AIC3643

AIC3643 Built-in OVP White LED Step-Up Converter FEATURES Built-In Open Circuit Protection Over Voltage Protection Efficiency Up to 83% at VIN=4.2V, 3LEDs, ILED=20mA 1.2MHz Fixed Switching Frequency Drives Up to 5LEDs in series 2.5V to 5.5V Input Voltage Low Supply Current: 150μA Matches LED Current Requires Tiny Inductor and Capacitors TSOT-23-6, and SOT-23-6 Packages DESCRIPTION AIC3643 is a current-mode pulse-widthmodulation (PWM), step-up DC/DC converter designed to drive white LEDs with a constant current to provide backlight in hand-held devices. Series connection of LEDs provides identical LED currents resulting in uniform brightness. This configuration eliminates the need of ballast resistors. The built-in open load protection prevents the damage resulting from an open circuit condition. Also low 100mV feedback voltage minimizes power loss in the current setting resistor for better efficiency. AIC3643 is a step-up PWM converter, which includes an internal N-channel MOSFET switch for high efficiency. The high switching frequency, 1.2MHz, allows the use of tiny external components. AIC3643 is available in a space-saving TSOT23-6, and SOT-23-6 packages. APPLICATIONS Cellular Phones PDAs DSCs Handheld Devices White LED Display Backlighting TYPICAL APPLICATION CIRCUIT 3.0~4.2V C1 1μF L 6.8μH VIN SW D1 C2 3.3μF Efficiency (%) 90 85 VIN=4.2V VIN=3.6V 80 SHDN OVP GND FB RFB 5Ω 20mA 75 VIN=3V AIC3643 L1: GTSD31-6R8M, GOTREND D1: SS0540, PAN JIT C1: JMK107BJ105KA, TA...