HV859

*Absolute Maximum Ratings are those values beyond which damage to the device may occur. Functional operation under these conditions is not implied. Continuous operation of the device at the absolute rating level may affect device reliability. All voltages are referenced to device ground.

The Supertex HV859 is a high voltage driver designed for driving Electroluminescent (EL) lamps of up to 5 square inches. The input supply voltage range is from 1.8V to 5.0V. 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 ±105V. The chip can be enabled/disabled by connecting the resistor on R _SW-OSC to V _DD/ ground.

The HV859 has two internal oscillators, a switching MOSFET, and a high voltage EL lamp driver. The frequency for the switching MOSFET is set by an external resistor connected between the R _SW-OSC pin and the supply pin V_DD. The EL lamp driver frequency is set by an external resistor connected between R _EL-OSC pin and the V_DD pin. An external inductor is connected between the L_X and V_DD pins or V_IN for split supply applications. A 0.003-0.1F capacitor is connected between C_S and ground. The EL lamp is connected between V_A and
V_B.

The HV859 switching MOSFET charges the external inductor and discharges it into the capacitor at C_S. The voltage at C_S will start to increase. Once the voltage at C_S reaches a nominal value of 105V, the switching MOSFET is turned OFF to conserve power. The outputs V_A and V_B are confi gured as an H bridge and are switching in opposite states to achieve ±105V across the EL lamp.