SP4405EN 查看數據表（PDF） - Signal Processing Technologies

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SP4405EN

Low Voltage Electroluminescent Lamp Driver with Regulated Output Voltage

Signal Processing Technologies 

DESCRIPTION

The SP4405 Electroluminescent Lamp Driver

is a low-cost low voltage device ideal for the

replacement of LED backlighting designs in

keypads, handsets, PDAs and other portable

designs. The SP4405 contains a DC-AC inverter

that

can

produce

an

AC

output

of

160V

PP

(typical)

from a +2.2V to +4.5V input voltage. An

internal feedback loop regulates the lamp voltage

output to 160V (typical) with varying supply

PP

voltages to maintain constant EL lamp

brightness. An internal block diagram of the

SP4405 can be found in Figure 1.

The SP4405 is built on Sipex's dielectrically

isolated BiCMOS process that provides the

isolation required to separate the high voltage

AC signal used to drive the EL lamp from the

low voltage logic and signal processing circuitry.

This ensures latch-up free operation in the

interface between the low voltage CMOS

circuitry and the high voltage bipolar circuitry.

A total of only six external components are

required for the standard operation of the

SP4405: an inductor, a fast recovery diode,

three capacitors and a resistor. A diagram of the

SP4405 in a typical application can be found in

Figure 2.

Electroluminescent Technology

An EL lamp is basically a strip of plastic that is

coated with a phosphorous material which emits

light (fluoresces) when a high voltage (>40V)

which was first applied across it, is removed or

reversed. Long periods of DC voltages applied

to the material tend to breakdown the material

VREF=1.25V

SP4405

ROSC

450kΩ

VDD 6

ROSC 8 OSC

C1

C2

0.1µF

1nF

ERROR

COMPARATOR

Q

FF7

Q

2

VSS

1

ELEN

fCOIL

fLAMP

fLAMP

SCR1

VBATTERY

3 COIL

L2

470µH, 3Ω

7 CINT

SCR2

D1*

1N4148

** CINT

0.1µF

4

5

EL1

EL2

EL Lamp

NOTES: * Optional Component

** CINT may be decreased to change the square wave output to a sawtooth waveform.

Figure 1. Internal Diagram of the SP4405

SP4405DS/18

SP4405 Low Voltage Electroluminescent Lamp Driver

4

© Copyright 2000 Sipex Corporation

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