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| FOD2742A_04 Datasheet, PDF (1/13 Pages) Fairchild Semiconductor – OPTICALLY ISOLATED ERROR AMPLIFIER | |||
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OPTICALLY ISOLATED
ERROR AMPLIFIER
FOD2742A
FOD2742B
FOD2742C
DESCRIPTION
The FOD2742 Optically Isolated Ampliï¬er 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 coefï¬cient of 50 ppm/°C. It is primarily intended for use as the error ampliï¬er/
reference voltage/optocoupler function in isolated ac to dc power supplies and dc/dc con-
verters.
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 ampliï¬er in single package
⢠2.5V reference
⢠CTR 100% to 200%
⢠2,500V RMS isolation
⢠UL approval E90700, Volume 2 ⢠BSI approval 8661, 8662
⢠VDE approval 136616
⢠CSA approval 1113643
⢠Low temperature coefï¬cient 50 ppm/°C max
⢠FOD2742A: tolerance 0.5%
FOD2742B: tolerance 1%
FOD2742C: tolerance 2%
APPLICATIONS
⢠Power supplies regulation
⢠DC to DC converters
FUNCTIONAL BLOCK DIAGRAM
NC 1
C2
E3
NC 4
8 LED
7 FB
6 COMP
5 GND
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 Ampliï¬er Compensation. This pin is the output of the error ampliï¬er. *
Voltage Feedback. This pin is the inverting input to the error ampliï¬er
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
12/9/04
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