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Rainbow Electronics MAX1574 User Manual

General description, Applications, Features

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General Description

The MAX1574 charge pump drives up to three white
LEDs with regulated constant current for uniform intensity.
By utilizing adaptive 1x/2x charge-pump modes and
very-low-dropout current regulators, it achieves 180mA
output drive capability and high efficiency over the 1-cell
lithium-battery input voltage range. Fixed-frequency
(1MHz) switching allows for tiny external components,
and the regulation scheme is optimized to ensure low EMI
and low input ripple.

The MAX1574 uses an external resistor to set the full-
scale 100% LED current. An enable input (EN) is used for
simple on/off control or can be pulsed repeatedly to set
lower LED current in multiple steps down to 5%. Once the
desired brightness is set, the MAX1574 maintains con-
stant LED current as long as EN is kept high. If EN is kept
low for more than 2ms, the MAX1574 enters shutdown.

The MAX1574 is available in a 10-pin 3mm x 3mm TDFN
package (0.8mm max height).

Applications

LCD Backlighting

Camera Strobes/Flashes and Movie Lights

Cell Phones/Smart Phones

PDAs, Digital Cameras, and Camcorders

Features

Up to 180mA (60mA/LED) Drive Capability

83% Average Efficiency (P

LED

/ P

BATT

) Over Li+

Battery Discharge

0.5% (typ) LED Current Matching

Adaptive 1x/2x Mode Switchover

Low Input Ripple and EMI

5% to 100% Dimming Through Single-Wire Serial
Pulse Interface

Low 0.1µA Shutdown Current

2.7V to 5.5V Supply Voltage Range

Soft-Start Limits Inrush Current

Output Overvoltage Protection

Thermal-Shutdown Protection

10-Pin 3mm x 3mm TDFN Package

MAX1574

180mA, 1x/2x, White LED Charge Pump

in 3mm x 3mm TDFN

________________________________________________________________ Maxim Integrated Products

1

TOP VIEW

MAX1574

TDFN

3mm

×

3mm

10

9

8

7

OUT

GND

LED1

LED2

6

LED3

1

2

3

4

IN

EN

CP

CN

4

5

SET

Pin Configuration

Ordering Information

1µF

1µF

MAX1574

LED3

LED2

LED1

OUT

SET

EN

GND

IN

0.22µF

CP

CN

2.7V TO 5.5V

ON/OFF AND

DIMMING

UP TO 180mA

Typical Operating Circuit

19-3117; Rev 0; 12/03

For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.

EVALUATION KIT

AVAILABLE

PART

TEMP RANGE

PIN-
PACKAGE

TOP

MARK

MAX1574ETB

-40°C to +85°C

10 TDFN
3mm x 3mm

ABB