Constant-Current/Voltage High Efficiency Battery Charger

The LT1505 PWM battery charger controller fast charges multiple battery chemistries including lithium-ion (Li-Ion), nickel-metal-hydride (NiMH) and nickel-cadmium (NiCd) using constant-current or constant-voltage control. Maximum current can be easily programmed by resistors or a DAC. The constant-voltage output can be selected for 3 or 4 series Li-Ion cells with 0.5% accuracy.

A third control loop limits the current drawn from the AC adapter during charging*. This allows simultaneous operation of the equipment and fast battery charging without overloading the AC adapter.

The LT1505 can charge batteries ranging from 2.5V to 20V with dropout voltage as low as 0.5V. Synchronous N-channel FETs switching at 200kHz give high efficiency and allow small inductor size. A diode is not required in series with the battery because the charger automatically enters a 10µA sleep mode when the wall adapter is unplugged. A logic output indicates Li-Ion full charge when current drops to 20% of the programmed value.

The LT1505 is available in a 28-pin SSOP package.

Applications

* Notebook Computers

* Portable Instruments

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

* Simple Charging of Li-Ion, NiMH and NiCd Batteries * Very High Efficiency: Up to 97% * Precision 0.5% Charging Voltage Accuracy * Preset Battery Voltages: 12.3V, 12.6V, 16.4V and 16.8V * 5% Charging Current Accuracy * Charging Current Programmed by Resistor or DAC * 0.5V Dropout Voltage, Duty Cycle > 99.5% * AC Adapter Current Limit* Maximizes Charging Rate * Flag Indicates Li-Ion Charge Completion * Auto Shutdown with Adapter Removal * Only 10µA Battery Drain When Idle * Synchronizable Up to 280kHz