Switcher Drives Lamps In Handhelds

Designed to drive a single cold cathode fluorescent lamp (CCFL) in small handheld equipment displays, the LTC 1697 is a high efficiency 1W switching regulator with internal MOSFETs. The device operates over an input voltage range of 2.8V to 5.5V, allowing it to be powered by a single Li-Ion cell or multicell NiMH/alkaline batteries. Accurate lamp currents can be set with a single external resistor, and an internal PWM dimming frequency is adjustable through a single capacitor. The device uses synchronous current-mode PWM control with its 1A MOSFETs to achieve an efficiency of up to 75%. Its 0.8V reference and internal current sense maintain accurate lamp current, maximizing lamp lifetime. An internal shutdown function reduces supply current to less than 2 µA. The device is mounted in a 10-lead plastic MSOP. Pricing starts at $1.95 each/1,000. LINEAR TECHNOLOGY CORP., Milpitas, CA. (408) 432-1900.