The Supertex HV858 is a high voltage triple EL lamp driver designed for driving combined EL lamps of up to 3.0 in2 (1.0 in2 each). The input supply voltage range is from 1.8V to 6.5V. The device is designed such that the input voltage to the inductor can be different from the input voltage to the device (split supply). The device uses a single inductor and a minimum number of passive components. The nominal regulated output voltage that is applied to the EL lamp is 95V. The HV858 has two internal oscillators, one for the internal switching MOSFET, and the other for the high voltage EL lamp driver. The EL lamp frequency is fixed internally at 500Hz. The power converter oscillator runs 256 times faster than the EL lamp driver at 128kHz. An external inductor is connected between the LX and VDD pins (or between the LX pin and separate voltage source in the case of a split supply application). A 0.002-0.01F, 100V capacitor is connected between the Cs pin and ground. The switching MOSFET charges the external inductor and discharges it into the capacitor at the Cs pin. The voltage at Cs will start to increase. Once the voltage at Cs reaches a nominal value of 95V, the switching MOSFET is turned OFF to conserve power.