LX1744 Datasheet, PDF (1/16 Pages) Microsemi Corporation – Dual Output Boost - LED Driver / LCD Bias

INTEGRATED PRODUCTS
LX1744
Dual Output Boost – LED Driver / LCD Bias
PRODUCTION DATASHEET
DESCRIPTION
The LX1744 is a compact high equal to 1.6V with sustained operation as
efficiency step-up boost regulator for low as 1.1V.
driving white or color LEDs in LCD The maximum LED drive current is
lighting applications while supplying the easily programmed using one external
necessary LCD bias voltage with an current sense resistor in series with the
additional integrated boost converter.
LEDs. In this configuration, LED current
Designed for maximum efficiency and provides a feedback signal to the FB pin,
featuring a psuedo-hysteretic PFM maintaining constant current regardless of
topology (that decreases output voltage varying LED forward voltage (V_F).
ripple), the LX1744 minimizes system cost Depending on the MOSFET selected, the
and condenses layout area making it ideal LX1744 is capable of achieving an LED
for PDA, smart-phone, and digital camera drive in excess of 1.0W.
applications.
The LX1744 provides simple dynamic
While the LCD Bias generation is adjustment of the LED drive current (0% to
implemented using an internal N-Channel 100% full range dimming) and the LCD
MOSFET, the LED driver utilizes an Bias output voltage (up to ±15% typ)
external N-Channel MOSFET in order to through separate IC interfaces. Each
maintain maximum efficiency along with interface has an internal RC filter allowing
flexible power requirements.
designers to make these adjustments via a
The LX1744’s control circuitry is direct PWM input signal or an analog
optimized for portable systems with a reference signal. Further, any PWM
shutdown current of less than 1µA. The amplitude is easily accommodated using a
input voltage range of 1.6V to 6.0V allows single external resistor.
for a wide selection of system battery The LX1744 is available in the 14-Pin
voltages and start-up is guaranteed at a V_IN TSSOP, and the miniature 16-Pin MLP
requiring minimal PCB area.
IMPORTANT: For the most current data, consult MICROSEMI’s website: http://www.microsemi.com
V_BAT = 1.6V to 6.0V
- V_LCD
V_LCD1 = V_IN to 25V
V_LCD2 = V_IN to 25V
PRODUCT HIGHLIGHT
L₁
47µH
1206 Case Size
IN
SW1
DRV
SRC
OVP
LFB
FB1
CS
LX1744
SW2
REF
LSHDN
BRT
FB2
SHDN1
GND
ADJ1
SHDN2 ADJ2
ON OFF
ON OFF
I_LED = 20mA to 0mA
C₁
4.7µF
R_SET
15Ω
ON OFF
KEY FEATURES
ƒ > 90% Maximum Efficiency
ƒ Low Quiescent Supply Current
ƒ Externally Programmable Peak
Inductor Current Limit for
Maximum Efficiency
ƒ Logic Controlled Shutdown
ƒ < 1µA Shutdown Current
ƒ Dynamic Output LED Current
and LCD Bias Voltage
Adjustment via Analog
Reference or Direct PWM Input
ƒ 14-Pin TSSOP or 16-Pin MLPQ
Package
APPLICATIONS
ƒ Pagers
ƒ Smart Phones
ƒ PDAs
ƒ Handheld Computers
ƒ General LCD Bias Applications
ƒ LED Driver
LX1744 Evaluation Board
Copyright © 2000
Rev. 1.1b, 2005-03-01
T_A (°C)
-40 to 85
PACKAGE ORDER INFO
Plastic TSSOP
Plastic MLP-Q
PW _14-Pin
LQ _16-Pin
RoHS Compliant / Pb-free
Transition DC: 0442
RoHS Compliant / Pb-free
Transition DC: 0430
LX1744CPW
LX1744CLQ
Note: Available in Tape & Reel.
Append the letters “TR” to the part number. (i.e. LX1744CLQ-TR)
Microsemi
Integrated Products Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: [phone]
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