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BQ25703A: BQ25703a default settings that surely runs ?

Alan Peng1
Prodigy 30 points
Part Number: BQ25703A

Hi, TI tech support team, everyone,

I am using BQ25703A for charging the backup battery of my device.

The main power source will charge the battery to full and stop charging.

When the main power is lost, it switches to this backup battery.

Is there any "default settings" for BQ25703A to use ?

By "default", I mean it definitely works. Current I could read and write 25703A's registers via I2C

(using Linux), and got the response from 25703A, shown as follows.

 

However, when I checked out ADC registers, all values are 0. It supposes that if my

settings are correct, ADC registers will have values (and changing over time).

 

I don't know I missed something. Can you please give me some heads-up ?

Thank you.

Alan

 

  • 0
    TI__Expert 3320 points

    Hi Alan,

         From the setting, looks like your target VBAT=8.4V, Icharge=64mA, IINDPM=3.2A. I think your charge current is too small, this charge current should be your battery fast charge period constant charging current value. 

         I suspect you don't enable ADC yet. You should enable 1 time ADC through setting REG3B[6]=1 or you can enable continuous ADC through REG3B[7]=1 shown below. 

    Regards

    Shishuo

  • 0 in reply to Shishuo Zhao
    Prodigy 30 points

    Hi, Shishuo,

    Thanks for the reply. Over the weekend we used try and error.

    It worked a little bit. It started charging, and yes we did enable ADC (to monitor numbers).

    ADC updates itself approx. every 10 seconds.

    Yes, we did make the current higher than that 64mA. The battery specs say the minimum charging current from 80mA.

    The main specs of this battery is 7.4V, 400mAH.

    However, it did not work with 128mA. It worked from 256mA.

    The nominal voltage of this battery is 7.4V, and its max charging voltage is 8.4V (that's why we set it to 8.4V).

    The current question is: very weird that the 25703a said it's charging (while we kept querying ADC and see the

    number was raising to approx. 7.4v). Sometimes it stopped at 7.1v, or sometimes 7.3v or so.

    It also hit 7.4V quick. Like within few minutes. Is this normal, please, from you standpoint ?

    We are now exhausting the battery to a lower voltage, like 6.1V and see if it stops before 7.4V.

    Alan

  • 0 in reply to Alan Peng1
    TI__Expert 3320 points

    Thanks for update.

    Does this battery holds battery gauge device? If you set maximum charge voltage 8.4V then the charger should not stop before it hit 8.4V.  I would like to know why it stops at 7.1~7.4V.  Maybe it is helpful if you can provide a charge cycle Current and Voltage waveform for further analysis. 

  • 0 in reply to Shishuo Zhao
    Prodigy 30 points

    Hi, Shishuo,

    Enclosed please find the battery specs of this battery. We're actually confused about this.

    Although we did set it to 8.4V, which is max charge voltage, the battery-side gauge (protection

    IC model: HY-2120CB) might stops by itself for some reasons that we don't know ?

    Alan

  • 0 in reply to Alan Peng1
    TI__Expert 3320 points

    Hi Alan,

        Thanks for providing the battery information, it looks fine. Could you monitor the charger status register REG21/20H to see if there is any abnormal status reported? It is also helpful if you can provide a charge cycle Current and Voltage waveform for further analysis.Thanks.

    Regards

    Shishuo

  • 0 in reply to Shishuo Zhao
    TI__Expert 3320 points

    Hi there,

    We haven’t heard back from you. We are assuming you were able to resolve your issue. If not, just post a reply below or create a new thread if the thread has locked due to time-out.

    Regards,