
LX1744
P
RODUCTION
D
ATASHEET
Microsemi
Integrated Products Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 1
W
M
.
C
Dual Output Boost – LED Driver / LCD Bias
I N T E G R A T E D P R O D U C T S
Copyright
2000
Rev. 1.1b, 2005-03-01
D E S C R I P T I O N
The LX1744 is a compact high
efficiency step-up boost regulator for
driving white or color LEDs in LCD
lighting applications while supplying the
necessary LCD bias voltage with an
additional integrated boost converter.
Designed for maximum efficiency and
featuring
a
psuedo-hysteretic
topology (that decreases output voltage
ripple), the LX1744 minimizes system cost
and condenses layout area making it ideal
for PDA, smart-phone, and digital camera
applications.
While the LCD Bias generation is
implemented using an internal N-Channel
MOSFET, the LED driver utilizes an
external N-Channel MOSFET in order to
maintain maximum efficiency along with
flexible power requirements.
The LX1744’s control circuitry is
optimized for portable systems with a
shutdown current of less than 1μA. The
input voltage range of 1.6V to 6.0V allows
for a wide selection of system battery
voltages and start-up is guaranteed at a V
IN
PFM
equal to 1.6V with sustained operation as
low as 1.1V.
The maximum LED drive current is
easily programmed using one external
current sense resistor in series with the
LEDs. In this configuration, LED current
provides a feedback signal to the FB pin,
maintaining constant current regardless of
varying
LED
forward
Depending on the MOSFET selected, the
LX1744 is capable of achieving an LED
drive in excess of 1.0W.
The LX1744 provides simple dynamic
adjustment of the LED drive current (0% to
100% full range dimming) and the LCD
Bias output voltage (up to
±
15% typ)
through separate IC interfaces. Each
interface has an internal RC filter allowing
designers to make these adjustments via a
direct PWM input signal or an analog
reference signal. Further, any PWM
amplitude is easily accommodated using a
single external resistor.
The LX1744 is available in the 14-Pin
TSSOP, and the miniature 16-Pin MLP
requiring minimal PCB area.
voltage
(V
F
).
IMPORTANT:
For the most current data, consult
MICROSEMI
’s website:
http://www.microsemi.com
K E Y F E A T U R E S
> 90% Maximum Efficiency
Low Quiescent Supply Current
Externally Programmable Peak
Inductor Current Limit for
Maximum Efficiency
Logic Controlled Shutdown
< 1μA Shutdown Current
Dynamic Output LED Current
and LCD Bias Voltage
Adjustment via Analog
Reference or Direct PWM Input
14-Pin TSSOP or 16-Pin MLPQ
Package
A P P L I C A T I O N S
Pagers
Smart Phones
PDAs
Handheld Computers
General LCD Bias Applications
LED Driver
P R O D U C T H I G H L I G H T
C
1
4.7μ
F
L
1
47
μ
H
1206 Case Size
LX1744
LFB
CS
DRV
IN
SRC
R
SET
15
V
BAT
= 1.6V to 6.0V
I
LED
= 20mA to 0mA
OVP
SW1
V
LCD1
= V
IN
to 25V
FB1
- V
LCD
BRT
LSHDN
ON OFF
SW2
FB2
V
LCD2
= V
IN
to 25V
REF
ADJ1
SHDN1
ON OFF
GND
ADJ2
SHDN2
ON OFF
LX1744 Evaluation Board
P A C K A G E O R D E R I N F O
Plastic TSSOP
14-Pin
RoHS Compliant / Pb-free
Transition DC: 0442
LX1744CPW
Note: Available in Tape & Reel.
Append the letters “TR” to the part number. (i.e. LX1744CLQ-TR)
PW
LQ
RoHS Compliant / Pb-free
Transition DC: 0430
LX1744CLQ
Plastic MLP-Q
16-Pin
T
A
(
°
C)
-40 to 85
L
X
1
7
4
4