BQ2057

The BENCHMARQ bq2057 series advanced Li-Ion linear charge-man-agement ICs are designed for cost-sensitive and compact portable electronics. They combine high-accuracy current and voltage regulation,battery conditioning, temperature monitoring, charge termination,charge-status ndication, and AutoComp charge-rate compen-sationinasingle8-pinIC.


The bq2057 continuously measures battery temperature using an external thermistor. For safety reasons,the bq2057 inhibits charge until the battery temperature is within user-defined thresholds. The bq2057 then charges the battery in three phases: conditioning, constant current, and constant voltage. If the battery voltage is below the low-voltage threshold VMIN, the bq2057 trickle-charges to condition the battery. The conditioning charge rate is set at 10% of the regulation current. The conditioning current also minimizes heat dissipation in the external pass-element during theinitialstageofcharge.


After conditioning, the bq2057 applies a constant current to the battery. An external sense-resistor setsthe magnitude of the current. The sense-resistor can be on either the low or the high side of the battery without additional components. The constant-current phase continues until the  attery reaches the charge-regulationvoltage.


The bq2057 then begins the constant-voltage phase. The accuracy of the voltage regulation is better than ±1% over the operating-temperature and supply-voltage ranges. For single and dual cells with either coke or graphite anodes, the bq2057 is offered in four fixed-voltage versions:4.1V, 4.2V, 8.2V, and 8.4V. Charge stops when the current tapers to the charge termination threshold, VTERM. The bq2057 automatically restarts the char