A Product Line of Diodes Incorporated ZXLD1322 BUCK/BOOST MODE DC-DC CONVERTER FOR LED DRIVING WITH 700mA OUTPUT AND CURRENT CONTROL Description The ZXLD1322 is an inductive DC-DC converter, with an internal switch, designed for driving single or multiple LEDs in series up to a total of 700mA output current. Applications cover input voltages ranging from 2.5V to 15V. Depending upon supply voltage and external components, this can provide up to 12W of output power. The device employs a variable on and off time control scheme with adjustable peak switch current limiting and operates in Buck/Boost mode, offering higher power efficiency and lower system cost than conventional PFM buck/boost circuitry. The device includes the DC-DC converter, a high-side current monitor and an NPN switching transistor to provide an integrated solution offering small PCB size, competitive cost/performance, high power efficiency of DC-DC conversion and maximum LED brightness/reliability. More importantly, it retains design flexibility to add customer specific features. The feedback control circuitry inside the ZXLD1322 provides excellent load and current regulation, resulting in very stable LED current over the useful life of the battery and over the full operating temperature range. The LED current can be adjusted from 100% down to 10% of the set value by applying a dc voltage to the ADJ pin and down to 1% by applying a PWM signal. An on-chip LED protection circuit also allows output current to be reduced linearly above a predetermined threshold temperature using an external thermistor at the TADJ pin. External resistors set nominal average LED current and coil peak current independently. The device can be shut down by applying a continuous low level dc voltage to the ADJ pin. Features Pin Assignments 2.5V to 15V Input Voltage Range Up to 700mA output current Typical efficiency >80% User-defined thermal control of LED output current using external thermistor High output current stability over input voltage and temperature 12A typical standby current LED current adjustable from 100% down to 2% Adjustable Soft-Start (Top View) Capable of driving 3 LEDs in series DFN4030-14 with Exposed Pad Applications 4mm x 3mm High power LED flashlights 0.50mm pitch LED back-up lighting 1.5W T = 70C A General LED lighting Typical Application Circuit DFN4030-14 Package(Bottom View) 45 chamfer denote Pin 1 Notes: . Using standard external components as specified under electrical characteristics. Efficiency is dependent upon external component types and values. Higher efficiency is possible with alternative coils. 1 of 17 April 2010 ZXLD1322 Diodes Incorporated www.diodes.com Document number: DS32166 Rev. 3 - 2 A Product Line of Diodes Incorporated ZXLD1322 Block Diagram 2 of 17 April 2010 ZXLD1322 Diodes Incorporated www.diodes.com Document number: DS32166 Rev. 3 - 2