CPC6826 datasheet(9/12 Pages) CLARE

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CPC6826

R00C

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4. Functional Description

4.1 Overview

The CPC6826 is an EL lamp driver designed for

battery applications operating from an input supply

voltage range of 1.8V to 3.5V and generating an AC

output voltage of 180Vp-p. The device is capable of

driving lamp panels ranging from 1 in2 to 5 in2.

The CPC6826 IC main block architecture is made up

of two independent oscillators, which control the

switching of a power MOSFET and an H-bridge.

Adjustment of two external resistors, RSW and REL,

sets the frequencies of the oscillators, thus allowing

the designer to maximize efficiency and to increase

the brightness of the lamp.

To conserve supply power and extend battery life, the

CPC6826 automatically shuts down the switcher

circuit whenever switcher output power exceeds load

requirements. Supply power can also be conserved

manually by disabling the switching circuit: pull pin 2,

RSW, to ground.

4.2 Regulation

The circuit configuration is based on simple boost

converter topology. This method provides excellent

efficiency, minimizes loss of energy, and allows

smaller components to be used in the design. Only a

few passive components (an inductor, a capacitor, two

resistors, and a diode) are required to complete the

simple boost switcher circuit.

When power is applied to VDD, the internal feedback

voltage VSEN is less than VREF causing the

comparator output to go low, which enables the

switching power MOSFET oscillator. When turned on,

the internal low impedance switching MOSFET

causes current to flow through the external inductor.

With current flowing in the inductor, the switching

MOSFET is turned off causing a flyback voltage to

develop across the inductor. As the inductor's flyback

voltage increases to a level greater than a diode drop

above the voltage across the capacitor on the CS pin,

charge stored in the inductor is transferred into the

COUT capacitor. This operating cycle continues until

the VSEN voltage is above the VREF in which case the

comparator disables the Switch Oscillator.

The internal high voltage H-Bridge section is enabled

by external resistor REL at pin 3 and VDD on pin 1. The

H-bridge operation is controlled by output oscillator

waveforms driving H-bridge high-side and low-side

MOSFETs. Selecting the value of REL allows the

designer to set the frequency of the internal oscillator

to meet design requirements. By alternately switching

the terminals of the lamp between high voltage supply

and ground the 180VP-P potential develops across the

EL lamp.

Switch

Osc

Output

Osc

Vref

Vsen

Disable

1 (V

DD)

2 (R

SW-osc)

3 (R

EL-osc)

4 (GND)

8 (V

7 (V

6 (C

5 (L

OUT

CPC6826

EL Lamp

IN +

IN -

CPC6826 Datasheet(PDF) 9 Page - Clare, Inc.

CPC6826 Datasheet(HTML) 9 Page - Clare, Inc.

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