19-2028; Rev 2; 8/05
White LED Step-Up Converter in SOT23
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.
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
Ordering Information
Applications
Cell Phones and Smart Phones
PDAs, Palmtops, and Wireless Handhelds
e-Books and Subnotebooks
White LED Display Backlighting
PART
MAX1848EKA-T
MAX1848ETA-T
MAX1848ETA+T
TEMP RANGE
-40 ° C to +85 ° C
-40 ° C to +85 ° C
-40 ° C to +85 ° C
PIN-
PACKAGE
8 SOT23
8 Thin QFN
(3mm ? 3mm)
8 Thin QFN
(3mm ? 3mm)
TOP
MARK
AAIM
ACR
ACR
+ Denotes lead-free package.
Note: Hand soldering is not recommended for the MAX1848
SOT23 package.
Typical Application Circuit
L1
Pin Configuration
2.6V to 5.5V
33 μ H
TOP VIEW
C IN
3.3 μ F
V+
MAX1848
LX
OUT
D1
C OUT
1 μ F
COMP
CTRL
OUT
1
2
3
+
MAX1848
8
7
6
V+
CS
GND
COMP
CTRL
OUT
1
2
3
+
MAX1848
8
7
6
V+
CS
GND
LOGIC
OR DAC
CTRL
PGND
GND
LX 4
5
PGND
LX
4
5
PGND
SOT23
THIN QFN
C COMP
0.15 μ F
COMP
CS
3mm x 3mm
R SENSE
5 Ω
Dual Mode is a trademark of Maxim Integrated Products, Inc.
________________________________________________________________ Maxim Integrated Products
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
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MAX1848EVKIT 功能描述:LED 照明开发工具 Evaluation Kit for the MAX1848 RoHS:否 制造商:Fairchild Semiconductor 产品:Evaluation Kits 用于:FL7732 核心: 电源电压:120V 系列: 封装:
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