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Fairchild Semiconductor |
OPTICALLY ISOLATED
ERROR AMPLIFIER
FOD2741A
FOD2741B
FOD2741C
DESCRIPTION
The FOD2741 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 con-
verters.
When using the FOD2741, 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 dip white package.
FEATURES
• Optocoupler, precision reference and error amplifier in single package
• 2.5V reference
• CTR 100% to 200%
• 5,000V RMS isolation
• UL approved E90700, Volume 2
CSA approval 1296837
VDE approval 40002463
BSI approval 8702, 8703
• Low temperature coefficient 50 ppm/°C max
• FOD2741A: tolerance 0.5%
FOD2741B: tolerance 1%
FOD2741C: tolerance 2%
APPLICATIONS
• Power supplies regulation
• DC to DC converters
8
1
8
1
8
1
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 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 15
4/14/03
FOD2741A
TYPICAL APPLICATION
OPTICALLY ISOLATED
ERROR AMPLIFIER
FOD2741B
FOD2741C
FAN4803
V1 PWM
Control
FOD2741
28
6
37
5
VO
R1
R2
ABSOLUTE MAXIMUM RATINGS (TA = 25°C Unless otherwise specified.)
Parameter
Symbol
Value
Units
Storage Temperature
Operating Temperature
Lead Solder Temperature
Input Voltage
Input DC Current
Collector-Emitter Voltage
Emitter-Collector Voltage
Collector Current
Input Power Dissipation (note 1)
Transistor Power Dissipation (note 2)
Total Power Dissipation (note 3)
TSTG
TOPR
TSOL
VLED
ILED
VCEO
VECO
IC
PD1
PD2
PD3
-55 to +125
-25 to +85
260 for 10 sec.
37
20
30
7
50
145
85
145
°C
°C
°C
V
mA
V
V
mA
mW
mW
mW
Notes
1. Derate linearly from 25°C at a rate of 2.42 mW/ °C
2. Derate linearly from 25°C at a rate of 1.42 mW/ °C.
3. Derate linearly from 25°C at a rate of 2.42 mW/ °C.
4. Functional operation under these conditions is not implied. Permanent damage may occur if the device is subjected to conditions
outside these ratings.
© 2003 Fairchild Semiconductor Corporation
Page 2 of 15
4/14/03
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