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Maxim Integrated Semiconductor Electronic Components Datasheet

MAX1848 Datasheet

White LED Step-Up Converter in SOT23

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MAX1848 pdf
19-2028; Rev 1; 9/02
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 RDSON N-channel MOSFET switch for high
efficiency and maximum battery life. A single analog
voltage Dual Modeinput 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
Typical Application Circuit
Features
o Constant Current Regulation for Uniform
Illumination
o High 87% Efficiency
o Analog or Logic Control of LED Intensity
o 0.8W Output Power with Internal High-Voltage
MOSFET Switch
o Small, Low-Profile External Components
o 2.6V to 5.5V Input Range
o 13V Maximum Output with Overvoltage Protection
o Optimized for Low Input Ripple
o Programmable Soft-Start
o 0.3µA Shutdown Current
o Small 8-pin Thin QFN (3mm 3mm) and
8-Pin SOT23 Packages
Ordering Information
PART
TEMP RANGE PIN-PACKAGE
TOP
MARK
MAX1848EKA
MAX1848ETA
-40°C to +85°C
-40°C to +85°C
8 SOT23
8 Thin QFN
(3mm 3mm)
AAIM
ACR
Note: Hand soldering is not recommended for the MAX1848
SOT23 package.
Pin Configuration
2.6V to 5.5V
CIN
3.3µF
LOGIC
OR DAC
CCOMP
0.15µF
L1
33µH
LX
V+ OUT
MAX1848
PGND
CTRL
GND
D1
COUT
1µF
COMP
CS
RSENSE
5
TOP VIEW
COMP 1
CTRL 2
OUT 3
LX 4
MAX1848
8 V+
COMP 1
7 CS
CTRL 2
6 GND
OUT 3
5 PGND
LX 4
MAX1848
8 V+
7 CS
6 GND
5 PGND
SOT23
THIN QFN
3mm x 3mm
Dual Mode is a trademark of Maxim Integrated Products, Inc.
________________________________________________________________ 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.


Maxim Integrated Semiconductor Electronic Components Datasheet

MAX1848 Datasheet

White LED Step-Up Converter in SOT23

No Preview Available !

MAX1848 pdf
White LED Step-Up Converter in SOT23
ABSOLUTE MAXIMUM RATINGS
V+ to GND ................................................................-0.3V to +6V
PGND to GND .......................................................-0.3V to +0.3V
LX, OUT to GND .....................................................-0.3V to +14V
LX to OUT ...............................................................-14V to +0.3V
CTRL to GND.......................................-0.3V to +6V or (V+ + 2V)
COMP, CS to GND .......................................-0.3V to (V+ + 0.3V)
LX Current ....................................................................0.45ARMS
Continuous Power Dissipation (TA = +70°C)
8-Pin SOT23 (derate 9.7mW/°C above +70°C).............777mW
8-Pin Thin QFN 3mm 3mm (derate 24.4mW/°C
above +70°C)..............................................................1951mW
Operating Temperature Range ...........................-40°C to +85°C
Junction Temperature ......................................................+150°C
Storage Temperature Range .............................-60°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
DC ELECTRICAL CHARACTERISTICS
(V+ = 3V, VOUT = 11V, L = 33µH, COUT = 1µF, CCOMP = 0.15µF, RSENSE = 5, VCTRL = 1V, TA = 0°C to +85°C, unless otherwise
noted. Typical values are at TA = +25°C.)
PARAMETER
Supply Voltage
Undervoltage Lockout Threshold
Quiescent Current
Shutdown Supply Current
Overvoltage Threshold
OUT Input Bias Current
Output Voltage Range
ERROR AMPLIFIER
CTRL to CS Regulation
CS Input Bias Current
CTRL Input Resistance
CTRL Dual Mode Threshold
CS Line Regulation
COMP Pin Resistance to Ground
COMP Output Voltage Swing
OSCILLATOR
Operating Frequency
Minimum Duty Cycle
Maximum Duty Cycle
CONDITIONS
V+ rising, 40mV hysteresis typical
V+ falling
Not switching, VCTRL = VCS = V+
Switching, VCTRL = V+, VCS = GND
VCTRL = GND
TA = +25°C
TA = +85°C
V+ rising, 1V hysteresis typical
V+ falling
VOUT = 13V
VCTRL > 0.25V
VCTRL = GND
VCTRL = 2V, V+ = 2.6V to 5.5V
VCS = VCTRL /13.33
Hysteresis = 25mV typical
V+ = 2.6V to 5.5V, VCTRL = 3V
Device in shutdown or overvoltage
PWM mode
Pulse skipping
VCTRL = V+, VCS = GND
MIN
2.6
2.15
2.10
12.5
11.5
10
V+ -
VDIODE
TYP
2.38
2.34
0.25
1
0.3
0.3
13.25
12.25
20
0.01
MAX
5.5
2.59
2.56
0.40
2
1
14.0
13
30
1
12.5
UNITS
V
V
mA
µA
V
µA
V
71 75 81 mV/V
0.01 1
µA
450 670 1100 k
100 170 240
mV
0.05 %/V
7.5 15 50 k
0.3 2.4 V
1.0 1.2 1.5 MHz
12
%
0
85 90 97
%
2 _______________________________________________________________________________________


Part Number MAX1848
Description White LED Step-Up Converter in SOT23
Maker Maxim
Total Page 9 Pages
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