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Original question:

BQ25895 VBUS/PMID/VSYS interaction

BQ25895: BQ25895 VBUS/PMID/VSYS interaction

Raghunath Pol19
Prodigy 10 points
Part Number: BQ25895

Hello,


We are developing an application where we intend to use a BQ25895 with a 1 cell Li-Ion battery as a power bank: we need to be able to charge the battery from VBUS, and output 5V@3.1A on PMID to charge external devices. we are using the BQ25895 in host mode with a microcontroller that talks to it over I2C.  have some questions pls clarify.

 From what I understand, if only VBUS is present, the internal converter will be in buck mode charging the battery, 

1. When VBUS is present will get 5V@3.2A at PMID but will it simultaneously charge battery Icharge@5A ?

Regards,

Raghu

  • 0
    TI__Guru**** 166616 points
    Raghunath,

    No. When VBUS is present, the charger is in charging mode. V(PMID) = V(VBUS)-I(VBUS)*RDSONq1. Any current you pull from PMID will not be available to the buck converter to charge the battery. When VBUS is not present, the charger automatically switches to boost mode after a short delay, with the 5.xV boosted output coming from PMID. Also, to charge at 5A, you will need to supply VBUS >= 7V.