IMP522

IMP522

4

408-432-9100/www.impweb.com

© 2001 IMP, Inc.

Application Information

EL Lamp Drive

and ground on alternate phases, creating peak-to-peak signals

across the EL lamps of twice the regulated voltage.

EL Lamp Selection: LMPSEL

The digital input pin LMPSEL allows either or both EL lamps to

be active. Lamp A is active when LMPSEL is LOW and lamp B is

active when LMPSEL is HIGH. When LMPSEL is left floating or

driven by a three-state driver in the high impedance state, both

lamp driver outputs are active.

when the output impedance of the driving voltage signal source

is infinite (driver in OFF state).

Both drivers are OFF if the IMP522 is disabled.

L

E

S

P

M

L

l

a

n

g

i

S

e

v

i

r

D

A

p

m

a

L

d

n

A

e

v

i

r

D

B

p

m

a

L

d

n

A

H

G

I

HF

F

ON

O

W

O

LN

OF

F

O

/

g

n

i

t

a

o

l

F

e

c

n

a

d

e

p

m

I

h

g

i

H

N

ON

O

s

p

e

.

2

0

t

_

2

2

5

EL Driver Output Overvoltage Regulator

120V. The internal overvoltage regulator skips the inductor

tion threshold. The internal overvoltage detection trip point has a

hysterisis of 1V and a range of 110V to 120V at room temperature.

PWM Circuit Switching

The switching MOSFET is driven by the PWM signal (nominally

61kHz). During the first 88% of the period, the switch is ON,

providing a low impedance path (<8

causes the external inductor to charge. In the last 12% of the

period, the MOSFET is turned OFF. This causes the voltage on

forward-bias the external diode, thus pumping charge into the

between 110V and 120V. When the internal regulation trip-point is

reached, the overvoltage regulator turns the MOSFET switch OFF

to conserve power.