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BQ25620: Component schematic and A/D sensitivity

Stefano Sivera
Prodigy 221 points
Part Number: BQ25620
Other Parts Discussed in Thread: BQ25622, BQ25628,

Dear Guys,

I'm finding a LI-Ion charger with power path and our assigned FAE have suggested BQ25622; below the schematic

One question about Q4: the leackage body diode is not drawed (same diode of Q1,Q2,Q3) but I suppose that is present because is present on each MOSFET. In tis case when Q4 is open the current continue to flow to the load through the body diode; can you explain ?

The A/D converter sensitivity is 4 mA; but I need a better sensitivity; can you suggest an alternative components ?

Thank you for your help

Best regards

Stefano Sivera

  • 0
    TI__Mastermind 31090 points

    Hello Stefano, 

    In the application diagram you reference Q4 specifically does not have a body diode drawn as it is different than Q1, Q2, and Q3 FETs. Details on exactly how Q4 work cannot be shared as the design is proprietary, but I can share Q4 BATFET has the ability to prevent current flow in either direction (i.e. Q4 can be turned off to prevent charge current to battery as well as discharge current out of battery).

    Stefano Sivera said:
    The A/D converter sensitivity is 4 mA; but I need a better sensitivity; can you suggest an alternative components ?

    The A/D converter on our charger devices is mainly for reference. If you require better sensitivity I recommend you look to utilize a battery gauge IC.

    Best Regards,

    Garrett 

  • 0 in reply to Garrett Kreger
    Prodigy 221 points

    Hello Garret,

    thank you for support. The request of the current monitor is due to requesto of diconnect the load when the load current is below some mA and reconnect the load after some hours, if the load current increase to 20/30mA after 10-20 sec continue to power the load, if the load is below some mA disconnect again . 4mA is more near to the "some mA" that I need measure. In the mean time I see the BQ25628 where the sensitivity is 2mA. What do you think about it ?

    Best Regards

    Stefano 

  • +1 in reply to Stefano Sivera
    TI__Mastermind 31090 points

    Hello Stefano, 

    My recommendation remains the same for both the BQ25620 and BQ25628. The A/D converter is a feature included on the device intended to be for reference only. The A/D accuracy is not specified for either BQ25620 or BQ25628. If you require a highly accurate A/D measurement then a gauge device is recommended. 

    A specific ADC output having a smaller sensitivity means the LSB of the digital output is 2mA compared to 4mA, but it does not indicate the device has better accuracy. 

    Best Regards,

    Garrett 

  • 0 in reply to Garrett Kreger
    Prodigy 221 points

    Hi Garrett, thank you for your help; I agree with your suggestion.

    best regards

    Stefano