OPTICALLY ISOLATED ERROR AMPLIFIER
Description
OPTICALLY ISOLATED ERROR AMPLIFIER FOD2742A
DESCRIPTION
The FOD2742 Optically Isolated Amplifier consists of the popular KA431 precision programmable shunt reference and an optocoupler.
The optocoupler is a gallium arsenide (GaAs) light emitting diode optically coupled to a silicon phototransistor.
It comes in 3 grades of reference voltage tolerance = 2%, 1%, and 0.
5%.
The Current Transfer Ratio (CTR) ranges from 100% to 200%.
It also has an outstanding temperature coefficient of 50 ppm/°C.
It is primarily intended for use as the error amplifier/ reference voltage/optocoupler function in isolated ac to dc power supplies and dc/dc converters.
FUNCTIONAL BLOCK DIAGRAM
FOD2742B
FOD2742C
When using the FOD2742, power supply designers can reduce the component count and save space in tightly packaged designs.
The tight tolerance reference eliminates the need for adjustments in many applications.
The device comes in a 8-pin small outline package.
FEATURES
• Optocoupler, precision reference and error amplifier in single package • 2.
5V reference • CTR 100% to 200% • 2,500V RMS isolation • UL approval E90700, Volume 2 • VDE approval 136616 • FOD2742A: tolerance 0.
5% FOD2742B: tolerance 1% FOD2742C: tolerance 2% • BSI approval 8661, 8662 • CSA approval 1113643
NC
1
8 LED
C
2
7 FB
E
3
6 COMP
NC
4
5 GND
• Low temperature coefficient 50 ppm/°C max
APPLICATIONS
• Power supplies regulation • DC to DC converters
PIN DEFINITIONS
Pin Number 1 2 3 4 5 6 7 8 Pin Name NC C E NC GND COMP FB LED Pin function description Not connected Phototransistor Collector Phototransistor Emitter Not connected Ground Error Amplifier Compensation.
This pin is the output of the error amplifier.
* Voltage Feedback.
This pin is the inverting input to the error amplifier Anode LED.
This pin is the input to the light emitting diode.
* The compensation network must be attached between pins 6 and 7.
© 2003 Fairchild Semiconductor Corporation
Page 1 of 13
8/27/03
OPTICALLY ISOLATED ERROR AMPLIFIE...
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