Driver family meets demands of next generation LEDs

11th February 2008

ES Admin

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A family of three flexible LED Drivers from Zetex Semiconductors provides designers with the performance needed by the next generation of high brightness LEDs. The ZXLD132X inductive DC-DC converter series drive single or multiple LEDs with currents from 700mA through to 1.5A, in buck, boost and buck/boost configurations. Housed in a tiny 3mm x 4mm DFN package, the drivers can reduce the circuit footprint of existing solutions by up to 50%.

Employing an innovative variable ‘on’ and ‘off’ time control scheme with an adjustable peak switch current limit, the chips are significantly simpler to control than alternative PFM solutions. The drivers also enable both LED current and peak inductor current to be set accurately and independently.

The ZXLD132X feedback control circuit ensures excellent load and current regulation, resulting in LED current stability of typically +/-3% throughout the useful life of the battery and over the extended operating temperature range of –40ºC to 125ºC. LED current can be adjusted from 100% down to 10% of preset value by applying a DC voltage signal and down to 2% using a PWM input.

The highly integrated ZXLD132X LED driver family also features a thermal control circuit that monitors an external thermistor in order to linearly reduce output current once temperature exceeds a predetermined threshold. The device can also be shut down by applying a low-level DC voltage signal.

Patrick Durand, Worldwide Applications Manager for Future Lighting Solutions said, “The next generation of high brightness LEDs, such as Luxeon® K2, require harder driving in order to maximise lumen output. These latest LED drivers from Zetex give designers the output current performance and importantly the ease of use that they’ve been waiting for.”

Chris Jolly, VP Marketing, Zetex Semiconductors added, “By combining the DC-DC converter, a current monitor for accurately stabilising the output current, the thermal control circuitry and a powerful 2A NPN switching transistor into a tiny DFN package, we have enabled our customers to maximise the Lumen output they get from the latest LED technology.”

At the head of the product family, the ZXLD1320 buck mode driver will deliver up to 1.5A continuous LED current for an input voltage range of 4V to 18V. Providing up to a maximum of 24W of power, depending on supply voltage and external component selection, the device will suit halogen lamp replacement and battery driven applications.

The ZXLD1321 is a boost mode driver operating with an input voltage range of 1V to 12V and delivers an LED current of 1A, while the ZXLD1322 is a buck/boost mode driver producing 700mA for an input voltage of 2.5V to 15V. Both devices suit high power LED flashlight, LED back-up lighting and general LED driving applications.