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bq51050B with USB charging

Manuel Campos Monteiro
Prodigy 40 points
Other Parts Discussed in Thread: BQ51050B

Hi,


I'm developing a solution on which a Li-ion battery should be charged over USB or wireless. For that purpose I'm using the bq51050B and followed the schematic available on the datasheet.

As a starting point, I 'm just testing the USB charging option without satisfactory results. The bq51050B seems to be completely shutdown and the battery is not charging. After trying to debug the problem a doubt was raised and I'm not completely sure if the bq51050B is capable of charging the battery over USB, or just over wireless. Can you please elucidate me about that issue? I have noticed that in the datasheet there is a block named "wired charger", what is this block supposed to be?

Nevertheless, while trying to charge the battery over USB just using the bq51050B I have noticed that, despite having AD>3.6V, the pin /chg is never set to 0. Is there any reason for this to be happening?

Thanks,


Manuel

  • 0
    Intellectual 970 points

    The "Wired Charger" block appears to be another device with its own current sensing and voltage limiting, perhaps something like an LTC4054. The AD function is just a sense to disable the wireless charger. 

  • 0
    TI__Genius 14890 points

    Manuel,

    The bq51050B can only charge through the Wireless power path.  The “Wired Charger” shows that if non-wireless charging is required, a charger specific to the wired power path must be used.  For linear charging, the bq2407x family is a good option.  For switching, the bq2425x family is a good option.  Both options can run up to 1.5A.

    The second part of the question asks why /CHG is not pulling to ground.  Since the bq51050B receives its power from the wireless power transfer, without that power, it cannot drive the /CHG output FET which would pull the output to ground. The bq51050B uses the AD pin to detect that an adapter (5V) is plugged in.  When it detects the adapter the Wireless Power is  tuned off (by sending an End Power Transfer (EPT) message to the transmitter), then the AD_EN will turn on the FET to allow the discrete charger to charger the battery from the adapter.  When the transmitter receives the EPT, it can then go to a low power mode reducing power consumption.

    Regards,

    Dick

  • 0 in reply to Dick Stacey
    Prodigy 40 points

    Dear Dick,


    Thank you very much for your explanation. It has been very helpful.

    I will look for one of the bq2407x devices in order to enable also wired charging.

    Best regards,

    Manuel

    P.S.: I also would like to thanks Mike for his help.