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BQ24005: Premature charge termination

Gert Benade
Prodigy 20 points
Part Number: BQ24005

Hi All,

I have been trying to build a dual-cell Li-Ion charger using the BQ24005-PWP chip.

All works well, but the charge termination voltage is around 7.8 V for the two cells instead of the 8.2 V at which the VSEL pin is set. I first did my own PCB lay-out, and after realizing that the charging is terminated prematurely, I used the reference board's design. The VSENSE pin is tied directly to the BATT + terminal. It still stops charging at around 7.8 V and goes into float mode at this voltage. Upon power cycling, it goes into fast-charge mode for a few seconds, and switches over to floating at ~7.8 V.

Any help would be appreciated! Why does it stop at ~7.8 V instead of 8.2 V?

Thanks!

  • 0
    TI__Intellectual 1980 points

    Hello,

    As for the regulation voltage, you should test the voltage near to the BAT pin, near the IC. Other than the voltage of battery.

  • 0 in reply to Kerry Song
    Prodigy 20 points

    Hello Kerry,


    Thank you for your reply.

    On the board that I designed myself I had the sense pin connected directly connected to the Batt pins (18&19), with a short piece of wire connecting the board to the cells. On the second board that I made, I used the evaluation board's layout and brought the pin 17 out, with a 100 ohm pull-up resistor to the Batt pins (according to document SLUU083a.pdf, p. 19).

    The results were within 100 mV the same. Charging is terminated at ~7.8 V.

    Thanks once again for your help. Any suggestions?

    Kind regards,

    Gert