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MAX1575
(Rev.:2003)

White LED 1x/1.5x Charge Pump for Main and Sub-Displays

Maxim Integrated 

19-3097; Rev 0; 12/03

EVAALVUAAILTAIOBNLEKIT

White LED 1x/1.5x Charge Pump

for Main and Sub-Displays

General Description

The MAX1575 charge pump drives up to four white

LEDs in the main display and up to two white LEDs in

the sub-display with regulated constant current for uni-

form intensity. By utilizing adaptive 1x/1.5x charge-

pump modes and very-low-dropout current regulators,

it achieves high efficiency over the full 1-cell lithium-

battery input voltage range. A 1MHz fixed-frequency

switching allows for tiny external components, and the

regulation scheme is optimized to ensure low EMI and

low input ripple.

The MAX1575 uses an external resistor to set the full-

scale 100% LED current. Two enable inputs, ENM and

ENS, are used for simple on/off controls for the main and

sub-displays, respectively. By repeatedly pulsing either

enable input, the LEDs can be dimmed in multiple steps

down to 5%. Once the desired brightness is set, the

MAX1575 maintains that brightness setting as long as

the enable input is kept high. If an enable input is kept

low for more than 2ms, the LED current for the respec-

tive display is set to zero. If both enable inputs are kept

low for more than 2ms, the MAX1575 enters shutdown.

The MAX1575 is available in a 16-pin 4mm x 4mm thin

QFN package (0.8mm max height).

Applications

Cell Phones with Main and Sub-Displays

PDAs/Smart Phones with Up to Six White LEDs

Pin Configuration

TOP VIEW

12 11 10 9

C1N 13

IN 14

C2N 15

C1P 16

MAX1575

1234

8 LED4

7 LED5

6 LED6

5 ENM

THIN QFN

4mm x 4mm

Features

♦ Powers Main and Sub-Display LEDs

♦ 85% Average Efficiency (PLED / PBATT) Over Li+

Battery Discharge

♦ 2% LED Current Matching

♦ Up to 30mA/LED Drive Capability

♦ Adaptive 1x/1.5x Mode Switchover

♦ Low Input Ripple and EMI

♦ Individual 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

♦ 16-Pin Thin QFN 4mm x 4mm Package

Ordering Information

PART

MAX1575ETE

TEMP RANGE PIN-PACKAGE

-40°C to +85°C 16 Thin QFN 4mm x 4mm

Typical Operating Circuit

1µF

2.7V TO 5.5V

1µF

ENABLE MAIN

ON/OFF

AND DIMMING

ENABLE SUB

ON/OFF

AND DIMMING

RSET

C1P

IN

C1N

OUT

MAX1575

GND

LED1

LED2

ENM

LED3

ENS

SET

C2P

LED4

LED5

LED6

C2N

1µF

MAIN

SUB

1µF

________________________________________________________________ Maxim Integrated Products 1

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.

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