2nd-Level Overvoltage Protection for 2, 3, or 4 Cell LiIon & LiPoly Batteries (2nd Lev Protection)

The bq29400, bq29400A, bq29401, and bq29405 are BiCMOS secondary protection ICs for 2-, 3-, or 4-cell Lithium-Ion battery packs that incorporate a high-accuracy precision over voltage detection circuit. They include a programmable delay circuit for over voltage detection time.

Each cell in a multiple cell pack is compared to an internal reference voltage. If one cell reaches an overvoltage condition, the protection sequence begins. The bq2940x device starts charging an external capacitor through the CD pin. When the CD pin voltage reaches 1.2 V, the OUT pin changes from a low level to a high level.