The bq2031 Lead-Acid Fast Charge IC is designed to optimize charging of lead-acid chemistry batteries. A flexible pulse-width modulation regulator allows the bq2031 to control constant-voltage, constant-current, or pulsed-current charging. The regulator frequency is set by an external capacitor for design flexibility. The switch-mode design keeps power dissipation to a minimum for high charge current applications.

A charge cycle begins when power is applied or the battery is replaced. For safety, charging is inhibited until the battery voltage is within configured limits. If the battery voltage is less than the low-voltage threshold, the bq2031 provides trickle-currentcharging until the voltage rises into the allowed range or an internal timer runs out and places the bq2031 in a Fault condition. This procedure prevents high-current charging of cells that are possibly damaged or reversed. Charging is inhibited anytime the temperature of the battery is outside the configurable, allowed range. All voltage thresholds are temperature-compensated.

The bq2031 terminates fast (bulk) charging based on the following: Maximum voltage Second difference of cell voltage (2V) Minimum current (in constant-voltage charging) Maximum time-out (MTO) After bulk charging, the bq2031 provides temperature-compensated maintenance (float) charging to maintain battery capacity.

• Conforms to battery manufacturers' charge recommendations for cyclic and float charge
• Pin-selectable charge algorithms
- Two-Step Voltage with temperature-compensated constant-voltage maintenance - Two-Step Current with constant-rate pulsed current maintenance - Pulsed Current: hysteretic, on-demand pulsed current
• Pin-selectable charge termination by maximum voltage, 2V, minimum current, and maximum time
• Pre-charge qualification detects shorted, opened, or damaged cells and conditions battery
• Charging continuously qualified by temperature and voltage limits
• Internal temperature-compensated voltage reference
• Pulse-width modulation control
- Ideal for high-efficiency switch-mode power conversion - Configurable for linear or gated current use
• Direct LED control outputs display charge status and fault conditions