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BQ25306: How to Start Charging with Fast Charge

Shinichi Yokota
Genius 9715 points
Part Number: BQ25306

Hello,

How can I skip the first two steps of trickle charge and pre-charge and start battery charging with the third fast charge step? If it's doable, could you provide me with the way to do it?

Best regards,
Shinichi Yokota

  • 0
    TI__Mastermind 21695 points

    Hi Shinichi Yokota, 

    The device will start charging in the fast charge phase when VBAT > VBAT_LOWV threshold. If battery voltage measured through the feedback resistor divider is below VBAT_LOWV then the device will start charge in either trickle charge or pre-charge phase. There is no way to skip these phases when a battery is deeply discharged. 

    If you wish to avoid charging in pre-charge step you will want to design the system to prevent battery from discharging below VBAT_LOWV threshold (approx. 2.85V for a battery being charged to 4.2V). 

    Best Regards,

    Garrett

  • 0 in reply to Garrett Kreger
    TI__Genius 9715 points

    Garrett,

    If I modify the schematic so that the VBAT is kept above the VBAT_LOWV, does it work as intended?

    Best regards,
    Shinichi Yokota

  • 0 in reply to Shinichi Yokota
    TI__Mastermind 21695 points

    Hi Shinichi, 

    Yes if you make your design so that VBAT does not reduce below VBAT_LOWV the BQ25306 will begin the charge cycle in fast charge step. 

    Mind you I am not quite sure what schematic change you are trying to show above in red. To prevent VBAT dropping below VBAT_LOWV I recommend using a protection IC to prevent battery from discharging too low. 

    Best Regards,

    Garrett