Page 1
DESCRIPTION
The FOD2711 Optically Isolated Amplifier consists of the popular RC431A precision
programmable shunt reference and an optocoupler. The optocoupler is a gallium arsenide
(GaAs) light emitting diode optically coupled to a silicon phototransistor. The reference
voltage tolerance is 1%. The current transfer ratio (CTR) ranges from 100% to 200%.
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.
When using the FOD2711, 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.
OPTICALLY ISOLATED
ERROR AMPLIFIER
FOD2711
8
1
8
1
8
1
FEATURES
• Optocoupler, precision reference and error amplifier in single package
• 1.240V ± 1% reference
• CTR 100% to 200%
• 5,000V RMS isolation
• UL approval E90700, Volume 2
CSA approval 1296837
VDE approval 40002463
BSI approval 8702, 8703
APPLICATIONS
•Power supplies regulation
• DC to DC converters
PIN DEFINITIONS
Pin Number Pin Name Pin function description
1NCNot connected
2CPhototransistor Collector
3EPhototransistor Emitter
4NCNot connected
5 GND Ground
6 COMP Error Amplifier Compensation. This pin is the output of the error amplifier. *
7FBVoltage Feedback. This pin is the inverting input to the error amplifier
8 LED Anode LED. This pin is the input to the light emitting diode.
FUNCTIONAL BLOCK DIAGRAM
NC
1
C
2
E
3
NC
4 5
8
7
6
LED
FB
COMP
GND
* The compensation network must be attached between pins 6 and 7.
© 2003 Fairchild Semiconductor Corporation
Page 1 of 15
4/14/03
Page 2
TYPICAL APPLICATION
FAN4803
V
1
PWM
Control
FOD2711
OPTICALLY ISOLATED
ERROR AMPLIFIER
FOD2711
V
O
2
3
ABSOLUTE MAXIMUM RATINGS
Parameter Symbol Value Units
Storage Temperature T
Operating Temperature T
Lead Solder Temperature T
Input Voltage V
Input DC Current I
Collector-Emitter Voltage V
Emitter-Collector Voltage V
Collector Current I
Input Power Dissipation (note 1) PD1 145 mW
Tr ansistor Power Dissipation (note 2) PD2 85 mW
Total Power Dissipation (note 3) PD3 145 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.
(T
= 25°C Unless otherwise specified.)
A
STG
OPR
SOL
LED
LED
CEO
ECO
8
6
7
5
-55 to +125 °C
-40 to +85 °C
260 for 10 sec. °C
13.2 V
20 mA
30 V
7V
C
50 mA
R1
R2
© 2003 Fairchild Semiconductor Corporation
Page 2 of 15
4/14/03
Page 3
/ ∆
∆
/ ∆
OPTICALLY ISOLATED
ERROR AMPLIFIER
FOD2711
ELECTRICAL CHARACTERISTICS
INPUT CHARACTERISTICS
Parameter Test Conditions Symbol Min Typ** Max Unit
LED forward voltage (I
Reference voltage
(-40 to +85°C) (V
(25°C) 1.228 1.240 1.252
Deviation of V
Ratio of Vref variation
to the output of the error amplifier
Feedback input current (I
Deviation of I
Minimum drive current (V
Off-state error amplifier current (V
Error amplifier
output impedance - See Note 2
over temperature - See Note 1
REF
over temperature - See Note 1
REF
(V
(T
= 25°C Unless otherwise specified.)
A
= 10 mA, V
LED
= V
COMP
LED
, I
FB
, I
FB
= V
= 6 V, V
LED
COMP
V
= 10 mA, R1 = 10 k Ω ) (Fig.3) I
LED
= V
COMP
= V
COMP
= 10 mA (Fig.1)
LED
(T
= -40 to +85°C) V
A
(I
LED
to 12 V) (Fig.2)
REF
= -40 to +85°C) I
(T
A
= V
COMP
= 0) (Fig.4) I
FB
= 0.1 mA to 15 mA,
)(Fig.1) V
FB
= 10 mA,
) (Fig.1) I
FB
f<1 kHZ)
F
V
REF
REF (DEV)
V
REF
V
COMP
REF
REF (DEV)
LED (MIN)
(OFF)
|Z
OUT
1.221 1.259
4 12 mV
-1.5 -2.7 mV/V
0.15 0.5 µA
0.15 0.3 µA
55 80 µA
0.001 0.1 µA
| 0.25 Ohm
1.5 V
V
1. The deviation parameters V
REF(DEV)
and I
REF(DEV)
are defined as the differences between the maximum and minimum values
obtained over the rated temperature range. The average full-range temperature coefficient of the reference input voltage, ∆ V
is defined as:
A
OUT
25°C=(){}106×
| = ∆ V
COMP
I
. When the device is operating with two external resistors (see
LED
V
∆V
REF
where ∆ T
ppm/°C()
is the rated operating free-air temperature range of the device.
A
REF DEV()/VREFTA
-----------------------------------------------------------------------------------------------------=
∆T
2. The dynamic impedance is defined as |Z
Figure 2), the total dynamic impedance of the circuit is given by:
Z
OUT, TOT
∆V
=
--------Z
∆I
OUT
R1
1
--------+×≈
R2
REF
,
© 2003 Fairchild Semiconductor Corporation
Page 3 of 15
4/14/03
Page 4
OPTICALLY ISOLATED
ERROR AMPLIFIER
FOD2711
OUTPUT CHARACTERISTICS
(T
= 25°C Unless otherwise specified.)
A
Parameter Test Conditions Symbol Min Typ Max Unit
Collector dark current (V
Emitter-collector voltage breakdown (I
Collector-emitter voltage breakdown (I
TRANSFER CHARACTERISTICS
(T
= 10 V) (Fig. 5) I
CE
= 100 µA) BV
E
= 1.0mA) BV
C
= 25°C Unless otherwise specified.)
A
CEO
ECO
CEO
50 nA
7V
70 V
Parameter Test Conditions Symbol Min Typ Max Unit
(I
(I
LED
LED
Current transfer ratio
Collector-emitter
saturation voltage
ISOLATION CHARACTERISTICS
= 10 mA, V
V
CE
= 10 mA, V
I
= 2.5 mA) (Fig. 6)
C
(T
= 25°C Unless otherwise specified.)
A
= V
COMP
FB
= 5 V) (Fig. 6)
= V
COMP
FB
,
CTR 100 200 %
,
V
CE
(SAT)
0.4 V
Parameter Test Conditions Symbol Min Typ Max Unit
Input-output insulation
leakage current
Withstand insulation
voltage
Resistance (input to output) V
(RH = 45%, T
V
= 3000 VDC) (note. 1)
I-O
(RH <= 50%, T
I-O
= 25°C, t = 5s,
A
= 25°C, t = 1 min)
A
(note 1)
= 500 VDC (note. 1) R
I
I-O
V
5000 Vrms
ISO
12
I-O
10
1.0 µA
Ohm
SWITCHING CHARACTERISTICS (T
= 25°C Unless otherwise specified.)
A
Parameter Test Conditions Symbol Min Typ Max Unit
Bandwidth (Fig. 7) B
Common mode transient
immunity at output high
Common mode transient
immunity at output low
= 0 mA, Vcm = 10 V
(I
LED
RL = 2.2 kΩ (Fig. 8) (note 2)
= 10 mA, Vcm = 10 V
(I
LED
RL = 2.2 kΩ (Fig. 8) (note 2)
PP
CMH 1.0 kV/µs
PP
CML 1.0 kV/µs
W
10 kHZ
Notes
1. Device is considered as a two terminal device: Pins 1, 2, 3 and 4 are shorted together and Pins 5, 6, 7 and 8 are shorted together.
2. Common mode transient immunity at output high is the maximum tolerable (positive) dVcm/dt on the leading edge of the
common mode impulse signal, Vcm, to assure that the output will remain high. Common mode transient immunity at output low
is the maximum tolerable (negative) dVcm/dt on the trailing edge of the common pulse signal,Vcm, to assure that the output will
remain low.
© 2003 Fairchild Semiconductor Corporation
Page 4 of 15
4/14/03
Page 5
OPTICALLY ISOLATED
ERROR AMPLIFIER
FOD2711
I
I
(LED)
V
82
V
F
6
7
V
REF
5
3
V
R2
(LED)
8
6R1
7
V
COMP
V
REF
5
2
3
FIG. 1. V
V
, VF, I
REF
FIG. 3. I
8
6
7
5
(min) TEST CIRCUIT
LED
I
(LED)
8
I
REF
6
7
R1
5
TEST CIRCUIT
REF
2
V
3
FIG. 2. ∆V
2
3
V
REF/∆VCOMP
I
(OFF)
V
(LED)
FIG. 4. I
I
I
CEO
CE
(LED)
V
TEST CIRCUIT
(OFF)
8
6
7
V
REF
5
8
6
7
5
TEST CIRCUIT
V
COMP
2
3
I
C
2
V
CE
3
FIG. 5. I
TEST CIRCUIT FIG. 6. CTR, V
CEO
© 2003 Fairchild Semiconductor Corporation
Page 5 of 15
TEST CIRCUIT
CE(sat)
4/14/03
Page 6
VCC = +5V DC
OPTICALLY ISOLATED
ERROR AMPLIFIER
FOD2711
= 10 mA
I
F
R
L
V
OUT
1
2
3
4
8
7
0.1 V
PP
6
5
1µf
47Ω
V
IN
0.47V
Fig. 7 Frequency Response Test Circuit
= +5V DC
V
CC
I
= 0 mA (A)
F
IF = 10 mA (B)
R1
2.2kΩ
1
8
V
OUT
© 2003 Fairchild Semiconductor Corporation
2
3
4
VCM
_
10V
+
P-P
7
6
5
Fig. 8 CMH and CML Test Circuit
Page 6 of 15
A
B
4/14/03
Page 7
TYPICAL PERFORMANCE CURVES
OPTICALLY ISOLATED
ERROR AMPLIFIER
FOD2711
Fig. 9a LED Current vs Cathode Voltage
15
TA = 25°C
= V
V
COMP
10
FB
5
0
-5
- SUPPLY CURRENT (mA)
LED
-10
I
-15
-1.0 -0.5 0.0 0.5 1.0 1.5
V
- CATHODE VOLTAGE (V)
COMP
Fig. 10 Reference Voltage vs Ambient Temperature
1.244
I
=
10mA
LED
1.242
1.240
1.238
1.236
- REFERENCE VOLTAGE (V)
1.234
REF
V
1.232
1.230
-40 -20 0 20 40 60 80 100
TA - AMBIENT TEMPERATURE (°C)
Fig. 9b LED Current vs Cathode Voltage
150
TA = 25°C
V
= V
COMP
FB
100
50
0
-50
- SUPPLY CURRENT (mA)
LED
I
-100
-150
-1 0 1 2
V
- CATHODE VOLTAGE (V)
COMP
Fig. 11 Reference Current vs Ambient Temperature
280
I
= 10mA
LED
R
= 10 kΩ
1
260
240
220
200
180
160
- REFERENCE CURRENT (nA)
REF
I
140
120
-40 -20 0 20 40 60 80 100
TA - AMBIENT TEMPERATURE (°C)
© 2003 Fairchild Semiconductor Corporation
Fig. 12 Off-State Current vs Ambient Temperature
V
= 13.2V
C
C
1000
100
10
1
- OFF-STATE CURRENT (NA)
OFF
I
0.1
-40 -20 0 20 40 60 80 100
TA - AMBIENT TEMPERATURE (°C)
Page 7 of 15
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Page 8
OPTICALLY ISOLATED
ERROR AMPLIFIER
FOD2711
Fig. 13 Forward Current vs Forward Voltage
20
15
70°C
10
- FORWARD CURRENT (mA)
5
F
I
0.9 1.0 1.1 1.2 1.3 1.4
VF - FORWARD VOLTAGE (V)
25°C
C
0°
Fig. 15 Collector Current vs Ambient Temperature
30
V
= 5V
E
C
25
I
= 20mA
I
LED
LED
I
I
LED
= 10mA
LED
= 5mA
= 1mA
20
15
10
5
IC - COLLECTOR CURRENT (mA)
0
0102030405060708090100
TA - AMBIENT TEMPERATURE (°C)
Fig. 14 Dark Current vs Ambient Temperature
10000
- DARK CURRENT (nA)
CEO
I
= 10V
V
E
C
1000
100
10
1
0.1
-40 -20 0 20 40 60 80 100
TA - AMBIENT TEMPERATURE (°C)
Fig. 16 Current Transfer Ratio vs LED Current
= 5V
V
E
C
140
120
0°
100
80
60
(IC/IF) - CURRENT TRANSFER RATIO (%)
40
10501520253035404550
I
- FORWARD CURRENT (mA)
LED
C
25°C
70°C
© 2003 Fairchild Semiconductor Corporation
Fig. 17 Saturation Voltage vs Ambient Temperature
0.26
0.24
0.22
0.20
0.18
0.16
- SATURATION VOLTAGE (V)
0.14
CE(SAT)
0.12
V
0.10
-40 -20 0 20 40 60 80 100
TA - AMBIENT TEMPERATURE (°C)
Page 8 of 15
4/14/03
Page 9
OPTICALLY ISOLATED
ERROR AMPLIFIER
FOD2711
Fig. 18 Collector Current vs Collector Voltage
35
30
25
20
15
10
- COLLECTOR CURRENT (mA)
C
I
0
T
C
= 25
A
I
= 20mA
LED
I
= 10mA
LED
I
= 5mA
I
LED
LED
= 1mA
5
0
012345678910
VCE - COLLECTOR-EMITTER VOLTAGE (V)
Fig. 20 Voltage Gain vs Frequency
VCC = 10 V
IF = 10 mA
0
Fig. 19 Rate of Change Vref to Vcomp vs Temperature
-0.2
-0.4
-0.6
-0.8
-1.0
-1.2
-1.4
DELTA VREF / DELTA VCOMP ( mV/V)
-1.6
-40-60 -20 0 20 40 60 80 100 120
TEMPERATURE - °C
RL=100Ω
-5
VOLTAGE GAIN - DB
-10
-15
RL=1kΩ
RL=500Ω
1010.1 100 1000
FREQUENCY - KHZ
© 2003 Fairchild Semiconductor Corporation
Page 9 of 15
4/14/03
Page 10
OPTICALLY ISOLATED
ERROR AMPLIFIER
FOD2711
The FOD2711
The FOD2711 is an optically isolated error amplifier. It incorporates three of the most common elements necessary to make
an isolated power supply, a reference voltage, an error amplifier, and an optocoupler. It is functionally equivalent to the
popular RC431A shunt voltage regulator plus the CNY17F-3
optocoupler.
Powering the Secondary Side
The LED pin in the FOD2711 powers the secondary side, and
in particular provides the current to run the LED. The actual
structure of the FOD2711 dictates the minimum voltage that
can be applied to the LED pin: The error amplifier output has a
minimum of the reference voltage, and the LED is in series
with that. Minimum voltage applied to the LED pin is thus
1.24V + 1.5V = 2.74V. This voltage can be generated either
directly from the output of the converter, or else from a slaved
secondary winding. The secondary winding will not affect regulation, as the input to the FB pin may still be taken from the
output winding.
The LED pin needs to be fed through a current limiting resistor.
The value of the resistor sets the amount of current through
the LED, and thus must be carefully selected in conjunction
with the selection of the primary side resistor.
Feedback
Output voltage of a converter is determined by selecting a
resistor divider from the regulated output to the FB pin. The
FOD2711 attempts to regulate its FB pin to the reference
voltage, 1.24V. The ratio of the two resistors should thus be:
R
TOP
-------------------------R
BOTTOM
The absolute value of the top resistor is set by the input offset
current of 0.8µA. To achieve 1% accuracy, the resistance of
R
should be:
TOP
V
OUT
-------------------------------- 8 0 µA>
R
TOP
V
OUT
-------------- 1–=
V
REF
1.24–
Compensation
The compensation pin of the FOD2711 provides the opportunity for the designer to design the frequency response of the
converter. A compensation network may be placed between
the COMP pin and the FB pin. In typical low-bandwidth
systems, a 0.1µF capacitor may be used. For converters with
more stringent requirements, a network should be designed
based on measurements of the system’s loop. An excellent
reference for this process may be found in “Practical Design of
Power Supplies” by Ron Lenk, IEEE Press, 1998.
Secondary Ground
The GND pin should be connected to the secondary ground of
the converter.
No Connect Pins
The NC pins have no internal connection. They should not
have any connection to the secondary side, as this may
compromise the isolation structure.
Photo-Transistor
The Photo-transistor is the output of the FOD2711. In a normal
configuration the collector will be attached to a pull-up resistor
and the emitter grounded. There is no base connection necessary.
The value of the pull-up resistor, and the current limiting resistor feeding the LED, must be carefully selected to account for
voltage range accepted by the PWM IC, and for the variation in
current transfer ratio (CTR) of the opto-isolator itself.
Example: The voltage feeding the LED pins is +12V, the voltage feeding the collector pull-up is +10V, and the PWM IC is
the Fairchild KA1H0680, which has a 5V reference. If we
select a 10KΩ resistor for the LED, the maximum current the
LED can see is (12V-2.74V) /10KΩ = 926µA. The CTR of the
opto-isolator is a minimum of 100%, and so the minimum
collector current of the photo-transistor when the diode is full
on is also 926µA. The collector resistor must thus be such that:
10V 5V–
------------------------------------926µA or R
R
COLLECTOR
COLLECTOR
5.4KΩ;><
© 2003 Fairchild Semiconductor Corporation
select 10KΩ to allow some margin.
Page 10 of 15
4/14/03
Page 11
OPTICALLY ISOLATED
0.070 (1.78)
0.060 (1.52)
0.030 (0.76)
0.100 (2.54)
0.295 (7.49)
0.415 (10.54)
ERROR AMPLIFIER
FOD2711
Package Dimensions (Through Hole)
PIN 1
ID.
0.270 (6.86)
0.250 (6.35)
8
0.070 (1.78)
0.045 (1.14)
0.154 (3.90)
0.120 (3.05)
0.020 (0.51) MIN
0.016 (0.40)
0.008 (0.20)
15° MAX
0.300 (7.62)
TYP
0.200 (5.08)
0.140 (3.55)
SEATING PLANE
0.022 (0.56)
0.016 (0.41)
3
241
56 7
0.390 (9.91)
0.370 (9.40)
0.100 (2.54) TYP
Package Dimensions (Surface Mount)
0.390 (9.91)
0.370 (9.40)
3214
PIN 1
ID.
Package Dimensions (0.4"Lead Spacing)
PIN 1
0.270 (6.86)
0.250 (6.35)
8
0.070 (1.78)
0.045 (1.14)
0.154 (3.90)
0.120 (3.05)
ID.
0.004 (0.10) MIN
0.016 (0.40)
0.008 (0.20)
0° to 15°
0.400 (10.16)
TYP
0.200 (5.08)
0.140 (3.55)
SEATING PLANE
0.022 (0.56)
0.016 (0.41)
3
241
56 7
0.390 (9.91)
0.370 (9.40)
0.100 (2.54) TYP
8 - Pin Dip
0.270 (6.86)
0.250 (6.35)
0.100 (2.54)
TYP
8
0.070 (1.78)
0.045 (1.14)
0.022 (0.56)
0.016 (0.41)
0.020 (0.51)
MIN
567
Lead Coplanarity : 0.004 (0.10) MAX
© 2003 Fairchild Semiconductor Corporation
0.300 (7.62)
TYP
0.045 [1.14]
0.315 (8.00)
MIN
0.405 (10.30)
MIN
0.016 (0.41)
0.008 (0.20)
NOTE
All dimensions are in inches (millimeters)
Page 11 of 15
4/14/03
Page 12
ORDERING INFORMATION
Example: FOD2711 X Y
OPTICALLY ISOLATED
ERROR AMPLIFIER
FOD2711
X
Packaging Option
T: 0.4” Lead Spacing
S: Surface Mount Lead Bend
SD: Surface Mount Tape and Reel (1000 per reel)
MARKING INFORMATION
Definitions
Y
V: VDE tested
XXV
43
2711
BYY
5
1
2
6
1Fairchild logo
2Device number
VDE mark (Note: Only appears on parts ordered with VDE
3
option – See order entry table)
4Two digit year code, e.g., ‘03’
5Two digit work week ranging from ‘01’ to ‘53’
6 Assembly package code
© 2003 Fairchild Semiconductor Corporation
Page 12 of 15
4/14/03
Page 13
Carrier Tape Specifications
OPTICALLY ISOLATED
ERROR AMPLIFIER
FOD2711
D
P
K
t
0
0
P
2
0
E
F
W
D
1
W
1
d
User Direction of Feed
A
0
B
0
P
Description Symbol Dimension in mm
Tape Width W 16.0 ± 0.3
Tape Thickness t 0.30 ± 0.05
Sprocket Hole Pitch P
Sprocket Hole Diameter D
0
0
4.0 ± 0.1
1.55 ± 0.05
Sprocket Hole Location E 1.75 ± 0.10
Pocket Location
F 7.5 ± 0.1
P
2
4.0 ± 0.1
Pocket Pitch P 12.0 ± 0.1
Pocket Dimensions
Cover Tape Width W
A
0
B
0
K
0
1
10.30 ±0.20
10.30 ±0.20
4.90 ±0.20
1.6 ± 0.1
Cover Tape Thickness d 0.1 max
Max. Component Rotation or Tilt 10°
Min. Bending Radius R 30
© 2003 Fairchild Semiconductor Corporation
Page 13 of 15
4/14/03
Page 14
Reflow Profile
OPTICALLY ISOLATED
ERROR AMPLIFIER
FOD2711
300
C peak
250
200
150
100
50
Temperature (°C)
0
0.5 1 1.5 2 2.5 3 3.5 4 4.5
0
• Peak reflow temperature: 260 C (package surface temperature)
• Time of temperature higher than 183 C for 160 seconds or less
• One time soldering reflow is recommended
260
Time above 183 C, <160 sec
Ramp up = 2–10
Time (Minute)
245 C, 10–30 s
C/sec
© 2003 Fairchild Semiconductor Corporation
Page 14 of 15
4/14/03
Page 15
OPTICALLY ISOLATED
ERROR AMPLIFIER
FOD2711
DISCLAIMER
FAIRCHILD SEMICONDUCTOR RESERVES THE RIGHT TO MAKE CHANGES WITHOUT FURTHER NOTICE TO
ANY PRODUCTS HEREIN TO IMPROVE RELIABILITY, FUNCTION OR DESIGN. FAIRCHILD DOES NOT ASSUME
ANY LIABILITY ARISING OUT OF THE APPLICATION OR USE OF ANY PRODUCT OR CIRCUIT DESCRIBED HEREIN;
NEITHER DOES IT CONVEY ANY LICENSE UNDER ITS PATENT RIGHTS, NOR THE RIGHTS OF OTHERS.
LIFE SUPPORT POLICY
FAIRCHILD’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES
OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT OF FAIRCHILD SEMICONDUCTOR
CORPORATION. As used herein:
1. Life support devices or systems are devices or systems
which, (a) are intended for surgical implant into the body, or
(b) support or sustain life, and (c) whose failure to perform
when properly used in accordance with instructions for use
provided in the labeling, can be reasonably expected to
result in a significant injury of the user.
2. A critical component in any component of a life support
device or system whose failure to perform can be
reasonably expected to cause the failure of the life support
device or system, or to affect its safety or effectiveness.
© 2003 Fairchild Semiconductor Corporation
Page 15 of 15
4/14/03
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