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.
2.5V to 15V Input Voltage Range
Up to 700mAoutput current
Typical efficiency# >80%
User-defined thermal control of LED output current using external thermistor
High output current stability over input voltage and temperature