The Supertex HV839 is a high voltage driver designed for driving two EL lamps with a combined area of 3.5 square inches. The input supply voltage range is from 2.0V to 5.8V. The device is designed to reduce the amount of audible noise emitted by the lamp. This device uses a single inductor and minimum number of passive components to drive two EL lamps. The nominal regulated output voltage of 90V is applied to the EL lamps. The two EL lamps can be turned ON and OFF by the two logic input control pins, C1 and C2. The device is disabled when both C1 and C2 (pins 1 and 4) are at logic low. The HV839 has an internal oscillator, a switching MOSFET, and two high voltage EL lamp drivers. An external resistor connected between the RSW-OSC pin and the voltage supply pin VDD sets the frequency for the switching MOSFET. The EL lamp driver frequency is set by dividing the MOSFET switching frequency by 128. An external inductor is connected between the LX and the VDD pins. Depending on the EL lamp size, a 1.0 to 10.0nF, 100V capacitor is connected between CS and Ground. The two EL lamps are connected between EL1 to Com and EL2 to Com. The switching MOSFET charges the external inductor and discharges it into the capacitor at CS. The voltage at CS increases. Once the voltage at CS reaches a nominal value of 90V, the switching MOSFET is turned OFF to conserve power. The outputs EL1 to Com and EL2 to Com are configured as H bridges and switch in opposite states to achieve 180V across the EL lamp.