Constant-Current/Constant-Voltage Battery Charger with Preset Voltage and Termination Flag

The LT1571 PWM battery charger is a simple, efficient solution to fast-charge rechargeable batteries including lithium-ion (Li-Ion), nickel-metal-hydride (NiMH) and nickel-cadmium (NiCd) using constant-current and/or constant-voltage control. The internal switch is capable of delivering 1.5A DC current (2A peak current). The onboard current sense resistor (0.1Ω) allows simple charge current programming to within 5% accuracy using a low cost external resistor. The constant-voltage output can be selected for 4.1V or 4.2V per cell with 0.6% accuracy.

LT1571 can charge batteries ranging from 1V to 20V. A saturating switch operating at 200kHz (LT1571-1, LT1571-2) or 500kHz (LT1571-5) gives high efficiency and small charger size. A logic output (flag) indicates Li-Ion near full charge when the charge current drops to 20% of the programmed value. The LT1571-1 and LT1571-2 are in a 28-pin fused lead narrow SSOP power package. The LT1571-5 is in a 16-pin fused lead narrow SSOP power package.

Applications

* Cellular Phones, PDAs, Notebook Computers, Portable Instruments

* Cradle Chargers for Li-Ion, NiCd, NiMH and Lead-Acid Rechargeable Batteries

* Fast Charging of Li-Ion, NiMH and NiCd Batteries

* Simple Charge Current Programming Requires Only One Low Cost, 1/32W Resistor

* High Efficiency Charger with Up to 1.5A Charge Current

* Precision 0.6% Internal Voltage Reference

* Preset Battery Voltages: 4.1V, 4.2V, 8.2V, 8.4V

* 500kHz or 200kHz Switching Frequency Minimizes Charger Size

* Low Reverse Battery Drain Current: 5µA

* Flag Indicates Li-Ion Charge Completion

* 5% Typical Charge Current Accuracy

* Low Shutdown Current

* LT1571-1: 200kHz, Adjustable Voltage

* LT1571-2: 200kHz, Fixed 8.2V or 8.4V

* LT1571-5: 500kHz, Fixed 4.1V or 4.2V