bq24008

The bq2400x series bq24008 ICs are advanced Li-Ion linear charge management devices for highly integrated and space-limited applications. They combine highaccuracy current and voltage regulation; FET passtransistor and reverse-blocking Schottky; battery conditioning, temperature, or input-power monitoring;charge termination; charge-status indication; and charge timer in a small package.

The bq24007 and bq24008 provide the timer-enable function, allowing the host to disable the charge timer when charge current is shared with a load or when the battery is absent. This feature is ideal for applications such as cellular phones, PDAs, and internet appliances.

The bq2400x measures battery temperature using an external thermistor. For safety reasons, the bq2400x inhibits charge until the battery temperature is within the user-defined thresholds. Alternatively, the user of bq24008 can monitor the input voltage to qualify charge. The bq2400x series then charge the battery in three phases:preconditioning, constant current, and constant voltage. If the battery voltage of bq24008 is below the internal low-voltage threshold, the bq2400x uses low-current precharge to condition the battery. A preconditioning timer provides additional safety. Following preconditioning,the bq2400x applies a constant-charge current to the battery. An external sense-resistor sets the magnitude of the current. The constant-current phase is maintained until the battery reaches the
charge-regulation voltage. The bq2400x then transitions to the constant voltage phase. The user can configure the device for cells with either coke or graphite anodes. The accuracy of the voltage regulation is better than ±1% over the operating junction temperature and supply voltage range.

Charge is terminated by maximum time or minimum taper current detection

The bq2400x automatically restarts the charge if the battery voltage falls below an internal recharge threshold.