LT1511 Constant-Current/ Constant-Voltage 3A Battery Charger with Input Current Limiting UFEATURESDESCRIPTIO ■ Simple Design to Charge NiCd, NiMH and Lithium The LT®1511 current mode PWM battery charger is the Rechargeable Batteries—Charging Current simplest, most efficient solution to fast charge modern Programmed by Resistors or DAC rechargeable batteries including lithium-ion (Li-Ion), nickel- ■ Adapter Current Loop Allows Maximum Possible metal-hydride (NiMH) and nickel-cadmium (NiCd) that Charging Current During Computer Use require constant-current and/or constant-voltage charg- ■ Precision 0.5% Accuracy for Voltage Mode Charging ing. The internal switch is capable of delivering 3A* DC ■ High Efficiency Current Mode PWM with 4A Internal current (4A peak current). Full-charging current can be Switch programmed by resistors or a DAC to within 5%. With 0.5% ■ 5% Charging Current Accuracy reference voltage accuracy, the LT1511 meets the critical ■ Adjustable Undervoltage Lockout constant-voltage charging requirement for Li-Ion cells. ■ Automatic Shutdown When AC Adapter is Removed A third control loop is provided to regulate the current ■ Low Reverse Battery Drain Current: 3µA drawn from the AC adapter. This allows simultaneous ■ Current Sensing Can Be at Either Terminal of the Battery operation of the equipment and battery charging without ■ Charging Current Soft-Start overloading the adapter. Charging current is reduced to ■ Shutdown Control keep the adapter current within specified levels. U The LT1511 can charge batteries ranging from 1V to 20V. APPLICATIO S Ground sensing of current is not required and the battery’s negative terminal can be tied directly to ground. A saturat- ■ Chargers for NiCd, NiMH, Lead-Acid, Lithium ing switch running at 200kHz gives high charging effi- Rechargeable Batteries ciency and small inductor size. A blocking diode is not ■ Switching Regulators with Precision Current Limit required between the chip and the battery because the chip goes into sleep mode and drains only 3µA when the , LTC and LT are registered trademarks of Linear Technology Corporation. *See LT1510 for 1.5A Charger wall adapter is unplugged. U D3 R7† MBRD340 TYPICAL APPLICATIO 500Ω VIN (ADAPTER INPUT) GND CLP R † 11V TO 28V S4 C1 ADAPTER 1µF SW CLN CURRENT SENSE C2 TO MAIN D1 V 0.47µF CC + + SYSTEM POWER MBRD340 BOOST C R5† 10µF IN* L1** 10µF UNDERVOLTAGE LT1511 20µH LOCKOUT COMP1 UV D2 MBR0540T 200pF R6 PROG 5k SPIN VC 300Ω RPROG OVP SENSE BAT 4.93k 1k CPROG 1% 1µF RS3 RS2 NOTE: COMPLETE LITHIUM-ION CHARGER, 0.33µF 200Ω 200Ω NO TERMINATION REQUIRED. RS4, R7 1% 1% AND C1 ARE OPTIONAL FOR IIN LIMITING VBAT *TOKIN OR UNITED CHEMI-CON/MARCON R R3 + S1 + COUT CERAMIC SURFACE MOUNT 0.033Ω 390k 4.2V 22µF **20µH COILTRONICS CTX20-4 2 Li-Ion BATTERY CURRENT 0.25% + TANT †SEE APPLICATIONS INFORMATION FOR SENSE BATTERY 4.2V INPUT CURRENT LIMIT AND UNDERVOLTAGE LOCKOUT VOLTAGE SENSE 1511 • F01 R4 50pF 162k 0.25% Figure 1. 3A Lithium-Ion Battery Charger 1
