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BQ25703A: Unability to program the max current when charging

Alonso Moran
Prodigy 10 points
Part Number: BQ25703A
Other Parts Discussed in Thread: EV2400, BQSTUDIO

Hello together!

We are developing a device that contains the BQ chip for charging the two batteries of the same device. I would like to reduce the current allowed when charging because the device gets too hot. In page 52 of the datasheet of the component there is the ChargeCurrent registers to modify the current. When I change the registers in code following this guidelines, I can see in the display of my charger that the current is never the one I have programmed. For instance, if I set the current registers to 00 in both sets of bytes (for the MSB and the LSB), I still get current going into my device, when it should be 0. Another example, I set the register to 0x02 in the MSB, meaning there should be 512 mA and my charger shows 950 mA. 

My question is, should I change anything in the charge options in order to make my BQ to set the right current when charging? or what could be the cause of such failure? 

I appreciate if anyone can help.

Thank you!

  • 0
    TI__Mastermind 32965 points

    Hi, Alonso,

    For first time user, we recommend following BQ25703AEVM step-by-step instruction. This failure to program could be related to how to program the device. We recommend BQStudio with EV2400 interface. 

    The minimum registers for charging are charge current() and charge voltage() registers. 

  • 0 in reply to Tiger Zhou
    Prodigy 10 points

    Hi Tiger!

    Thank you for the quick reply. The thing is that we already have a code, developed by a programmer some time ago, that we flash into the device. I think the problem does not come from the programming itself, but for something in the settings (charge option, charge voltage, charge current, ...). Since the current does not seem to change correctly according to the written values on the Charge Current Register, I am limiting the max current via the IIN_HOST for now. Thus, reducing the heat of the BQ. 

    Is there default value that causes the value in the Charge Current Register to be higher than they should?

    Thank you again.

  • 0 in reply to Alonso Moran
    TI__Mastermind 32965 points

    The default charge current is zero. Make sure you read back the register after each write, and confirm the write is success.

  • 0 in reply to Tiger Zhou
    Prodigy 10 points

    Okay, I will try. Thank you very much for the help!