Device Quietly Drives EL Backlights For Cell Phone LCDs

Feb. 1, 2001

Used for powering electroluminescent (EL) lamps for backlighting LCDs and keypads in cellular phones and other wireless communication devices, the SP4438 driver features clipped-sinusoid waveform, with gradual rising and falling edges, to obtain low acoustic noise. The output waveform, combined with constant current to the lamp and low-frequency operation, also minimizes electromagnetic interference and stress on the lamp to extend lamp lifetime. The SP4438 operates from a 2.7V to 3.3V supply and is designed to drive cell-phone-sized lamps from 1 to 3 sq. in. in size. One external resistor is used to set the internal oscillator frequency, and one inductor is required to generate the high-voltage ac output to drive the EL lamp. The SP4438 also has a standby mode that draws less than 1 µA. And the device is offered in a space-saving 8-pin MSOP package, with all input pins ESD protected with internal diodes to VDD and VSS. The SP4438EU is available starting at $1.07 each/10K.

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