OPTICALLY ISOLATED
ERROR AMPLIFIER
FOD2712
DESCRIPTION
The FOD2712 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%.
SEATING PLANE
PACKAGE DIMENSIONS
0.164 (4.16)
0.144 (3.66)
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 FOD2712, 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 compact 8-pin small outline package.
1
0.202 (5.13)
0.182 (4.63)
0.143 (3.63)
0.123 (3.13)
0.010 (0.25)
0.006 (0.16)
FEATURES
• Optocoupler, precision reference and
error amplifier in single package
• 1.240V ± 1% reference
• CTR 100% to 200%
• 2,500V RMS isolation
• VDE approval 136616
• BSI approval 8661 and 8662
• UL approval E90700
• CSA approval 1113643
FUNCTIONAL BLOCK DIAGRAM
0.021 (0.53)
0.011 (0.28)
0.008 (0.20)
0.003 (0.08)
0.050 (1.27)
TYP
0.244 (6.19)
0.224 (5.69)
Lead Coplanarity : 0.004 (0.10) MAX
NC
1
8 LED
C
2
7 FB
E
3
6 COMP
NC
APPLICATIONS
• Power system for workstations
• Telecom central office supply
• Telecom bricks
4
5 GND
NOTE
All dimensions are in inches (millimeters)
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
4/10/03
OPTICALLY ISOLATED
ERROR AMPLIFIER
FOD2712
TYPICAL APPLICATION
V
1
FAN4803
PWM
Control
V
O
FOD2712
2
8
6
R1
3
7
R2
5
ABSOLUTE MAXIMUM RATINGS
(T
A
= 25°C Unless otherwise specified.)
Parameter
Storage Temperature
Operating Temperature
Reflow Temperature Profile (refer to fig. 21)
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)
V
LED
I
LED
V
CEO
V
ECO
I
C
PD1
PD2
PD3
13.2
20
30
7
50
145
85
145
V
mA
V
V
mA
mW
mW
mW
Symbol
T
STG
T
OPR
Value
-55 to +125
-40 to +85
Units
°C
°C
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 13
4/10/03
OPTICALLY ISOLATED
ERROR AMPLIFIER
FOD2712
ELECTRICAL CHARACTERISTICS
(V
CC
= 12V, T
A
= 25°C Unless otherwise specified.)
INPUT CHARACTERISTICS
Parameter
LED forward voltage
Reference voltage
(-40 to +85°C)
(25°C)
Deviation of V
REF
over temperature - See Note 1
Ratio of Vref variation
to the output of the error amplifier
Feedback input current
(V
COMP
= V
FB
, I
LED
= 10 mA (Fig.1)
V
REF
1.221
1.228
1.240
4
-1.5
0.15
0.15
55
0.001
0.25
1.259
1.252
12
-2.7
0.5
0.3
80
0.1
V
mV
mV/V
µA
µA
µA
µA
Ohm
Test Conditions
(I
LED
= 10 mA, V
COMP
= V
FB
)(Fig.1)
Symbol
V
F
Min
Typ**
Max
1.5
Unit
V
(T
A
= -40 to +85°C) V
REF (DEV)
(I
LED
= 10 mA,
V
COMP
= V
REF
to 12 V) (Fig.2)
∆
V
REF
/
∆
V
COMP
I
REF
I
REF (DEV)
I
LED (MIN)
I
(OFF)
|Z
OUT
|
(I
LED
= 10 mA, R1 = 10 k
Ω
) (Fig.3)
(T
A
= -40 to +85°C)
(V
COMP
= V
FB
) (Fig.1)
(V
LED
= 6 V, V
FB
= 0) (Fig.4)
(V
COMP
= V
FB
, I
LED
= 0.1 mA to 15 mA,
f<1 kHZ)
Deviation of I
REF
over temperature - See Note 1
Minimum drive current
Off-state error amplifier current
Error amplifier
output impedance - See Note 2
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
REF
,
is defined as:
∆V
REF
{
V
REF
(
DEV
)
/V
REF
(
T
A
= 25°C
) } ×
10
(
ppm/°C
)
= ----------------------------------------------------------------------------------------------------
-
∆T
A
6
where
∆
T
A
is the rated operating free-air temperature range of the device.
2. The dynamic impedance is defined as |Z
OUT
| =
∆
V
COMP
/
∆
I
LED
. When the device is operating with two external resistors (see
Figure 2), the total dynamic impedance of the circuit is given by:
∆V
R1
Z
OUT, TOT
= -------
≈
Z
OUT
×
1 + -------
-
-
∆I
R2
© 2003 Fairchild Semiconductor Corporation
Page 3 of 13
4/10/03
OPTICALLY ISOLATED
ERROR AMPLIFIER
FOD2712
OUTPUT CHARACTERISTICS
(T
A
= 25°C Unless otherwise specified.)
Parameter
Collector dark current
Collector-emitter voltage breakdown
Emitter-collector voltage breakdown
Test Conditions
(V
CE
= 10 V) (Fig. 5)
(I
C
= 1.0mA)
(I
E
= 100 µA)
Symbol
I
CEO
BV
CEO
BV
ECO
70
7
Min
Typ
Max
50
Unit
nA
V
V
TRANSFER CHARACTERISTICS
(T
A
= 25°C Unless otherwise specified.)
Parameter
Current transfer ratio
Collector-emitter
saturation voltage
Test Conditions
(I
LED
= 10 mA, V
COMP
= V
FB
,
V
CE
= 5 V) (Fig. 6)
Symbol
CTR
Min
100
Typ
Max
200
0.4
Unit
%
V
(I
LED
= 10 mA, V
COMP
= V
FB
,
V
CE (SAT)
I
C
= 2.5 mA) (Fig. 6)
ISOLATION CHARACTERISTICS
(T
A
= 25°C Unless otherwise specified.)
Parameter
Input-output insulation
leakage current
Withstand insulation
voltage
Resistance (input to output)
Test Conditions
(RH = 45%, T
A
= 25°C, t = 5s,
V
I-O
= 3000 VDC) (note. 1)
(RH <= 50%, T
A
= 25°C, t = 1 min)
(notes. 1)
V
I-O
= 500 VDC (note. 1)
Symbol
I
I-O
V
ISO
R
I-O
2500
10
12
Min
Typ
Max
1.0
Unit
µA
Vrms
Ohm
SWITCHING CHARACTERISTICS
(T
A
= 25°C Unless otherwise specified.)
Parameter
Bandwidth
Common mode transient
immunity at output high
Common mode transient
immunity at output low
Test Conditions
(Fig. 7)
(I
LED
= 0 mA,
V
cm
= 10 V
PP
RL = 2.2 kΩ (Fig. 8) (note. 2)
(I
LED
= 10 mA,
V
cm
= 10 V
PP
RL = 2.2 kΩ (Fig. 8) (note. 2)
Symbol
B
W
CMH
CML
Min
Typ
10
1.0
1.0
Max
Unit
kHZ
kV/µs
kV/µs
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 13
4/10/03
OPTICALLY ISOLATED
ERROR AMPLIFIER
FOD2712
I
(LED)
I
(LED)
8
V
F
6
V
7
V
REF
5
3
V
R1
6
7
V
COMP
R2
V
REF
5
3
2
8
2
FIG. 1. V
REF
, V
F,
I
LED
(min) TEST CIRCUIT
FIG. 2.
∆V
REF/
∆V
COMP
TEST CIRCUIT
I
(LED)
8
2
I
(OFF)
8
2
I
REF
6
V
R1
5
5
7
3
V
6
V
(LED)
7
3
FIG. 3. I
REF
TEST CIRCUIT
FIG. 4. I
(OFF)
TEST CIRCUIT
8
I
CEO
2
V
CE
I
(LED)
8
2
V
CE
6
V
7
V
COMP
V
REF
3
I
(C)
6
7
3
5
5
FIG. 5. I
CEO
TEST CIRCUIT
FIG. 6. CTR, V
CE(sat)
TEST CIRCUIT
© 2003 Fairchild Semiconductor Corporation
Page 5 of 13
4/10/03
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