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BQ24400

Johann Sølvsteen
Prodigy 10 points
Other Parts Discussed in Thread: BQ24400

Hello.

I have made a new NIMH charger design with the BQ24400. The design is almost like the design example in the date sheet.

The charger shall charge a 3-cell NIMH block. I have chosen Bat input voltage devider as followed R6 200K and R7 160K.

That should give a Cell voltage of around 1.5V.

The problem is that it never stops charging, because it regulates the current down so that i never reaches the cell Voltage of 1.5V.

Can You heltp me out here and may be come up with a design example

  • 0
    TI__Mastermind 31120 points

    Set the regulation voltage at 1.7 to 1.8V per cell to insure the charger never comes out of constant current mode.

    The termination detects a drop in cell voltage by reaching full capacity, which warms the cell and causes the impedance to drop.  The drop in impedance along with the constant current give the -dV.