, 3A?

    Yes it is possible. BQ25895 can support a maximum boost mode output current of 3.1A and the default boost mode voltage is 5.1V.

    To enable boost mode with PMID pin as output OTG pin must be pulled high. Logic high for OTG pin is minimum 1.3V. You can use any logic rail in your system to pull OTG pin high, but a simple option is connect OTG to battery via a 10kohm resistor. 

    Bino Mani said:
    Please note that there won't be any VBUS supply

    Please note a VBUS supply is required to charge the battery. 

    Best Regards,

    Garrett

  • 0 in reply to Garrett Kreger
    Prodigy 90 points

    Hi Garrett,


    If we want to get 5V, 3.1A output from PMID pin, only OTG pin should be pulled high or we need to configure OTG_CONFIG register too?

  • 0 in reply to Bino Mani
    TI__Mastermind 26385 points

    Hi Bino, 

    As stated in the Boost Mode section of the datasheet (section 8.2.5 on page 19) both OTG pin pulled high and OTG_CONFIG = 1 are required for boost mode to be enabled. 

    On the BQ25895 OTG_CONFIG bit is default set to 1 (shown in table 8-11 on datasheet page 35). Therefore, no I2C communication is required to enable boost mode on the BQ25895. 

    Best Regards,

    Garrett 

  • 0 in reply to Garrett Kreger
    Prodigy 90 points

    Hello Garrett,

    What is the OTG_CONFIG bit is set to 0 and OTG pin is pulled high? What will be the PMID output? 

  • 0 in reply to Bino Mani
    TI__Mastermind 26385 points

    Hi Bino, 

    For the case where OTG_CONFIG is 0 and OTG pin is pulled high boost mode is not enabled. PMID output will be a voltage below battery voltage due to a current path from battery through the body diode of the HSFET (Q2). 

    Best Regards,

    Garrett