Features: > 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 PackageApplication Pagers
Smart Phones
PDAs
Handheld Computers
General LCD Bias Applications
LED DriverPinout
SpecificationsSupply Input Voltage ...........................................................................-0.3V to 7V
Feedback Input Voltage (VFB, VLFB).......................................-0.3V to VIN + 0.3V
Shutdown Input Voltage (VSHDN , VLSHDN)) ...........................-0.3V to VIN + 0.3V
PWM Input Amplitude (ADJ, BRT).......................................-0.3V to VIN + 0.3V
Analog Adjust Input Voltage (VADJ, VBRT) .............................-0.3V to VIN + 0.3V
SRC Input Current ................................................................................ 800mARMS
Operating Temperature Range.........................................................-40°C to 85°C
Maximum Operating Junction Temperature ................................................ 150°C
Storage Temperature Range...........................................................-65°C to 150°C
RoHS Peak Package Solder Reflow Temperature
(40 second maximum exposure) ..................................................... 260°C (+0, -5)
Note: Exceeding these ratings could cause damage to the device. All voltages are with respect to
Ground. Currents are positive into, negative out of specified terminal.
DescriptionThe 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 PFM topology (that decreases output voltage ripple), the LX 1744 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 VIN 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 voltage (VF). 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 direct PWM input signal or an analog reference signal. Further, any PWM amplitude is easily accommodated using single external resistor.
The LX1744 is available in the 14-Pin TSSOP, and the miniature 16-Pin MLP requiring minimal PCB area.
LX1744 Data Sheet
