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BQ24133: Battery Overcharge Problem

Gor Hovsepyan
Intellectual 390 points
Part Number: BQ24133

Dear Support team, 

I am using BQ24133 battery charger and I am using only single cell LiIon battery, SChematics is attached. But after 4.2V it continues to charge even up to 4.7V.  Could you please say what part is wrong?

  • 0
    TI__Expert 8690 points
    Hi Gor,

    Did you use kelvin connection on the SRP/SRN traces to the sense resistor? Make sure there is no current going through these traces, as it will create a voltage drop and measure the wrong value.

    Regards,
    Steven
  • 0 in reply to Steven Bangdiwala
    Intellectual 390 points

    Hello Steven,

    I guess it is not a Kelvin connnection, please find the layout attached. Sence resistor is just under the arrow.

    Is there any way to change sense resistor value to fix it?

    Could you please suggest a way to measure current through these traces.

  • 0 in reply to Gor Hovsepyan
    TI__Expert 8690 points
    Gor,

    There is no quick way to fix it by just changing the sense resistor. The problem is that the voltage reaching through the SRN pin to the charger does not represent the correct battery voltage.

    The best way to route SRP and SRN is to use small traces and connect them directly to the sense resistor. Do not allow any high current to pass through these traces, this is what we call the Kelvin connection. You can check the datasheet on pages 30 and 31 for our layout guidelines. Figure 24 shows how to connect SRP and SRN.

    Regards,
    Steven