The bq2420x series are simple Li-Ion linear charge management devices targeted at low-cost and space limited charger applications. The bq2420x series offer integrated powerFET, high-accuracy voltage regulation, temperature monitoring, charge status, and charge termination, in a single monolithic device.
The bq2420x is designed to work with a current-limited wall-mount transformer and therefore does not provide any current regulation. However, these devices offer a fixed internal current limit to prevent damage to the internal powerFET. A time-limited pre-conditioning phase is provided to condition deeply discharged cells. Once the battery reaches the charge voltage, the high accuracy voltage regulation loop takes over and completes the charge cycle. Charge is terminated based on minimum current. An internal charge timer provides a backup safety for charge termination.
Other standard features include an automatic sleep mode activated when VCC falls below the battery voltage falls below the VRCH threshold.
In addition to the standard features, the core product provides two additional enhancements: temperature monitoring and status display. The temperaturesense circuit continuously measures battery temperature using an external thermistor and inhibits charge until the battery temperature is within the user-defined thresholds. The STAT pin indicates three conditions of operation of the charger. These conditions are charge-in-progress, charge complete, and fault. This output can be used to drive an LED or an interface to a microcontroller.