The LT1511 current mode PWM battery charger is the simplest, most efficient solution to fast charge modern rechargeable batteries including lithium-ion (Li-Ion), nickel-metal-hydride (NiMH) and nickel-cadmium (NiCd) that require constant-current and/or constant-voltage charging. The internal switch is capable of delivering 3A* DC current (4A peak current). Full-charging current can be programmed by resistors or a DAC to within 5%. With 0.5% reference voltage accuracy, the LT1511 meets the critical constant-voltage charging requirement for Li-Ion cells. A third control loop is provided to regulate the current drawn from the AC adapter. This allows simultaneous operation of the equipment and battery charging without overloading the adapter. Charging current is reduced to keep the adapter current within specified levels. The LT1511 can charge batteries ranging from 1V to 20V. Ground sensing of current is not required and the battery's negative terminal can be tied directly to ground. A saturating switch running at 200kHz gives high charging efficiency and small inductor size. A blocking diode is not required between the chip and the battery because the chip goes into sleep mode and drains only 3µA when the wall adapter is unplugged.
