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General Description

The MAX1848 drives white LEDs with a constant cur-

rent to provide backlight in cell phones, PDAs, and

other hand-held devices. The step-up converter topology

allows series connection of the white LEDs so that the

LED currents are identical for uniform brightness. This

configuration eliminates the need for ballast resistors

and expensive factory calibration. Other benefits

include greater simplicity, lower cost, higher efficiency,

and greater reliability.

This step-up PWM converter includes an internal, high-

voltage, low R

DSON

N-channel MOSFET switch for high

efficiency and maximum battery life. A single analog

voltage Dual Mode

™

input provides a simple means of

brightness adjustment and on/off control. Fast 1.2MHz

current-mode PWM control allows for small input and

output capacitors and a small inductor while minimizing

ripple on the input supply/battery. Programmable soft-

start eliminates inrush current during startup.

The MAX1848 is available in space-saving 8-pin thin

QFN (3mm

3mm) and 8-pin SOT23 packages.

Applications

Cell Phones and Smart Phones

PDAs, Palmtops, and Wireless Handhelds

e-Books and Subnotebooks

White LED Display Backlighting

Features

♦ Constant Current Regulation for Uniform

Illumination

♦ High 87% Efficiency

♦ Analog or Logic Control of LED Intensity

♦ 0.8W Output Power with Internal High-Voltage

MOSFET Switch

♦ Small, Low-Profile External Components

♦ 2.6V to 5.5V Input Range

♦ 13V Maximum Output with Overvoltage Protection

♦ Optimized for Low Input Ripple

♦ Programmable Soft-Start

♦ 0.3µA Shutdown Current

♦ Small 8-pin Thin QFN (3mm

3mm) and

8-Pin SOT23 Packages

MAX1848

White LED Step-Up Converter in SOT23

________________________________________________________________ Maxim Integrated Products 1

GND

PGNDLX

V+

CSCTRL

OUT

COMP

SOT23

TOP VIEW

MAX1848

GND

PGNDLX

V+

CSCTRL

OUT

COMP

THIN QFN

3mm x 3mm

MAX1848

Pin Configuration

Ordering Information

V+

CTRL

COMP

OUT

PGND

GND

2.6V to 5.5V

LOGIC

OR DAC

3.3µF

COMP

0.15µF

33µH

OUT

1µF

SENSE

5Ω

MAX1848

Typical Application Circuit

19-2028; Rev 1; 9/02

PART TEMP RANGE PIN-PACKAGE

TOP

MARK

MAX1848EKA -40°C to +85°C 8 SOT23 AAIM

MAX1848ETA -40°C to +85°C

8 Thin QFN

(3mm

3mm)

ACR

Note: Hand soldering is not recommended for the MAX1848

SOT23 package.

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

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.

1 2 3 4 5 6 7 8 9

Indice de contenidos

Pagina 1

General DescriptionThe MAX1848 drives white LEDs with a constant cur-rent to provide backlight in cell phones, PDAs, andother hand-held devices. The s

Pagina 2 - DC ELECTRICAL CHARACTERISTICS

MAX1848White LED Step-Up Converter in SOT232 _______________________________________________________________________________________ABSOLUTE MAXIMUM R

Pagina 3

MAX1848White LED Step-Up Converter in SOT23_______________________________________________________________________________________ 3DC ELECTRICAL CHAR

Pagina 4 - MAX1848 toc02

MAX1848White LED Step-Up Converter in SOT234 _______________________________________________________________________________________Typical Operating

Pagina 5 - Pin Description

MAX1848White LED Step-Up Converter in SOT23_______________________________________________________________________________________ 520ms/divVCTRL TRAN

Pagina 6 - Design Procedure

MAX1848Detailed DescriptionThe MAX1848’s high efficiency and small size make itideally suited to drive series-connected LEDs. It oper-ates as a boost

Pagina 7 - Chip Information

The output current and the number of LEDs in each legaffect the capacitance of CCOMP. Table 1 shows theminimum CCOMPvalues needed to stabilize the con

Pagina 8 - Package Information

SOT23, 8L.EPSMAX1848White LED Step-Up Converter in SOT238 _______________________________________________________________________________________Packa

Pagina 9 - 6, 8, &10L, QFN THIN.EPS

MAX1848White LED Step-Up Converter in SOT23Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Max

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