1

LTC3490

3490fa

■

Portable Lighting

Single Cell Minimum Component LED Driver

Single Cell 350mA

LED Driver

■

350mA Constant Current Output

■

2.8V to 4V Output Compliance

■

1- or 2-Cell NiMH or Alkaline Input

■

Synchronous Rectification: Up to 90% Efficiency

■

Fixed Frequency Operation: 1.3MHz

■

Low Quiescent Current: <1mA

■

Very Low Shutdown Current: <50

µA

■

Open LED Output Limited to 4.7V

■

■

Dimming Control

■

Undervoltage Lockout to Protect Batteries

■

Low Profile (0.75mm) 3mm

× 3mm Thermally

Enhanced 8-Lead DD and S8 Packages

FEATURES

DESCRIPTIO

APPLICATIO S

TYPICAL APPLICATIO

The LTC

LED applications. It is a high efficiency boost converter

that operates from 1 or 2 NiMH or alkaline cells and

generates 350mA of constant current with up to 4V of

compliance. It contains a 100m

Ω NFET switch and a

130m

Ω PFET synchronous rectifier. The fixed switching

frequency is internally set to 1.3MHz.

The LTC3490 limits the output voltage to 4.7V if the output

load is disconnected. It also features an analog dimming

capability that reduces the drive current proportional to

the CTRL/SHDN pin voltage. A low-battery logic output

signals when the battery has dropped below 1V/cell. An

undervoltage lockout circuit shuts down the LTC3490

when the battery voltage drops below 0.85V/cell. The

feedback loop is internally compensated to minimize com-

ponent count.

+

SW

CAP

ON/OFF

LED

1 NiMH OR

ALKALINE

CELL

4.7

µF

LOBAT

3490 TA01

CTRL/SHDN

CELLS

1M

HIGH

CURRENT

LED

GND

LTC3490

3.3

µH

350mA

1

0

10

30

40

50

100

70

1.5

2

3490 TA02

20

80

90

60

2.5

3

, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.

All other trademarks are the property of their respective owners.