SC4540ULTRT Semtech

SC4540 High Effi ciency Boost Converter for up to 10 LEDs POWER MANAGEMENT Features Description Input voltage range 4.5V to 12V The SC4540 is designed to regulate current for a series Programmable LED current up to 30mA string of white LEDs in LCD backlighting applications Current-mode PWM control 800kHz where small size and high effi ciency are priorities. This Soft-start to reduce in-rush current device integrates an 800kHz current-mode PWM boost PWM dimming 100Hz to 50kHz converter and a 30mA programmable low dropout current PWM dimming at ISET analog and fi ltered sink regulator. The wide input voltage range of the SC4540 Over-voltage protection 38V (minimum) makes it ideal for use with dual-cell Li-ion powered Under-voltage lockout (UVLO) applications. Thermal shutdown An external resistor sets the LED current up to 30mA. Shutdown current <0.1A (typical) PWM dimming (100Hz to 50kHz) may be applied directly Ultra-thin package 2 x 2 x 0.6 (mm) to the enable (EN) pin, or dimming can be controlled by Lead-free package, WEEE and RoHS compliant applying an analog signal to the ISET circuit. The boost circuit can output up to 38V (guaranteed) to drive up to 10 LEDs in series. The current regulator protects against Applications shorts between the BL and OUT pins and also eliminates DSLR, DSC, and Video Cameras backlight glow during shutdown when using LEDs with Portable media players high leakage. Under-voltage lockout and thermal shut- Set-top boxes down provide additional protection. A small external Personal navigation devices capacitor and series resistor control soft-start and loop compensation. Over-voltage detection protects the SC4540 if the BL pin is fl oating or shorted to ground. The SC4540 is available in an MLPD-8 pin 2 x 2 x 0.6 (mm) package, with a rated temperature range of -40C to +85C. Typical Application Circuit D L1 1 F 56 H LX C OUT 4.5 to 12V IN OUT C IN 2.2 F SC4540 E nable and EN PW M dimming R IS E T ISET C COMP R COMP COMP 1.27k 47nF BL GND July 18, 2008 2008 Semtech Corporation 1SC4540 Pin Confi guration Ordering Information Device Package (1) (2) SC4540ULTRT MLPD-UT-8 2x2 SC4540EVB Evaluation Board Note: LX 1 8 IN (1) Available in tape and reel only. A reel contains 3,000 devices. TOP (2) Lead-free package only. Device is WEEE and RoHS compliant. VIEW 2 7 EN GND ISET 3 6 BL 4 5 OUT COMP T MLPD: 2mm x 2mm 8 Lead = 74C/W JA Marking Information FJ0 yw FJ0 = Marking code for SC4540 yw = Date Code 2