IMP803 Просмотр технического описания (PDF) - IMP, Inc

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Компоненты Описание

производитель

IMP803

High-Voltage EL Lamp Driver

IMP, Inc 

IMP803

Pin Descriptions

Pin Number

1

2

3

4

5

6

Name

VDD

RSW-OSC

CS

LX

GND

VB

7

VA

8

REL-OSC

Function

Positive voltage supply for the IMP803. Inductor L may be connected here or to a

separate unregulated supply.

Switch-mode resistor pin. Switching frequency is determined by an external resistor, RSW.

Boost converter storage capacitor. The voltage across the EL lamp is equal to twice the

voltage at CS.

Connection to flyback inductance, L.

Ground pin.

EL lamp drive. The lamp is connected in a high-voltage bridge circuit with VB providing

the complementary connection to VA. The peak-to-peak AC voltage across the EL lamp is

thus two times VCS.

EL lamp drive. (See above)

The EL lamp oscillator frequency setting pin. The oscillator frequency is controlled

by external resistor REL.

External Components

External Component

Diode

Capacitor CS

Resistor REL

Resistor RSW

Inductor L

Lamp, RCL

Description and Selection Guide

Catch diode. A fast reverse recovery diode, with BV > 100, such as a 1N4148.

This is the high voltage capacitor that stores the inductive energy transferred through the

catch diode. A 100 volt capacitor between 10nF and 100nF is recommended.

The EL lamp oscillator frequency setting resistor. This resistor, connected between the

REL-OSC pin and VDD, provides an oscillator frequency inversely proportional to REL;

as REL increases, the EL lamp frequency decreases along with the current drawn by the lamp.

Lamp color is also determined by this frequency. A 2MΩ resistor between the REL-OSC pin and the

VDD supply results in a lamp frequency around 350Hz: a 1MΩ resistor will give ≈700Hz.

Switching Oscillator frequency setting resistor. The switching oscillator resistor is connected

between the RSW-OSC pin and the VDD supply. The switching frequency is inversely proportional

to the resistor value, dropping as the resistance increases.

The inductor provides the voltage boost needed by means of inductive “flyback”. The internal

MOSFET switch alternately opens and closes the ground connection for the inductor at the

LX pin. When this internal switch opens, the inductor potential will forward-bias the catch

diode and the current will pass through the storage capacitor CS, charging it to a high voltage.

Smaller inductors are preferred to prevent saturation. As the value of the inductor

increases (and the series DC resistance of the inductor decreases), the switching frequency

set by RSW should be increased to prevent saturation. In general, smaller value inductors that

can handle more current are more desirable when larger area EL lamps must be driven.

An external resistor (RCL) in series with the lamp will protect the output drivers from high transient

currents during lamp commutation.

High Voltages Present

The IMP803 generates high voltages and caution should

be exercised.

4

408-432-9100/www.impweb.com

© 2000 IMP, Inc.

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