LX1745 Datasheet, PDF (1/16 Pages) Microsemi Corporation – Triple Output Boost - LED Driver / LCD Bias

INTEGRATED PRODUCTS
LX1745
Triple Output Boost – LED Driver / LCD Bias
PRODUCTION DATASHEET
DESCRIPTION
The LX1745 is a compact high guaranteed at a V_IN equal to 1.6V with
efficiency step-up boost regulator for sustained operation as 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 voltages with an current sense resistor in series with the
additional two integrated boost converters. 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 LX1745 minimizes system cost Depending on the MOSFET selected, the
and condenses layout area making it ideal LX1745 is capable of achieving an LED
for PDA, smart-phone, and digital camera drive in excess of 1.0W.
applications.
The LX1745 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 for LCD Bias generation, the Bias output voltages (up to ±15% typ)
LED driver utilizes an external N-Channel through separate IC interfaces. Each
MOSFET in order to maintain maximum interface has an internal RC filter allowing
efficiency along with flexible power designers to make these adjustments via a
requirements..
direct PWM input signal or an analog
The LX1745’s control circuitry is reference signal. Further, any PWM
optimized for portable systems with a amplitude is easily accommodated using a
shutdown current of less than 1µA. The single external resistor.
input voltage range of 1.6V to 6.0 allows The LX1745 is available in the low-
for a wide selection of system battery profile 20-Pin TSSOP.
voltages
and
start-up
is
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
LX1745
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 Two LCD Bias Voltage
Adjustments Via Analog
Reference Or Direct PWM
Input
ƒ 20-Pin TSSOP Package
APPLICATIONS
ƒ Pagers
ƒ Smart Phones
ƒ PDAs
ƒ Handheld Computers
ƒ General LCD Bias Applications
ƒ LED Driver
LX1745 Evaluation Board
Copyright  2000
Rev. 1.1a, 2004-02-06
PACKAGE ORDER INFO
T_A (°C)
Plastic TSSOP
PW _20-Pin
-40 to 85
LX1745-CPW
Note: Available in Tape & Reel.
Append the letter “T” to the part number.
(i.e. LX1745-CPWT)
Microsemi
Integrated Products Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: [phone]
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