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General Description

The MAX1553/MAX1554 drive white LEDs in series with

a constant current to provide efficient display backlight-

ing in cellular phones, PDAs, and other hand-held

devices. The step-up converter includes an internal

40V, low R

DSON

, N-channel MOSFET switch for high

efficiency and maximum battery life. The MAX1553 has

a current limit of 480mA for driving two to six white

LEDs, while the MAX1554 has a current limit of 970mA

for driving up to 10 white LEDs.

A single analog/PWM Dual Mode input provides two

simple means of brightness adjustment. A separate

enable input provides on/off control. Soft-start minimizes

inrush current during startup.

The MAX1553/MAX1554 are available in space-saving

8-pin TDFN 3mm x 3mm packages.

Applications

Cellular Phones

PDA, Palmtop, and Wireless Handhelds

Color Display Backlight

Features

♦ Constant-Current Regulation for Even LED

Illumination

♦ Internal 40V MOSFET Switch Capable of Driving

10 LEDs

♦ Small, Low-Profile External Components

♦ 2.7V to 5.5V Input Range

♦ Up to 88% Efficiency Driving 6 LEDs

♦ Up to 82% Efficiency Driving 9 LEDs

(20mA, V

= 3.6V)

♦ Analog or PWM Control of LED Intensity

♦ Optimized for Low Input Ripple

♦ Soft-Start to Minimize Inrush Current

♦ 3mm x 3mm 8-Pin TDFN Package

MAX1553/MAX1554

High-Efficiency, 40V Step-Up

Converters for 2 to 10 White LEDs

________________________________________________________________ Maxim Integrated Products 1

TOP VIEW

BRT

GND

5 FB

TDFN

3mm x 3mm

MAX1553

MAX1554

Pin Configuration

Ordering Information

OFF

BRT

GND

2.7V TO 5.5V

INPUT

OVEN

PWM

DC CONTROL

MAX1553

MAX1554

WHITE

LEDS

Typical Operating Circuit

19-2875; Rev 1; 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

M A X1 5 5 3 E TA

-40°C to +85°C 8 TD FN 3m m x 3m m

AGX

M A X1 5 5 4 E TA

-40°C to +85°C 8 TD FN 3m m x 3m m

AGY

Dual Mode is a trademark of Maxim Integrated Products, Inc.

Summary of content (11 pages)

PAGE 1
9-2875; Rev 1; 12/03 KIT ATION EVALU E L B A AVAIL High-Efficiency, 40V Step-Up Converters for 2 to 10 White LEDs The MAX1553/MAX1554 drive white LEDs in series with a constant current to provide efficient display backlighting in cellular phones, PDAs, and other hand-held devices. The step-up converter includes an internal 40V, low RDSON, N-channel MOSFET switch for high efficiency and maximum battery life.
PAGE 2
MAX1553/MAX1554 High-Efficiency, 40V Step-Up Converters for 2 to 10 White LEDs ABSOLUTE MAXIMUM RATINGS VCC, FB, OV to GND..............................................-0.3V to +6.0V LX to GND ..............................................................-0.3V to +45V EN, BRT, SS to GND...................................-0.3V to (VCC + 0.3V) ILX ...................................................................................0.
PAGE 3
High-Efficiency, 40V Step-Up Converters for 2 to 10 White LEDs (VCC = 3.3V, VOV = 0V, COUT = 1µF, RSENSE = 10Ω, TA = 0°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER LX Current Limit LX Leakage Current CONDITIONS MIN TYP MAX1553 300 480 600 MAX1554, VCC = 4.2V 600 970 1200 TA = +25°C 0.1 5 TA = +85°C 1 VLX = 38V, VEN = 0V MAX UNITS mA µA SHUTDOWN CONTROL EN Logic-Level High 1.8 V EN Logic-Level Low EN Input Current 0.4 VEN = 0V or 5.
PAGE 4
Typical Operating Characteristics (MAX1553 driving six white LEDs, VCC = VEN = 3.6V, Circuit of Figure 1, TA = +25°C, unless otherwise noted.) VCC = 3.6V 70 VCC = 3V 60 80 VCC = 3.6V VCC = 3V 70 10 15 20 5 EFFICIENCY vs. LOAD CURRENT WITH MAX1554 DRIVING 9 WHITE LEDS L1 = 47µH 4700pF ACROSS LEDs VCC = 4V 80 VCC = 3.6V 70 20 15 0 LED CURRENT vs.
PAGE 5
High-Efficiency, 40V Step-Up Converters for 2 to 10 White LEDs SWITCHING WAVEFORMS (DISCONTINUOUS OPERATION, 3.75V Li+ BATTERY, 10mA OUTPUT) SWITCHING WAVEFORMS (CONTINUOUS OPERATION, 3.
PAGE 6
High-Efficiency, 40V Step-Up Converters for 2 to 10 White LEDs MAX1553/MAX1554 Pin Description PIN NAME FUNCTION 1 GND Ground 2 VCC Voltage-Supply Input. 2.7V to 5.5V. The IC is powered from VCC. 3 EN Enable Input. Drive high or connect to VCC to enable the IC. Drive EN low for shutdown. 4 BRT Brightness-Control Input. Either an analog or PWM control signal can be used. The LED current can be controlled over a 10 to 1 range.
PAGE 7
High-Efficiency, 40V Step-Up Converters for 2 to 10 White LEDs VCC LX ENABLE CONTROL CIRCUITRY EN CONTROL LOGIC DRIVER CURRENT LIMIT GND UVLO VLIM 1.25V BANDGAP REFERENCE REF MINIMUM tOFF ONE-SHOT MINIMUM tON ONE-SHOT BIAS GENERATOR ERROR COMPARATOR FB OV COMPARATOR OV 128kΩ 96kΩ 110kΩ BRT MAX1553 MAX1554 REF 1.25V 67kΩ SS L1 47µH TOKO A920CY-470M 2.7V TO 5.5V INPUT C1 4.7µF ON OFF VCC LX EN OV D1 CMDSH2-3 C2 0.47µF 25V PWM OR DC CONTROL BRT C3 0.1µF SS 2.7V TO 5.
PAGE 8
MAX1553/MAX1554 High-Efficiency, 40V Step-Up Converters for 2 to 10 White LEDs Adjusting the LED Current Adjusting the output current changes the brightness of the LEDs. The LED current is set by the voltage at BRT (VBRT) and the sense resistor (R1) at FB. The V BRT range for adjusting output current is 0 to 1.25V. Over this range, the LED current is found from the following equation: ILED = VBRT + 0.17 6.67 x R1 BRT can be overdriven; however, applying a VBRT greater than 1.
PAGE 9
High-Efficiency, 40V Step-Up Converters for 2 to 10 White LEDs WEBSITE L1 SUPPLIER PHONE Central Semiconductor 631-435-1110 www.centralsemi.com Kamaya 260-489-1533 www.kamaya.com Murata 814-237-1431 www.murata.com Nichia 248-352-6575 www.nichia.com Panasonic 714-373-7939 www.panasonic.com Sumida 847-956-0666 www.sumida.com BRT Taiyo Yuden 408-573-4150 www.t-yuden.com SS TDK 847-803-6100 www.component.tdk.com TOKO 847-297-0070 www.toko.
PAGE 10
Package Information (The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information, go to www.maxim-ic.com/packages. 6, 8, &10L, DFN THIN.EPS MAX1553/MAX1554 High-Efficiency, 40V Step-Up Converters for 2 to 10 White LEDs L A D D2 A2 PIN 1 ID 1 N 1 C0.35 b E PIN 1 INDEX AREA [(N/2)-1] x e REF.
PAGE 11
High-Efficiency, 40V Step-Up Converters for 2 to 10 White LEDs COMMON DIMENSIONS SYMBOL A MIN. MAX. 0.70 0.80 D 2.90 3.10 E 2.90 3.10 A1 0.00 0.05 L k 0.20 0.40 0.25 MIN. A2 0.20 REF. PACKAGE VARIATIONS PKG. CODE N D2 E2 e JEDEC SPEC b T633-1 6 1.50±0.10 2.30±0.10 0.95 BSC MO229 / WEEA 0.40±0.05 1.90 REF T833-1 8 1.50±0.10 2.30±0.10 0.65 BSC MO229 / WEEC 0.30±0.05 1.95 REF T1033-1 10 1.50±0.10 2.30±0.10 0.50 BSC MO229 / WEED-3 0.25±0.05 2.