Datasheet LT1769 (Analog Devices)

LT1769 Constant-Current/ Constant-Voltage 2A Battery Charger with Input Current Limiting
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Simple Solution to Charge NiCd, NiMH and Lithium
The LT®1769 current mode PWM battery charger is a
Rechargeable Batteries—Charging Current
simple, efficient solution to fast charge modern recharge-
Programmed by Resistors or DAC
able batteries including lithium-ion (Li-Ion), nickel-metal- ■
Adapter Current Limit Allows Maximum Possible
hydride (NiMH) and nickel-cadmium (NiCd) that require
Charging Current During System Use*
constant-current and/or constant-voltage charging. The ■
Precision 0.5% Accuracy for Voltage Mode Charging
internal switch is capable of delivering 2A** DC current ■
Available in 20-Lead Exposed Pad TSSOP and
(3A peak current). Charge current can be programmed by
28-Lead Narrow SSOP Packages
resistors or a DAC to within 5%. With 0.5% reference voltage ■ High Efficiency Current Mode PWM with 3A Internal accuracy, the LT1769 meets the critical constant-voltage Switch charging requirement for Li-Ion cells. ■ 5% Charge Current Accuracy A third control loop is provided to regulate the current ■ Adjustable Undervoltage Lockout drawn from the input AC adapter. This allows simulta- ■ Automatic Shutdown When AC Adapter is Removed neous operation of the equipment and battery charging ■ Low Reverse Battery Drain Current: 3µA without overloading the adapter. Charge current is reduced ■ Current Sensing Can Be at Either Terminal of the Battery to keep the adapter current below specified levels. ■ Charging Current Soft Start ■ Shutdown Control The LT1769 can charge batteries ranging from 1V to 20V. Ground sensing of current is not required and the battery’s
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negative terminal can be tied directly to ground. A saturat-
APPLICATIO S
ing switch running at 200kHz gives high charging effi- ■ Chargers for NiCd, NiMH, Lead-Acid, Lithium ciency and small inductor size. A blocking diode is not Rechargeable Batteries required between the chip and the battery because the ■ Switching Regulators with Precision Current Limit chip goes into sleep mode and drains only 3µA when the , LTC and LT are registered trademarks of Linear Technology Corporation. wall adapter is unplugged. *US patent number 5,723,970 **See LT1510 for 1.5A charger; see LT1511 for 3A charger
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D3††
TYPICAL APPLICATIO
R7† SS24 500Ω VIN (ADAPTER INPUT) GND CLP R † 11V TO 28V S4 C1 ADAPTER 1µF SW CLN CURRENT SENSE C2 TO MAIN V D1†† 0.47µF CC C SYSTEM LOAD SS24 BOOST IN* R5† 15 L1** µF UNDERVOLTAGE LT1769 22µH LOCKOUT D2 COMP1 UV 1N4148 R6 2nF PROG 5k SPIN VC 300Ω 10k RPROG C OVP SENSE BAT PROG 4.93k 0.33µF 1µF 1% RS3 RS2 NOTE: COMPLETE LITHIUM-ION CHARGER, 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 0.05Ω 390k 8.4V 22µF **22µH SUMIDA CDRH125 BATTERY CURRENT 0.25% Li-Ion TANT †SEE APPLICATIONS INFORMATION FOR SENSE BATTERY INPUT CURRENT LIMIT AND UNDERVOLTAGE LOCKOUT VOLTAGE SENSE 1511 • F01 ††GENERAL SEMICONDUCTOR. FOR TJ LESS THEN 100°C R4 MBRS130LT3 CAN BE USED 162k 0.25%
Figure 1. 2A Lithium-Ion Battery Charger
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