LT3474-1

The LT^®3474/LT3474-1 are fi xed frequency step-down DC/DC converters designed to operate as constant-current sources. An internal sense resistor monitors the output current allowing accurate current regulation, ideal for driving high current LEDs. High output current accuracy is maintained over a wide current range, from 35mA to 1A, allowing a wide dimming range.

Unique PWM circuitry allows a dimming range of 400:1, avoiding the color shift normally associated with LED current dimming.

The high switching frequency of LT3474/LT3474-1offers several advantages, permitting the use of small inductors and ceramic capacitors.

Small inductors combined with the 16-lead TSSOP surface mount package save space and cost versus alternative solutions. The constant switching frequency combined with low-impedance ceramic capacitors result in low, predictable output ripple.

With their wide input range of 4V to 36V, the LT3474/ LT3474-1 regulate a broad array of power sources, from 5V logic rails to unregulated wall transformers, lead acid batteries and distributed power supplies. A current mode PWM architecture provides fast transient response and cycle-by-cycle current limiting. Frequency foldback and thermal shutdown provide additional protection.