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BQ25672: Application issues of chips

Tonyx.wu
Genius 3995 points
Part Number: BQ25672

Tool/software:

During the debugging process of 25672, we found that our battery voltage was 8.2V, the Vbat sampled by the chip ADC was around 8.3V, and the default Vbat_ovp was 8.4V. However, when EN_CARGE was turned on, charging could not be performed, and the chip would generate a battery overvoltage alarm and VinDPM.FIG-INT; We need to adjust Vbat_oVP to above 9V in order to charge the 8.2V battery. What is the reason and how can we solve it?

During the debugging process of 25672, we found that our battery voltage was 8.2V, the Vbat sampled by the chip ADC was around 8.3V, and the default Vbat_ovp was 8.4V. However, when EN_CARGE was turned on, charging could not be performed, and the chip would generate a battery overvoltage alarm and VinDPM.FIG-INT; We need to adjust Vbat_oVP to above 9V in order to charge the 8.2V battery. What is the reason and how can we solve it?
Also, how to set Vbat_oVP, is it an external circuit or a register setting? Do you have detailed instructions on how to operate the register? If there is an external circuit, how should it be set up specifically?

  • 0
    TI__Guru**** 166916 points

    Hi Tony,

    If termination is enabled, BATOVP is fixed percentage above the battery regulation voltage, VREG, as shown below:

    If termination is disabled by setting REG0x0F[1] =0, BATOVP =VREG.

    Can you send a scope plot of V(SYS), V(BAT), I(BAT) when this occurs?

    Regards,

    Jeff

  • 0 in reply to Jeff F
    Genius 3995 points

    We found through the oscilloscope that when the charging enable is turned on, Vbat will have a 1V+voltage spike, which will cause the voltage to trigger OVP, so we cannot turn on charging; This is consistent with the phenomenon that we can charge after increasing the OVP. How did this peak occur and how can it be eliminated?

  • 0 in reply to Tonyx.wu
    TI__Guru**** 166916 points

    Hi Tony,

    Voltage spike is expected at charge turn on when no battery and only the minimum recommend capacitance is attached at BAT pin.  I have never seen a spike like that when a battery or equivalent capacitance > 200uF is connected at BAT pin.  Regardless, the OVP event clears as soon as the voltage drops below the OVP threshold. If you add more low ESR capacitance at BAT, does that prevent OVP event?   Does the BAT OVP flag (and status, temporarily) trip, then charge status stays in termination?  If the recharge thershold in REG0x0A[3:0] is lowered to 0000 = 50mV, does charge restart?  

    Regards,

    Jeff