Datasheet

Background
1-2
1.1 Background
The bq2420x series are simple Li-Ion linear charge management devices for
low-cost and space-limited charger applications. The bq2420x series offer
integrated power FET, high-accuracy voltage regulation, temperature
monitoring, charge status, and charge termination—all in a single IC.
The bq2420x works 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 preconditioning phase conditions deeply discharged cells.
Once the battery reaches the charge voltage, the voltage-regulation loop
takes over and completes the charge cycle. Charge is terminated on the basis
of 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 and a recharge feature activated when the
battery voltage falls below the V
RCH
threshold.
In addition to the standard features, the core product provides two additional
enhancements: temperature monitoring and status display. The temperature-
sense 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 charger
operation: charge-in-progress, charge complete, and fault. This output can be
used to drive an LED or to interface with a microcontroller.
1.2 Features
- Performance evaluation of a charge-management solution for portable
applications using the bq2420x product family
- Complete designed-and-tested charger
- Integrated powerFET
- High-accuracy voltage regulation
- Temperature monitoring
- Charge status reporting
- Charge termination
- Up to 500 mA of continuous charge current for single-cell Li-Ion or Li-Pol
applications using a current-limited power supply