General Description

The MAX1570 fractional charge pump drives up to five

white LEDs with regulated constant current for uniform

intensity. The MAX1570 maintains the highest possible

efficiency over the full 1-cell lithium-ion (Li+) battery

input voltage range by utilizing a 1x/1.5x fractional

charge pump and very-low-dropout current regulators.

The MAX1570 operates with 1MHz fixed-frequency

switching, allowing for tiny external components. The

regulation scheme is optimized to ensure low EMI and

low input ripple.

An external resistor sets the full-scale LED current,

while two digital inputs control on/off and select

between three levels of brightness. A pulse-width mod-

ulation (PWM) signal can also be used to modulate LED

brightness.

QFN packaging (0.8mm max height).

Applications

White LED Backlighting

Cell Phones and Smart Phones

PDA and Palmtop Computers

Portable MP3 Players

Digital Cameras and Camcorders

Features

o Excellent 0.3% LED-to-LED Current Matching

o 30mA/LED Drive Capability

o Proprietary 1x/1.5x Modes for Ultra-High

Efficiency

o Low Input Ripple and EMI

o Eliminates Ballast Resistors

o Digital or PWM LED Dimming Control

o 0.1µA Shutdown Current

o 2.7V to 5.5V Supply Voltage Range

o Soft-Start Limits Inrush Current

o Thermal-Shutdown Protection

o No External Inductor, Schottky, or Zener Diode

Required

White LED Current Regulator with 1x/1.5x

High-Efficiency Charge Pump

________________________________________________________________ Maxim Integrated Products

1

16

15

14

13

9

10

11

12

SET

EN1

PGND

C1N

4

3

2

1

LED5

GND

EN2

C1P

56

7

8

LED4 LED3 LED2 LED1

MAX1570

C2N OUT C2P IN

THIN QFN

(4mm x 4mm)

Pin Configuration

Ordering Information

LED1

LED2

LED3

LED4

LED5

4.7

µF

PGND

GND

C1P

C1N C2P

C2N

1

µF1µF

EN1

EN2

SET

IN

RSET

1

µF

2.7V TO 5.5V

ON/OFF

AND

DIMMING

1x/1.5x

REGULATING CHARGE PUMP

REFERENCE

AND

CONTROL

LOW-DROPOUT

CURRENT

REGULATORS

MAX1570

OUT

Typical Operating Circuit

19-2526; Rev 0; 7/02

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.

PART

TEMP RANGE

PIN-PACKAGE

MAX1570ETE

-40°C to +85°C

16 Thin QFN