Seiko NPC has started shipping samples of its newly developed SM8146AD electroluminescent (EL) driver IC. Using a sine wave to drive the EL sheet^*1 of a cell phone, the SM8146AD reduces piezoelectric audible noise without the use of an external resistor.

Recent cell phones have continued to add many sophisticated functions. Greater attention has also been paid to the design of the housing, especially with growing demand for a slimmer housing. Traditionally, LEDs have been used for cell phone keypads, but if an EL sheet is used instead, the cell phone not only becomes more compact but also emits a steady light from its keys.

NPC's SM814x series of EL driver ICs, produced using a high-voltage process, can drive the highly efficient and stable EL sheets of mobile systems. The newest member of the series, the SM8146AD has been designed especially with cell phones in mind and incorporates many new features. In an SON-10 package measuring 3.10 mm x 2.85 mm x 0.75 mm, this new driver can drive an EL sheet of up to 30 cm². Because EL driving is done at a constant voltage, the SM8146AD can maintain stable EL luminance unaffected by a battery voltage drop when it is directly driven by a battery such as a lithium-ion battery. In addition, the luminance can be adjusted in eight steps by inputting a pulse, and the input pins (ENA and DIM) can be directly controlled by a 1.8-V CPU, enabling the illumination of the keypad to be easily controlled.

The SM8146AD uses a sine wave for driving an EL sheet to suppress audible noise that would create problems in a mobile terminal with densely packed components. As a result, a smooth sine wave can be used to drive the EL sheet with little noise, and harmonic components can be suppressed. Moreover, the SM8146AD EL driver IC eliminates the need of an external resistor for adjustment, simplifying design.

Manufacturers can use the SM8146AD to create a slim, light-weight cell phone with an EL sheet that provides steady keypad lighting. Also, because audible noise can be reduced without using an external resistor, design time and effort can be reduced and the number of peripheral components can be decreased.

NPC also offers white LED driver ICs, and is planning to add power management ICs to its product line.

*1 EL sheet: Light-emitting element that lights when an AC voltage is applied to its phosphor materials dispersed in a binder with a high dielectric constant.

Name	Sample shipment date	Price with and without tax	Volume production date	Planned production
SM8146AD	August 2006	150 yen/unit (157 yen/unit)	September 2006	1.5 million units/month