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BQ2004 design

Hans-Ulrich Zerbst
Prodigy 45 points
Other Parts Discussed in Thread: BQ2004

Hi,

I have a problem to integrate a BQ2004 into my design. It is to charge a 10-cell NiMH battery with C/2 current. On start up it immediately jumps into trickle charge and the LED outputs (in mode 3) show that fast charge is complete. TM1 and TM2 are set to VCC and Float, respectively. I do not use the discharge facility. TCO and TS are left open, INH is tied to VCC.

Looking at VBAT and VSNS gives VCELL = 2.4V, which is below VMCV and above VEDV.

Is there anything a novice user can do wrong with this charge controller?

Best regards - Max

 

  • 0
    TI__Guru**** 150900 points

    You need to configure the TS and TCO pins.  They cannot be left open.  From page 5 of the datasheet: "VTCO is the voltage presented at the TCO input pin, and is configured by the user with a resistor divider between VCC and ground. The allowed range is 0.2 to 0.4 ∗ VCC.  If the temperature of the battery is out of range, or the voltage is too low, the chip enters the charge pending state and waits for both conditions to fall within their allowed limits. The MOD output is modulated to provide the configured trickle charge rate in the charge pending state. There is no time limit on the charge pending state; the charger remains in this state as long as the voltage or temperature conditions are outside of the allowed limits."

    This user's guide shows how they are setup on the EVM: http://focus.ti.com/lit/ug/sluu014/sluu014.pdf

    You need to configure TCO and TS to operate in the appropriate ranges.  You can use a 10k resistor, if you do not want to use a thermistor.

  • 0 in reply to Chris Glaser
    Prodigy 45 points

    Thanks for your very prompt response. It seems to work now.

    Regards - Max