LINEAR TECHNOLOGY LT1769 1769fa Constant-Current Constant-Voltage 2A Battery Charger with Input Current Limiting

LT1769

Constant-Current/

Constant-Voltage 2A Battery Charger with Input Current Limiting

FEATURES DESCRIPTIO

Simple Solution to Charge Ni Cd, Ni MH 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 (Ni MH) and nickel-cadmium (Ni Cd) 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

The LT1769 can charge batteries ranging from 1V to 20V.

Shutdown Control

Ground sensing of current is not required and the battery’s APPLICATIO S negative terminal can be tied directly to ground. A saturat- ing switch running at 200k Hz gives high charging effi-

Chargers for Ni Cd, Ni MH, 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

TYPICAL APPLICATIO 500Ω

VIN (ADAPTER INPUT)

GND CLP

RS4 11V TO 28V

C1 ADAPTER 1µF CURRENT SENSE

SW CLN

C2 TO MAIN

D1†† VCC

0.47µF SYSTEM LOAD

SS24 CIN* R5†

BOOST

L1** 15µF UNDERVOLTAGE

LT1769

22µH LOCKOUT

D2 COMP1 UV

SPIN VC 300Ω

10k RPROG

CPROG 4.93k

OVP SENSE BAT 0.33µF

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 RS1 R3

CERAMIC SURFACE MOUNT 0.05Ω 22µF

0.25% Li-Ion

**22µH SUMIDA CDRH125 BATTERY CURRENT TANT

†SEE APPLICATIONS INFORMATION FOR SENSE BATTERY

VOLTAGE SENSE 1511 • F01

INPUT CURRENT LIMIT AND UNDERVOLTAGE LOCKOUT ††GENERAL SEMICONDUCTOR. FOR TJ LESS THEN 100°C

MBRS130LT3 CAN BE USED 162k

Figure 1. 2A Lithium-Ion Battery Charger

1769fa