IMP525ESA datasheet(4/8 Pages) IMP

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IMP525

Pin Descriptions

Pin Number

Name

Function

VDD

Positive voltage supply for the IMP525. Inductor L may be connected here or to a

separate supply.

RSW-OSC

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

connected between pin 2 and VDD.

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

voltage at CS.

Connection to flyback inductance, L.

GND

Ground pin.

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

the complementary connection to VA.

EL lamp drive. (See above)

REL-OSC

The EL lamp oscillator frequency-setting pin. The frequency is controlled by resistor REL,

connected from pin 8 to VDD.

Disable Pad

DIS

Available only in die form. Setting DIS HIGH disables the chip.

External Component

Description and Selection Guide

Diode

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

Capacitor CS

The high voltage capacitor that stores the inductive energy transferred through the

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

Resistor REL

The EL lamp oscillator frequency-setting resistor. REL is connected between pin 8 and VDD,

providing a 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 1M

Ω resistor between the R

EL-OSC pin and the VDD supply results in a lamp

frequency around 500Hz.

Resistor RSW

Switching Oscillator frequency-setting resistor. RSW 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.

Capacitor CSW

This is an optional noise-suppression capacitor connected from ground to the RSW-OSC pin.

A 100pF capacitor is recommended.

Inductor L

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 the switch opens, the inductor potential will forward-bias the diode

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

As the value of the inductor is increased, the switching frequency set by RSW should also 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.

A small electrolytic capacitor (10

µF, 16V), normally present across the inductor supply V

IN,

will likely eliminate the need for CSW.

External Components

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