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BQ25122: Battery charging issue

Damien_Effi
Intellectual 495 points
Part Number: BQ25122

Hi,

I am using a BQ25122 to charge a VARTA CP1240A3 battery (Li-ION, 3.7V - 0,2Wh).

I connected a 4,99K resistor to Riset (40mA Icharge)

I connected a 1K resistor to RLim(200mA Ilimit)

I connected a 4,99K resistor to Rtterm (4mA Iprecharge)

I connect a 5V external power supply to IN pin and I have TS voltage to 2,55V

When I measure current with an ampremeter in serial to the battery, I don't have any current. I should have 40mA, right?

Thanks to give me any ideas on what is going wrong.

Regards,

Damien

  • 0
    TI__Genius 10385 points

    Hi Damien,

    In this case, I believe the issue is the TS voltage. As you mentioned, your TS voltage is 2.55V and your input voltage is 5V, indicating that TS voltage is 0.51% of VIN. This would put the device into the TS COLD threshold which shuts off charging.

    Charging only occurs when TS voltage is between the HOT or COLD thresholds, normal charging only occurs when TS voltage is between the WARM and COOL thresholds. This means that TS voltage has to be between 0.75V and 1.99V to charge, and it has to be between 1.025V and 1.8V to charge normally.

    If you don't want to use the TS function and would like to just charge normally, the TS voltage has to be above the TS Disable Threshold (3V).

    Are you planning to use the TS function? If so, what does your TS circuit look like?

    Best Regards,

    Juan Ospina

  • 0 in reply to Juan Ospina
    Intellectual 495 points

    Hi Juan and thanks for your clear explanation.

    I am not using the TS function. So, as you mention, i will put TS level to a voltage above 3V.

    Can I put directly 5V to the TS pin? I don't see max voltage alowed for the TS pin in the datasheet.

    Regards

    Damien

  • +1 in reply to Damien_Effi
    TI__Genius 10385 points

    Hi Damien,

    Typically, for TS disable we recommend a Voltage divider that places the TS voltage above the TS Disable Threshold. The absolute maximum rating for TS voltage is 5.5V so an input voltage variation above this level would be potentially damaging to the device.

    Best Regards,

    Juan Ospina