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FOD2712A — Optically Isolated Error Ampliﬁer

FOD2712A Rev. 1.0.1

December 2010

FOD2712A

Optically Isolated Error Amplifier

Features

■

Optocoupler, precision reference and error amplifier in

single package

■

1.240V ± 1% reference

■

CTR 100% to 200%

■

2,500V RMS isolation

■

UL approval E90700

Applications

■

Power system for workstations

■

Telecom central office supply

■

Telecom bricks

Description

The FOD2712A Optically Isolated Amplifier consists of

the popular AZ431L precision programmable shunt ref-

erence and an optocoupler. The optocoupler is a gallium

arsenide (GaAs) light emitting diode optically coupled to

a silicon phototransistor. The reference voltage toler-

ance 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 FOD2712A, power supply designers can

reduce the component count and save space in tightly

packaged designs. The tight tolerance reference elimi-

nates the need for adjustments in many applications.

The device comes in a compact 8-pin small outline

package.

Schematic Package Outline

4 5

LED

COMP

GND

Summary of content (16 pages)

PAGE 1
FOD2712A Optically Isolated Error Amplifier Features Description ■ Optocoupler, precision reference and error amplifier in The FOD2712A Optically Isolated Amplifier consists of the popular AZ431L 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%. ■ ■ ■ ■ single package 1.
PAGE 2
Pin Number Pin Name 1 NC 2 C Phototransistor Collector 3 E Phototransistor Emitter 4 NC 5 GND 6 COMP 7 FB 8 LED Functional Description Not connected 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.
PAGE 3
Stresses exceeding the absolute maximum ratings may damage the device. The device may not function or be operable above the recommended operating conditions and stressing the parts to these levels is not recommended. In addition, extended exposure to stresses above the recommended operating conditions may affect device reliability. The absolute maximum ratings are stress ratings only.
PAGE 4
Input Characteristics Symbol VF VREF Parameter LED Forward Voltage ILED = 10mA, VCOMP = VFB (Fig.1) Reference Voltage -40°C to +85°C 25°C VCOMP = VFB, ILED = 10mA (Fig.1) VREF (DEV) Deviation of VREF over temperature See Note 1 ∆VREF ∆VCOMP Test Conditions Min. 1.221 1.228 TA = -40 to +85°C Ratio of Vref Variation to the Output of the ILED = 10 mA, Error Amplifier VCOMP = VREF to 12V (Fig. 2) Typ. Max. Unit 1.5 V 1.259 V 1.240 1.252 4 12 mV -1.5 -2.
PAGE 5
Output Characteristics Symbol ICEO Parameter Test Conditions Min. Typ. Max. Unit 50 nA Collector Dark Current VCE = 10V (Fig. 5) BVCEO Collector-Emitter Voltage Breakdown IC = 1.0mA 70 V BVECO Emitter-Collector Voltage Breakdown IE = 100µA 7 V Transfer Characteristics Symbol CTR VCE (SAT) Parameter Test Conditions Current Transfer Ratio ILED = 10mA, VCOMP = VFB, VCE = 5V (Fig. 6) Collector-Emitter Saturation Voltage ILED = 10mA, VCOMP = VFB, IC = 2.5mA (Fig. 6) Min. Typ.
PAGE 6
I(LED) I(LED) 8 8 2 2 VF 6 R1 3 V 7 V 6 3 7 VCOMP R2 VREF VREF 5 5 Figure 2. ∆VREF/∆VCOMP Test Circuit Figure 1. VREF, VF, ILED (min) Test Circuit I(LED) I(OFF) 8 2 8 2 IREF 6 6 3 7 V 3 V(LED) 7 V R1 5 5 Figure 4. I(OFF) Test Circuit Figure 3. IREF Test Circuit 8 I(LED) ICEO 8 2 VCE 6 I(C) 2 VCE 6 3 7 V 3 7 VCOMP VREF 5 5 Figure 5. ICEO Test Circuit ©2010 Fairchild Semiconductor Corporation FOD2712A Rev. 1.0.1 Figure 6. CTR, VCE(sat) Test Circuit www.
PAGE 7
VCC = +5V DC IF = 10 mA RL 1 47Ω 8 1µf VOUT 2 7 VIN 0.47V 0.1 VPP 3 6 4 5 Figure 7. Frequency Response Test Circuit VCC = +5V DC IF = 0 mA (A) IF = 10 mA (B) R1 2.2kΩ VOUT 1 8 2 7 3 6 4 5 _ A B VCM + 10VP-P Figure 8. CMH and CML Test Circuit ©2010 Fairchild Semiconductor Corporation FOD2712A Rev. 1.0.1 www.fairchildsemi.
PAGE 8
Fig. 9a LED Current vs. Cathode Voltage Fig. 9b LED Current vs. Cathode Voltage 10 150 TA = 25°C VCOMP = VFB ILED – SUPPLY CURRENT (µA) ILED – SUPPLY CURRENT (mA) 15 5 0 -5 -10 120 TA = 25°C VCOMP = VFB 90 60 30 0 -30 -60 -90 -120 -15 -1.0 -0.5 0.0 0.5 1.0 -150 -1.0 1.5 -0.5 VCOMP – CATHODE VOLTAGE (V) Fig. 10 Reference Voltage vs. Ambient Temperature 1.0 1.5 350 IREF – REFERENCE CURRENT (nA) ILED = 10mA VREF – REFERENCE VOLTAGE (V) 0.5 Fig. 11 Reference Current vs.
PAGE 9
Fig.13 LED Forward Current vs. Forward Voltage Fig.14 Dark Current vs. Temperature VCE = 10V 1000 ICEO – DARK CURRENT (nA) ILED – FORWARD CURRENT (mA) 20 15 70°C 10 25°C 0°C 5 0 0.95 100 10 1 0.1 1.00 1.05 1.10 1.15 1.20 1.25 1.30 1.35 -40 -20 0 VF – FORWARD VOLTAGE (V) Fig. 15 Collector Current vs.
PAGE 10
Fig. 19 Delta VREF/Delta VCOMP vs. Ambient Temperature Fig. 18 Collector Current vs. Collector Voltage 1 TA = 25°C 40 DELTA VREF/DELTA VCOMP (mV/V) IC – COLLECTOR CURRENT (mA) 45 35 ILED = 20 mA 30 25 20 ILED = 10 mA 15 10 ILED = 5 mA 5 0 -1 ILED = 1 mA -2 -40 0 0 1 2 3 4 5 6 7 8 9 10 -20 VCE – COLLECTOR-EMITTER VOLTAGE (V) 0 20 40 60 80 100 TA – AMBIENT TEMPERATURE (°C) Fig. 20 Voltage Gain vs.
PAGE 11
Compensation The FOD2712A 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 AZ431L shunt voltage regulator plus the CNY17F-3 optocoupler. The compensation pin of the FOD2712A provides the opportunity for the designer to design the frequency response of the converter.
PAGE 12
8-pin SOIC Surface Mount 8 0.164 (4.16) 0.144 (3.66) SEATING PLANE 1 0.202 (5.13) 0.182 (4.63) 0.010 (0.25) 0.006 (0.16) 0.143 (3.63) 0.123 (3.13) 0.021 (0.53) 0.011 (0.28) 0.008 (0.20) 0.003 (0.08) 0.244 (6.19) 0.224 (5.69) 0.050 (1.27) Typ. Lead Coplanarity: 0.004 (0.10) MAX Recommended Pad Layout 0.024 (0.61) 0.060 (1.52) 0.275 (6.99) 0.155 (3.94) 0.050 (1.27) Dimensions in inches (mm). Package drawings are provided as a service to customers considering Fairchild components.
PAGE 13
FOD2712A — Optically Isolated Error Amplifier Ordering Information Option Example Part Number V FOD2712AV R2 FOD2712AR2 R2V FOD2712AR2V Description VDE 0884 Tape and reel (2500 units per reel) VDE 0884, Tape and reel (2500 units per reel) Marking Information 1 2712A V X YY S 3 4 2 6 5 Definitions ©2010 Fairchild Semiconductor Corporation FOD2712A Rev. 1.0.
PAGE 14
8.0 ± 0.10 2.0 ± 0.05 3.50 ± 0.20 0.30 MAX Ø1.5 MIN 1.75 ± 0.10 4.0 ± 0.10 5.5 ± 0.05 8.3 ± 0.10 5.20 ± 0.20 0.1 MAX 6.40 ± 0.20 12.0 ± 0.3 Ø1.5 ± 0.1 User Direction of Feed Dimensions in mm ©2010 Fairchild Semiconductor Corporation FOD2712A Rev. 1.0.1 www.fairchildsemi.
PAGE 15
FOD2712A — Optically Isolated Error Amplifier Reflow Profile Temperature (°C) TP 260 240 TL 220 200 180 160 140 120 100 80 60 40 20 0 Max. Ramp-up Rate = 3°C/S Max. Ramp-down Rate = 6°C/S tP Tsmax tL Preheat Area Tsmin ts 120 240 360 Time 25°C to Peak Time (seconds) Profile Freature Pb-Free Assembly Profile Temperature Min. (Tsmin) 150°C Temperature Max. (Tsmax) 200°C Time (tS) from (Tsmin to Tsmax) 60–120 seconds Ramp-up Rate (tL to tP) 3°C/second max.
PAGE 16
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