EL Lamp Driver Extends Battery Life Of Portables

With power-saving circuitry and operation from supplies down to 0.9V, the IMP525 electroluminescent lamp driver IC extends the useful operating life of battery-powered portable systems. The single 1.5V cell-powered device is for high-volume backlighting applications in pagers and cellular phones.Four EL lamp driving functions are integrated on the IMP525. These are the boost switchmode power supply, its high-frequency oscillator, the high-voltageH-bridge lamp driver, and the latter's low-frequency oscillator. By boosting a 0.9V to 2.5V dc input voltage to over 100 vac peak-to-peak, an EL lamp is driven by the IC to high brightness. Few external components are required: one inductor, one diode, one capacitor and two resistors. The resistors allow independent adjustment of boost converter frequency and of EL lamp drive frequency. When in disable mode, the IC draws just 2 µA.