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HV857

11/14/01

Supertex Inc. does not recommend the use of its products in life support applications and will not knowingly sell its products for use in such applications unless it receives an adequate "products liability

indemnification insurance agreement." Supertex does not assume responsibility for use of devices described and limits its liability to the replacement of devices determined to be defective due to

workmanship. No responsibility is assumed for possible omissions or inaccuracies. Circuitry and specifications are subject to change without notice. For the latest product specifications, refer to the

Supertex website: http://www.supertex.com. For complete liability information on all Supertex products, refer to the most current databook or to the Legal/Disclaimer page on the Supertex website.

HV857

High Voltage EL Lamp Driver for

Low Noise Applications

Features

❏ Patent pending audible noise reduction

❏ Patent pending lamp aging compensation

❏ 190V

❏ Patented output timing for high efficiency

❏ Single cell lithium ion compatible

❏ 150nA shutdown current

❏ Wide input voltage range 1.8V to 5.0V

❏ Separately adjustable lamp and converter frequencies

❏ Output voltage regulation

❏ Split supply capability

Applications

❏ LCD backlighting

❏ Mobile cellular phones

❏ PDAs

❏ Handheld wireless communication products

❏ Global Positioning Systems (GPS)

General Description

The Supertex HV857 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

the resistor on R

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 R

driver frequency is set by an external resistor connected be-

tween R

connected between the L

and ground. The EL lamp is connected between V

The switching MOSFET charges the external inductor and

discharges it into the capacitor at C

to increase. Once the voltage at C

95V, the switching MOSFET is turned OFF to conserve power.

The outputs V

switching in opposite states to achieve

Typical Application

EL Lamp

+

_

1

2

3

4

8

6

5

HV857MG

7

Gnd

Enable Signal

OFF=0