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BQ25790: continuous 5V output from BQ25790 using 3.7V Li-ION Battery and also during charging

Dhiraj Phadte
Prodigy 60 points
Part Number: BQ25790

Can we get continuous 5V  output from BQ25790 using 3.7V Li-ION Battery and also during charging? Our Processor board needs 5V.

We wanted one IC solution so if BQ25790 is sufficient or Is there any other single IC solution you can suggest 

  • 0
    TI__Guru**** 166176 points

    Hi Dhiraj,

    TI's NVDC chargers like BQ25790 are only intended to provide a minimum system (MINSYS) voltage, typically close to 3.6V, at SYS with a discharged battery at BAT and then SYS follows the battery up to regulation voltage (BATREG).  The BQ25790 is somewhat unique in that it allows the MINSYS voltage to be set slightly higher than BATREG.  So, it is possible, with this charger family, to set MINSYS to 5V with BATREG = 4.2V.  However, the issue is the losses across the internal BATFET being quite high PLOSS = (5V-VBAT) x ICHG.  These losses cause the charger to enter thermal regulation, which reduces charge current, potentially to zero.  If ICHG is low (1A or lower), it might work. Unfortunately, I do not have any test data for this configuration. If you want to try it, I recommend using the 2.2uH inductor and 750kHz switching frequency for highest efficiency. 

    Most customers have a dc/dc boost converter to step up the charger's SYS voltage output to 5V.

    Regards,

    Jeff