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A011706

Tri-EL Lamp Driver IC

Features

Tri-EL lamp driver with common terminal

Independent brightness control for all 3 lamps

1.8V to 6.5V Operating Supply Voltage

Output voltage regulation

Two-pin serial data communication for control

Linear brightness control with seven steps at constant

efficiency

128kHz Fixed Switching Frequency

Split supply capability

Patented high efficiency EL lamp driver

Single miniature inductor drives all 3 lamps

Only 4 external components

Burst mode power converter for best efficiency

CMOS compatible serial interface with noise rejection

150nA max. leakage current when disabled

Power-on reset causes all outputs to be off when first

powered up

Small 10-pin MSOP package

10-pin DFN/MLP package (0.8mm thickness)

Applications

Mulit-segment, variable displays

Cell phone keypads and displays

MP3 players

Watches

General Description

The Supertex HV858 is a high voltage triple EL lamp driver

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 L

pins (or between the L

the case of a split supply application). A 0.002-0.01µF, 100V

capacitor is connected between the C

The switching MOSFET charges the external inductor and

discharges it into the capacitor at the C

C

nominal value of 95V, the switching MOSFET is turned OFF

to conserve power.

One side of the 3 EL lamps is connected to the Com pin of

HV858 and the other side to the EL1, EL2, and EL3 pins of the

HV858. Each EL lamp output may be independently controlled

to have one of the 7 brightness levels or can be completely

turned OFF by a 10-bit serial data input register. The 10-bit

control code has 3 bits to control the brightness level of each

EL Lamp and one bit to optionally control the power converter.

The 3-bit binary brightness control code controls the number

of 500Hz cycles (from 0 to 7) in a group of 7 cycles.

Typical Application Circuit

+

-

D

+

-

EL Lamp 1

7

8

9

10

6

EL Lamp 2

EL Lamp 3

HV858

Clock

Serial Data in

1

2

3

4

5

Com

EL2

EL1

EL3

GND

SDI

SCK

Supertex inc.

HV858

Supertex inc.

A011706