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.