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OPTICALLY ISOLATED ERROR AMPLIFIER FOD2743A
DESCRIPTION
The FOD2743 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 50% to 100%. 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. When using the FOD2743, 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.
8 1 8 1 8 1
FOD2743B
FOD2743C
FEATURES
Optocoupler, precision reference and error amplifier in single package 2.5V reference CTR 50% to 100% at 1mA 5,000V RMS isolation UL approval E90700, Vol. 2 CSA approval 1296837 VDE approval pending BSI approval pending * Low temperature coefficient 50 ppm/C max * FOD2743A: tolerance 0.5% FOD2743B: tolerance 1% FOD2743C: tolerance 2% * * * * *
FUNCTIONAL BLOCK DIAGRAM
LED
1
8 NC
COMP
2
7C
GND
3
6E
FB
4
5 NC
APPLICATIONS
* Power supplies regulation * DC to DC converters
PIN DEFINITIONS
Pin Number 1 2 3 4 5 6 7 8 Pin Name LED COMP GND FB NC E C NC Pin function description Anode LED. This pin is the input to the light emitting diode. Error Amplifier Compensation. This pin is the output of the error amplifier. * Ground Voltage Feedback. This pin is the inverting input to the error amplifier Not connected Phototransistor Emitter Phototransistor Collector Not connected
* The compensation network must be attached between pins 2 and 4.
(c) 2004 Fairchild Semiconductor Corporation
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OPTICALLY ISOLATED ERROR AMPLIFIER FOD2743A
TYPICAL APPLICATION
FOD2743B
FOD2743C
V1
FAN4803 PWM Control
VO
FOD2743 7 1
2
R1
6
4 R2
3
ABSOLUTE MAXIMUM RATINGS (TA = 25C Unless otherwise specified.)
Parameter Storage Temperature Operating Temperature Lead Solder Temperature Input Voltage Input DC Current Collector-Emitter Voltage Emitter-Collector Voltage Collector Current Input Power Dissipation Transistor Power Dissipation Total Power Dissipation (note 1) Symbol TSTG TOPR TSOL VLED ILED VCEO VECO IC PD1 PD2 PD3 Value -40 to +125 -25 to +85 260 for 10 sec. 37 20 70 7 50 145 85 145 Units C C C V mA V V mA mW mW mW
Notes 1. See derating graph fig 21. 2. Functional operation under these conditions is not implied. Permanent damage may occur if the device is subjected to conditions outside these ratings.
(c) 2004 Fairchild Semiconductor Corporation
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OPTICALLY ISOLATED ERROR AMPLIFIER FOD2743A FOD2743B FOD2743C
ELECTRICAL CHARACTERISTICS (TA = 25C Unless otherwise specified.) INPUT CHARACTERISTICS
Parameter LED Forward Voltage Test Conditions (ILED = 1 mA, VCOMP = VFB) (fig.1) ILED = 1 mA, VCOMP = VFB Symbol VF VREF Device ALL A Reference Voltage Deviation of VREF over temperature Ratio of VREF variation to the output of the error amplifier Feedback Input Current Deviation of IREF over temperature Minimum Drive Current Off-state error amplifier current Error amplifier output impedance (see note 2) ILED = 1 mA B C TA = -25C to +85C VREF (DEV) VCOMP = 10V to VREF VCOMP = 36V to 10V VREF/ VCOMP IREF IREF (DEV) ILED (MIN) I(OFF) |ZOUT| ALL ALL ALL ALL ALL ALL ALL 2.482 2.470 2.450 Min. Typ. 1.07 2.495 2.495 2.500 4.5 -0.4 -0.3 2 1 0.45 0.001 0.15 Max. 1.2 2.508 2.520 2.550 17 -2.7 -2.0 4 1.2 1.0 1.0 0.5 Unit V V V V mV mV/ V A A mA A
ILED = 1mA, R1 = 10k (fig 3) TA = -25C to +85C VCOMP = VFB (fig.1) VLED = 37V, VFB = 0 (fig 4.) VCOMP = VREF, ILED = 1mA to 20mA, f 1.0 kHz
1. The deviation parameters VREF(DEV) and IREF(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, VREF, is defined as: { V REF ( DEV ) /V REF ( T A = 25C ) } x 10 V REF ( ppm/C ) = ---------------------------------------------------------------------------------------------------T A
6
where TA is the rated operating free-air temperature range of the device. 2. The dynamic impedance is defined as |ZOUT| = VCOMP/ILED. 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 x 1 + ------I R2
(c) 2004 Fairchild Semiconductor Corporation
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OPTICALLY ISOLATED ERROR AMPLIFIER FOD2743A FOD2743B FOD2743C
OUTPUT CHARACTERISTICS (TA = 25C Unless otherwise specified.)
Parameter Collector dark current Emitter-collector voltage breakdown Collector-emitter voltage breakdown Test Conditions (VCE = 10 V) (Fig. 5) (IE = 100 A) (IC = 1.0mA) Symbol ICEO BVECO BVCEO 7 70 Min Typ 1 10 100 Max 50 Unit nA V V
TRANSFER CHARACTERISTICS (TA = 25C Unless otherwise specified.)
Parameter Current transfer ratio Collector-emitter saturation voltage Test Conditions (ILED = 1 mA, VCOMP = VFB, VCE = 5 V) (Fig. 6) Symbol CTR Min 50 Typ Max 100 0.4 Unit % V
(ILED = 1 mA, VCOMP = VFB, VCE (SAT) IC = 0.1 mA) (Fig. 6)
ISOLATION CHARACTERISTICS (TA = 25C Unless otherwise specified.)
Parameter Input-output insulation leakage current Withstand insulation voltage Resistance (input to output) Test Conditions (RH = 45%, TA = 25C, t = 5s, VI-O = 3000 VDC) (note. 1) (RH <= 50%, TA = 25C, t = 1 min) (notes. 1) VI-O = 500 VDC (note. 1) Symbol II-O VISO RI-O 5000 1012 Min Typ Max 1.0 Unit A Vrms Ohm
SWITCHING CHARACTERISTICS (TA = 25C Unless otherwise specified.)
Parameter Bandwidth Common mode transient immunity at output high Common mode transient immunity at output low Test Conditions (Fig. 7) (ILED = 0 mA, Vcm = 10 VPP RL = 2.2 k (Fig. 8) (note. 2) (ILED = 1 mA, Vcm = 10 VPP RL = 2.2 k (Fig. 8) (note. 2) Symbol BW CMH CML Min Typ 50 1.0 1.0 Max Unit kHZ kV/s kV/s
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.
(c) 2004 Fairchild Semiconductor Corporation
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OPTICALLY ISOLATED ERROR AMPLIFIER FOD2743A
I(LED) 1 VF 2 V 4 VREF 3 6 V R1 2 4 VCOMP R2 VREF 3 6 7 1 7
FOD2743B
I(LED)
FOD2743C
FIG. 1. VREF, VF, ILED (min) TEST CIRCUIT
FIG. 2. VREF/VCOMP TEST CIRCUIT
I(LED) 1 7
I(OFF) 1 7
IREF 2 V R1 3 3 4 6 V 2 V(LED) 4 6
FIG. 3. IREF TEST CIRCUIT
FIG. 4. I(OFF) TEST CIRCUIT
1
ICEO 7 VCE
I(LED) 1 7 VCE 2 V 4 VCOMP VREF 6
IC
2 4
6
3
3
FIG. 5. ICEO TEST CIRCUIT
FIG. 6. CTR, VCE(sat) TEST CIRCUIT
(c) 2004 Fairchild Semiconductor Corporation
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OPTICALLY ISOLATED ERROR AMPLIFIER FOD2743A FOD2743B FOD2743C
VCC = +5V DC IF = 1 mA RL 47
8
1
1f
VOUT
7
4
0.1 VPP
VIN 0.47V
6
2
5
3
Fig. 7 Frequency Response Test Circuit
VCC = +5V DC IF = 0 mA (A) IF = 1 mA (B) R1 2.2k VOUT
8
1
7
4
AB
6
2
5
3
_
VCM
+
10VP-P
Fig. 8 CMH and CML Test Circuit
(c) 2004 Fairchild Semiconductor Corporation
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OPTICALLY ISOLATED ERROR AMPLIFIER FOD2743A
TYPICAL PERFORMANCE CURVES
Fig. 9a - LED Current vs. Cathode Voltage
15 TA = 25C VCOMP = VFB ILED - Supply Current (mA) 1.0
FOD2743B
FOD2743C
Fig. 9b - LED Current vs. Cathode Voltage
TA = 25C VCOMP = VFB
10 ILED - Supply Current (mA) 0.5
5
0
0.0
-5
-0.5
-10
-15 -1 0 1 VCOMP - Cathode Voltage (V) 2 3
-1.0
-1
0
1 VCOMP - Cathode Voltage (V)
2
3
Fig. 10 - Reference Voltage Variation vs. Ambient Temperature
1.0 VREF - Reference Voltage Variation (%) 0.8 0.6 0.4 0.2 0.0 -0.2 -0.4 -0.6 -0.8 -1.0 -40 ILED = 1mA, 10mA Normalized to TA = 25C IREF - Reference Current (A) 4.0
Fig. 11 - Reference Current vs Ambient Temperature
ILED = 1mA, 10mA R1 = 10k 3.5
3.0
2.5
2.0
1.5
-20
0
20
40
60
80
100
1.0 -40
-20
0
20
40
60
80
100
TA - Ambient Temperature (C)
TA - Ambient Temperature (C)
Fig. 12 - Off-State Current vs. Ambient Temperature
100 VCC = 37V 20
Fig. 13 - Forward Current vs. Forward Voltage
IOFF - Off-State Current (nA)
10
IF - Forward Current (mA)
15
10 70C
25C 0C
5
1 -40 -20 0 20 40 60 80 100 0.9 1.0 1.1 1.2 1.3 1.4
TA - Ambient Temperature (C)
VF - Forward Voltage (V)
(c) 2004 Fairchild Semiconductor Corporation
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OPTICALLY ISOLATED ERROR AMPLIFIER FOD2743A
Fig. 14 - Dark Current vs. Ambient Temperature
10000 32 VCE = 10V 28 1000 ICEO - Dark Current (nA) IC - Collector Current (mA) ILED = 5, 10, 20mA 24 20 16 ILED = 10mA 12 8 4 0.1 -40 0 -40 ILED = 5mA 0.6 0.4 0.2 0.0 100 ILED = 20mA VCE = 5V 1.4 1.2 1.0 0.8 IC - Collector Current (mA) ILED = 1mA
FOD2743B
FOD2743C
1.6
Fig. 15 - Collector Current vs. Ambient Temperature
100
ILED = 1mA
10
1
-20
0
20
40
60
80
100
-20
TA - Ambient Temperature (C)
0 20 40 60 TA - Ambient Temperature (C)
80
Fig. 16 - Current Transfer Ratio vs. LED Current
160 VCE = 5V 140 (IC/IF) - Current Transfer Ratio (%) 120 100 80 -40C 60 70C 40 20 0 0.1 100C VCE(sat) - Saturation Voltage (V) 0.26 0.24 0.22 0.20 0.18 0.16 0.14 0.12 0.10 0.08
Fig. 17 - Saturation Voltage vs. Ambient Temperature
25C 0C
ILED = 10mA IC = 2.5mA ILED = 1mA IC = 0.1mA
1 10 ILED - Forward Current (mA)
0.06 -40
-20
0
20
40
60
80
100
TA - Ambient Temperature (C)
Fig. 18 - Collector Current vs. Collector Voltage
35 TA = 25C 30 IC - Collector Current (mA) 25 20 15 10 ILED = 5mA 5 ILED = 1mA 0 0 1 2 3 4 5 6 7 VCE - Collector-Emitter Voltage (V) 8 9 10 ILED = 10mA ILED = 20mA Delta Vref / Delta Vout ( mV/V) -0.34 -0.36 -0.38 -0.40 -0.42 -0.44 -0.32
Fig. 19 - Rate of Change Vref to Vout vs. Temperature
-0.46 -60
-40
-20
0
20
40
60
80
100
120
Temperature - C
(c) 2004 Fairchild Semiconductor Corporation
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OPTICALLY ISOLATED ERROR AMPLIFIER FOD2743A
5 VCC = 10V
FOD2743B
Fig. 20 - Voltage Gain vs. Frequency
FOD2743C
0 Voltage Gain - dB
IF = 10mA R L = 500 IF = 1mA RL = 2.4k IF = 10mA R L = 1k
-5
IF = 10mA RL = 100
-10
-15 1 10 100 Frequency - kHz 1000
Fig. 21 - Package Power Dissipation vs Ambient Temperature
200
Package Power Dissipation - mW
150
100
50
0 -40
-20
0
20
40
60
80
100
Ta - Ambient Temperature - C
(c) 2004 Fairchild Semiconductor Corporation
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OPTICALLY ISOLATED ERROR AMPLIFIER FOD2743A
The FOD2743
The FOD2743 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 KA431 shunt voltage regulator plus the CNY17F-X optocoupler.
FOD2743B
Compensation
FOD2743C
Powering the Secondary Side
The LED pin in the FOD2743 powers the secondary side, and in particular provides the current to run the LED. The actual structure of the FOD2743 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 2.5V + 1.2V = 3.7V. 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.
The compensation pin of the FOD2743 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 0.1F 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 FOD2743. 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 FAN4803, which has a 5V reference. If we select a 10k resistor for the LED, the maximum current the LED can see is (12V-4V) /10k = 800A. The CTR of the opto-isolator is a minimum of 50%, so the minimum collector current of the photo-transistor when the diode is full on is 400A. The collector resistor must thus be such that: 10V - 5V ----------------------------------- < 400A or R COLLECTOR > 12.5k; R COLLECTOR select 20k to allow some margin.
Feedback
Output voltage of a converter is determined by selecting a resistor divider from the regulated output to the FB pin. The FOD2743 attempts to regulate its FB pin to the reference voltage, 2.5V. The ratio of the two resistors should thus be: R TOP V OUT ------------------------- = -------------- - 1 R BOTTOM V REF The absolute value of the top resistor is set by the input offset current of 5.2A. To achieve 0.5% accuracy, the resistance of RTOP should be: V OUT - 2.5 ---------------------------- > 1040A R TOP
(c) 2004 Fairchild Semiconductor Corporation
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OPTICALLY ISOLATED ERROR AMPLIFIER FOD2743A FOD2743B FOD2743C
Package Dimensions (Through Hole)
Package Dimensions (Surface Mount)
0.390 (9.91) 0.370 (9.40)
4 3 2 1
PIN 1 ID.
4 3 2 1
PIN 1 ID.
0.270 (6.86) 0.250 (6.35)
5 6 7 8
0.270 (6.86) 0.250 (6.35)
5
6
7
8
0.390 (9.91) 0.370 (9.40)
SEATING PLANE
0.070 (1.78) 0.045 (1.14) 0.200 (5.08) 0.140 (3.55) 0.020 (0.51) MIN
0.070 (1.78) 0.045 (1.14) 0.020 (0.51) MIN
0.300 (7.62) TYP 0.016 (0.41) 0.008 (0.20)
0.154 (3.90) 0.120 (3.05) 0.022 (0.56) 0.016 (0.41) 0.100 (2.54) TYP 0.016 (0.40) 0.008 (0.20) 15 MAX 0.300 (7.62) TYP
0.022 (0.56) 0.016 (0.41) 0.100 (2.54) TYP Lead Coplanarity : 0.004 (0.10) MAX
0.045 [1.14] 0.315 (8.00) MIN 0.405 (10.30) MIN
Package Dimensions (0.4"Lead Spacing)
8 - Pin Dip
4
3
2
1
PIN 1 ID.
0.070 (1.78)
0.270 (6.86) 0.250 (6.35)
0.060 (1.52)
5
6
7
8
0.390 (9.91) 0.370 (9.40)
0.100 (2.54) 0.295 (7.49)
0.070 (1.78) 0.045 (1.14)
SEATING PLANE
0.415 (10.54)
0.030 (0.76)
0.200 (5.08) 0.140 (3.55)
0.004 (0.10) MIN
0.154 (3.90) 0.120 (3.05) 0.022 (0.56) 0.016 (0.41) 0.100 (2.54) TYP 0.016 (0.40) 0.008 (0.20) 0 to 15 0.400 (10.16) TYP
NOTE All dimensions are in inches (millimeters)
(c) 2004 Fairchild Semiconductor Corporation
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OPTICALLY ISOLATED ERROR AMPLIFIER FOD2743A
ORDERING INFORMATION Example: FOD2743A X
FOD2743B
Y
Y V: VDE tested
FOD2743C
X Packaging Option T: 0.4" Lead Spacing S: Surface Mount Lead Bend SD: Surface Mount Tape and Reel (1000 per reel)
MARKING INFORMATION
1
2743A V
3 4
2 6
XX YY B
5
Definitions
1 2 3 4 5 6 Fairchild logo Device number VDE mark (Note: Only appears on parts ordered with VDE option - See order entry table) Two digit year code, e.g., `03' Two digit work week ranging from `01' to `53' Assembly package code
(c) 2004 Fairchild Semiconductor Corporation
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OPTICALLY ISOLATED ERROR AMPLIFIER FOD2743A
Carrier Tape Specifications
FOD2743B
FOD2743C
K0
t
P0
P2
D0 E
A0 W1 B0
F W
d
User Direction of Feed
P
D1
Description Tape Width Tape Thickness Sprocket Hole Pitch Sprocket Hole Diameter Sprocket Hole Location Pocket Location Pocket Pitch Pocket Dimensions Cover Tape Width Cover Tape Thickness Max. Component Rotation or Tilt Min. Bending Radius
Symbol W t P0 D0 E F P2 P A0 B0 K0 W1 d R
Dimension in mm 16.0 0.3 0.30 0.05 4.0 0.1 1.55 0.05 1.75 0.10 7.5 0.1 4.0 0.1 12.0 0.1 10.30 0.20 10.30 0.20 4.90 0.20 1.6 0.1 0.1 max 10 30
(c) 2004 Fairchild Semiconductor Corporation
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OPTICALLY ISOLATED ERROR AMPLIFIER FOD2743A FOD2743B
Fig. 22 Recommended IR Reflow Profile Fig.21 Recommended IR Reflow Profile
* Peak reflow temperature * Time of temperature higher than 245C * Number of reflows 260 C (package surface temperature) 40 seconds or less Three
FOD2743C
300
10 s
250 Temperature (C)
260 245
200
150 40 s 100
50
50
100
150 Time (s)
200
250
(c) 2004 Fairchild Semiconductor Corporation
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OPTICALLY ISOLATED ERROR AMPLIFIER FOD2743A FOD2743B FOD2743C
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.
(c) 2004 Fairchild Semiconductor Corporation
Page 15 of 15
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