Supertex inc.

Supertex inc.

www.supertex.com

HV857

Doc.# DSFP-HV857

A062013

Features

frequencies

Applications

General Description

The Supertex HV857 is a high voltage driver designed for driving

Electroluminescent (EL) lamps of up to 5.0 square inches. The

input supply voltage range is from 1.8 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 ±95V. The chip can be enabled/disabled by connecting the

resistor on RSW-Osc to VDD/GND.

The HV857 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 RSW-Osc pin and the supply pin VDD. The EL lamp driver

frequency is set by an external resistor connected between REL-

Osc pin and VDD pin. An external inductor is connected between

the LX and VDD pins or V

0.1µF capacitor is connected between CS and ground. The EL

lamp is connected between VA and VB.

The switching MOSFET charges the external inductor and

discharges it into the capacitor at CS. 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. The

outputs VA and VB are configured as an H bridge and are switching

in opposite states to achieve ±95V across the EL lamp.

Typical Application Circuit

Low Noise, High Voltage

EL Lamp Driver IC

EL Lamp

+

_

C

S

V

IN

L

X

C

IN

Enable Signal

ON = V

DD

OFF = 0

D

+

_

V

DD

C

DD

R

SW

R

EL

1

2

3

4

8

7

6

5

VDD

RSW-Osc

REL-Osc

GND

VA

VB

CS

LX

HV857