Electronic Design

Compact High-Efficiency EL Lamp Driver Targets PDAs

The SP4403 lamp driver for backlighting electroluminescent (EL) displays suits personal digital assistants. It offers a small form factor, high efficiency, and sufficient drive for a bright output from EL display lamps. Its high coil-switching frequency facilitates the use of 470-µH inductors that are less than 2 mm high. The inductor typically switches at 51.2 kHz with a 90% duty cycle and a maximum peak coil current of 75 mA.

Additionally, the SP4403's resistor-controlled oscillator design delivers narrow lamp frequency distributions, as well as tight performance between -40°C and 85°C. An 8-pin µSOIC package minimizes board-space requirements, and a low-power standby mode draws only 50 nA, typically, and 1 µA maximum in the shutdown mode.

The SP4403 operates from a battery voltage of 2.2 to 4.5 V at a typical, 38-mA supply current. This dc-ac inverter also produces up to 220 V p-p ac (210 V ac typical) when driving an EL display panel operating at a typical frequency of 400 Hz. It's manufactured on a dielectrically isolated biCMOS process.

The SP4405, a pin-compatible version of the SP4403, includes a regulated output voltage that maintains constant brightness over the battery's life.

Currently available, the SP4403 costs $0.87 each in 10,000-unit quantities. Samples are available from stock. Data sheets and additional information can be found at www.sipex.com/newproducts.

Sipex Corp., 22 Linnell Circle, Billerica, MA 01821; (978) 667-8700; fax (978) 670-9001; www.sipex.com.

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