FOD2742A, FOD2742B, FOD2742C Optically Isolated Error Amplifier Features Description Optocoupler, precision reference and error amplifier in The FOD2742 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%. single package 2.5V reference CTR 100% to 200% 2,500V RMS isolation UL approval E90700, Volume 2 BSI approval 8661, 8662 VDE approval 136616 CSA approval 1113643 Low temperature coefficient 50 ppm/C max. FOD2742A: tolerance 0.5% FOD2742B: tolerance 1% FOD2742C: tolerance 2% Applications Power supplies regulation 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 converters. When using the FOD2742, 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 small outline package. DC to DC converters Schematic NC 1 Package Outline 8 LED C 2 7 FB E 3 6 COMP NC 4 (c)2003 Fairchild Semiconductor Corporation FOD2742A, FOD2742B, FOD2742C Rev. 1.0.1 5 GND www.fairchildsemi.com FOD2742A, FOD2742B, FOD2742C -- Optically Isolated Error Amplifier April 2009 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. Typical Application V1 FAN4803 PWM Control VO FOD2742 2 8 6 3 7 5 (c)2003 Fairchild Semiconductor Corporation FOD2742A, FOD2742B, FOD2742C Rev. 1.0.1 R1 R2 www.fairchildsemi.com 2 FOD2742A, FOD2742B, FOD2742C -- Optically Isolated Error Amplifier Pin Definitions 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. Symbol Parameter Value Units TSTG Storage Temperature -40 to +125 C TOPR Operating Temperature -25 to +85 C Reflow Temperature Profile (refer to 15) VLED Input Voltage 37 V ILED Input DC Current 20 mA VCEO Collector-Emitter Voltage 70 V VECO Emitter-Collector Voltage 7 V Collector Current 50 mA PD1 IC Input Power Dissipation(1) 145 mW PD2 Transistor Power Dissipation(2) 85 mW 145 mW PD3 Total Power Dissipation(3) Notes: 1. Derate linearly from 25C at a rate of 2.42mW/C 2. Derate linearly from 25C at a rate of 1.42mW/C. 3. Derate linearly from 25C at a rate of 2.42mW/C. (c)2003 Fairchild Semiconductor Corporation FOD2742A, FOD2742B, FOD2742C Rev. 1.0.1 www.fairchildsemi.com 3 FOD2742A, FOD2742B, FOD2742C -- Optically Isolated Error Amplifier Absolute Maximum Ratings (TA = 25C unless otherwise specified) Input Characteristics Symbol VF VREF Parameter Device Min. LED Forward Voltage ILED = 10mA, VCOMP = VFB (Fig. 1) All Reference Voltage ILED = 10mA, VCOMP = VFB (Fig. 1) A B C VREF (DEV) Deviation of VREF Over Temperature VRE VCOMP Test Conditions TA = -25C to +85C (Fig. 1) Ratio of VREF Variation to the Output of the Error Amplifier ILED = 10mA (Fig. 2) VCOMP = 10V to VREF All All VCOMP = 36V to 10V Typ. Max. Unit 1.20 1.5 V 2.482 2.495 2.508 V 2.470 2.495 2.520 V 2.450 2.500 2.550 V 3.5 17 mV -0.5 -2.7 -0.3 -2.0 mV/ V Feedback Input Current ILED = 10mA, R1 = 10K (Fig. 3) All 2.2 4 A IREF (DEV) Deviation of IREF Over Temperature TA = -25C to +85C (Fig. 3) All 1.0 1.2 A ILED (MIN) Minimum Drive Current VCOMP = VFB (Fig. 1) All 0.45 1.0 mA I(OFF) Off-state Error Amplifier Current VLED = 37V, VFB = 0 (Fig. 4) All 0.01 1.0 A |ZOUT| Error Amplifier Output Impedance (see note 2) VCOMP = VREF, ILED = 1mA to 20mA, f 1.0kHz All 0.15 0.5 IREF Notes: 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: 6 { V REF ( DEV ) /V REF ( T A = 25C ) } x 10 V REF ( ppm/C ) = ---------------------------------------------------------------------------------------------------T A 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)2003 Fairchild Semiconductor Corporation FOD2742A, FOD2742B, FOD2742C Rev. 1.0.1 www.fairchildsemi.com 4 FOD2742A, FOD2742B, FOD2742C -- Optically Isolated Error Amplifier Electrical Characteristics (TA = 25C unless otherwise specified) Output Characteristics Symbol ICEO Parameter Test Conditions Min. Typ. Max. Unit 1 50 nA Collector Dark Current VCE = 10V (Fig. 5) BVECO Emitter-Collector Voltage Breakdown IE = 100A 7 10 V BVCEO Collector-Emitter Voltage Breakdown IC = 1.0mA 70 120 V Min. Typ. Max. Unit 100 140 200 % 0.16 0.4 V Typ. Max. Unit 1.0 A 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) Isolation Characteristics Symbol Parameter Test Conditions Input-Output Insulation Leakage Current RH = 45%, TA = 25C, t = 5s, VI-O = 3000 VDC (Note 1) VISO Withstand Insulation Voltage RH 50%, TA = 25C, t = 1 min. (Note 1) RI-O Resistance (Input to Output) VI-O = 500 VDC (Note 1) II-O Min. 2500 Vrms 1012 Switching Characteristics Symbol BW Parameter Test Conditions Min. Typ. Max. Unit Bandwidth Fig. 7 50 kHz CMH Common Mode Transient Immunity at Output HIGH ILED = 0mA, Vcm = 10 VPP RL = 2.2k (Fig. 8) (Note 2) 1.0 kV/s CML Common Mode Transient Immunity at Output LOW ILED = 10mA, Vcm = 10 VPP RL = 2.2k (Fig. 8) (Note 2) 1.0 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)2003 Fairchild Semiconductor Corporation FOD2742A, FOD2742B, FOD2742C Rev. 1.0.1 www.fairchildsemi.com 5 FOD2742A, FOD2742B, FOD2742C -- Optically Isolated Error Amplifier Electrical Characteristics (TA = 25C unless otherwise specified) (Continued) 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 8 2 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 (c)2003 Fairchild Semiconductor Corporation FOD2742A, FOD2742B, FOD2742C Rev. 1.0.1 Figure 6. CTR, VCE(sat) Test Circuit www.fairchildsemi.com 6 FOD2742A, FOD2742B, FOD2742C -- Optically Isolated Error Amplifier Test Circuits VCC = +5V DC IF = 10 mA RL 1 47 8 1f 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 2.2k VOUT 1 8 2 7 3 6 4 5 _ A B VCM + 10VP-P Figure 8. CMH and CML Test Circuit (c)2003 Fairchild Semiconductor Corporation FOD2742A, FOD2742B, FOD2742C Rev. 1.0.1 www.fairchildsemi.com 7 FOD2742A, FOD2742B, FOD2742C -- Optically Isolated Error Amplifier Test Circuits (Continued) Fig. 9a LED Current vs. Cathode Voltage Fig. 9b LED Current vs. Cathode Voltage 1.0 TA = 25C VCOMP = VFB 10 ILED - SUPPLY CURRENT (mA) ILED - SUPPLY CURRENT (mA) 15 5 0 -5 -10 -15 0.5 0.0 -0.5 -1.0 -1 0 1 3 2 TA = 25C VCOMP = VFB -1 0 VCOMP - CATHODE VOLTAGE (V) 1 3 2 VCOMP - CATHODE VOLTAGE (V) Fig. 10 Reference Voltage vs. Ambient Temperature Fig. 11 Reference Current vs Ambient Temperature 2.510 ILED = 10mA IREF - REFERENCE CURRENT (A) VREF - REFERENCE VOLTAGE (V) 2.508 ILED = 10mA R1 = 10k 2.506 2.504 2.502 2.500 2.498 2.496 2.494 3 2 2.492 2.490 -40 -20 0 20 40 60 80 -40 100 -20 0 20 40 60 80 100 TA - AMBIENT TEMPERATURE(C) TA - AMBIENT TEMPERATURE (C) Fig. 12 Off-State Current vs. Ambient Temperature Fig. 13 Forward Current vs. Forward Voltage 20 IF - FORWARD CURRENT (mA) IOFF - OFF-STATE CURRENT (nA) VLED = 37V 100 10 1 -40 -20 0 20 40 60 80 25C 10 0C 70C 5 0.9 100 1.0 1.1 1.2 1.3 1.4 VF - FORWARD VOLTAGE (V) TA - AMBIENT TEMPERATURE (C) (c)2003 Fairchild Semiconductor Corporation FOD2742A, FOD2742B, FOD2742C Rev. 1.0.1 15 www.fairchildsemi.com 8 FOD2742A, FOD2742B, FOD2742C -- Optically Isolated Error Amplifier Typical Performance Curves Fig. 15 Collector Current vs. Ambient Temperature Fig. 14 Dark Current vs. Ambient Temperature 30 VCE = 10V VCE = 5V IC - COLLECTOR CURRENT (mA) ICEO - DARK CURRENT (nA) 1000 100 10 1 25 ILED = 20mA 20 ILED = 10mA 15 10 ILED = 5mA 5 ILED = 1mA 0 0.1 -40 -20 0 20 40 60 80 0 100 10 20 Fig. 16 Current Transfer Ratio vs. LED Current 50 60 70 80 90 100 Fig. 17 Saturation Voltage vs. Ambient Temperature 0.26 160 VCE = 5V VCE(sat) - SATURATION VOLTAGE (V) (IC/IF) - CURRENT TRANSFER RATIO (%) 40 TA - AMBIENT TEMPERATURE (C) TA - AMBIENT TEMPERATURE (C) 0C 140 25C 120 70C 100 80 60 1 10 ILED - FORWARD CURRENT (mA) 0.24 100 ILED = 10mA IC = 2.5mA 0.22 0.20 0.18 0.16 0.14 0.12 0.10 -40 40 -20 0 20 40 60 80 100 TA - AMBIENT TEMPERATURE (C) Fig. 19 Rate of Change Vref to Vout vs. Temperature Fig. 18 Collector Current vs. Collector Voltage 35 -0.22 TA = 25C -0.24 30 ILED = 20mA -0.26 25 Vref /Vout ( mV/V) IC - COLLECTOR CURRENT (mA) 30 20 ILED = 10mA 15 10 ILED = 5mA -0.28 -0.30 -0.32 -0.34 -0.36 -0.38 -0.40 5 -0.42 ILED = 1mA 0 0 1 2 3 4 5 6 7 8 VCE - COLLECTOR-EMITTER VOLTAGE (V) (c)2003 Fairchild Semiconductor Corporation FOD2742A, FOD2742B, FOD2742C Rev. 1.0.1 9 -0.44 -40 10 -20 0 20 40 60 80 100 TEMPERATURE (C) www.fairchildsemi.com 9 FOD2742A, FOD2742B, FOD2742C -- Optically Isolated Error Amplifier Typical Performance Curves (Continued) FOD2742A, FOD2742B, FOD2742C -- Optically Isolated Error Amplifier Typical Performance Curves (Continued) Fig. 20 Voltage Gain vs. Frequency VOLTAGE GAIN (dB) 5 VCC = 10V IF = 10mA 0 RL = 100 RL = 500 -5 RL = 1k -10 -15 1 (c)2003 Fairchild Semiconductor Corporation FOD2742A, FOD2742B, FOD2742C Rev. 1.0.1 10 100 FREQUENCY (kHz) 1000 www.fairchildsemi.com 10 Compensation The FOD2742 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. The compensation pin of the FOD2742 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. Powering the Secondary Side The LED pin in the FOD2742 powers the secondary side, and in particular provides the current to run the LED. The actual structure of the FOD2742 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 + 1.5V = 4.0V. 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. 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. 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. Photo-Transistor The Photo-transistor is the output of the FOD2742. In a normal configuration the collector will be attached to a pull-up resistor and the emitter grounded. There is no base connection necessary. Feedback Output voltage of a converter is determined by selecting a resistor divider from the regulated output to the FB pin. The FOD2742 attempts to regulate its FB pin to the reference voltage, 2.5V. The ratio of the two resistors should thus be: 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. R TOP V OUT ------------------------- = --------------1 R BOTTOM V REF 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 10KV resistor for the LED, the maximum current the LED can see is: 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: (12V-4V) /10K = 800A. V OUT - 2.5 ----------------------------- > 1040A R TOP The CTR of the opto-isolator is a minimum of 100%, so the minimum collector current of the photo-transistor when the diode is full on is also 800A. The collector resistor must thus be such that: 10V - 5V ----------------------------------- < 800A or R COLLECTOR > 6.25K; R COLLECTOR select 12K to allow some margin. (c)2003 Fairchild Semiconductor Corporation FOD2742A, FOD2742B, FOD2742C Rev. 1.0.1 www.fairchildsemi.com 11 FOD2742A, FOD2742B, FOD2742C -- Optically Isolated Error Amplifier The FOD2742 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. Drawings may change in any manner without notice. Please note the revision and/or date on the drawing and contact a Fairchild Semiconductor representative to verify or obtain the most recent revision. Package specifications do not expand the terms of Fairchild's worldwide terms and conditions, specifically the warranty therein, which covers Fairchild products. Always visit Fairchild Semiconductor's online packaging area for the most recent package drawings: http://www.fairchildsemi.com/packaging/ (c)2003 Fairchild Semiconductor Corporation FOD2742A, FOD2742B, FOD2742C Rev. 1.0.1 www.fairchildsemi.com 12 FOD2742A, FOD2742B, FOD2742C -- Optically Isolated Error Amplifier Package Dimensions FOD2742A, FOD2742B, FOD2742C -- Optically Isolated Error Amplifier Ordering Information Option Order Entry Identifier V V R2 R2 R2V R2V Description VDE 0884 Tape and reel (2500 units per reel) VDE 0884, Tape and reel (2500 units per reel) Marking Information 1 2742A V X YY S 3 4 2 6 5 Definitions 1 Fairchild logo 2 Device number 3 VDE mark (Note: Only appears on parts ordered with VDE option - See order entry table) 4 One digit year code, e.g., `3' 5 Two digit work week ranging from `01' to `53' 6 Assembly package code (c)2003 Fairchild Semiconductor Corporation FOD2742A, FOD2742B, FOD2742C Rev. 1.0.1 www.fairchildsemi.com 13 8.0 0.10 2.0 0.05 3.50 0.20 0.30 MAX O1.5 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 O1.5 0.1 User Direction of Feed Dimensions in mm (c)2003 Fairchild Semiconductor Corporation FOD2742A, FOD2742B, FOD2742C Rev. 1.0.1 www.fairchildsemi.com 14 FOD2742A, FOD2742B, FOD2742C -- Optically Isolated Error Amplifier Carrier Tape Specifications FOD2742A, FOD2742B, FOD2742C -- 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 = 3C/S Max. Ramp-down Rate = 6C/S tP Tsmax tL Preheat Area Tsmin ts 120 240 360 Time 25C to Peak Time (seconds) Profile Freature Pb-Free Assembly Profile Temperature Min. (Tsmin) 150C Temperature Max. (Tsmax) 200C Time (tS) from (Tsmin to Tsmax) 60-120 seconds Ramp-up Rate (tL to tP) 3C/second max. Liquidous Temperature (TL) 217C Time (tL) Maintained Above (TL) 60-150 seconds Peak Body Package Temperature 260C +0C / -5C Time (tP) within 5C of 260C 30 seconds Ramp-down Rate (TP to TL) 6C/second max. Time 25C to Peak Temperature (c)2003 Fairchild Semiconductor Corporation FOD2742A, FOD2742B, FOD2742C Rev. 1.0.1 8 minutes max. www.fairchildsemi.com 15 Auto-SPMTM Build it NowTM CorePLUSTM CorePOWERTM CROSSVOLTTM CTLTM Current Transfer LogicTM EcoSPARK(R) EfficentMaxTM EZSWITCHTM* TM* (R) (R) Fairchild Fairchild Semiconductor(R) FACT Quiet SeriesTM FACT(R) (R) FAST FastvCoreTM FETBenchTM FlashWriter(R)* FPSTM F-PFSTM FRFET(R) SM Global Power Resource Green FPSTM Green FPSTM e-SeriesTM GmaxTM GTOTM IntelliMAXTM ISOPLANARTM MegaBuckTM MICROCOUPLERTM MicroFETTM MicroPakTM MillerDriveTM MotionMaxTM Motion-SPMTM OPTOLOGIC(R) OPTOPLANAR(R) (R) PDP SPMTM Power-SPMTM PowerTrench(R) PowerXSTM Programmable Active DroopTM QFET(R) QSTM Quiet SeriesTM RapidConfigureTM TM Saving our world, 1mW/W/kW at a timeTM SmartMaxTM SMART STARTTM SPM(R) STEALTHTM SuperFETTM SuperSOTTM-3 SuperSOTTM-6 SuperSOTTM-8 SupreMOSTM SyncFETTM Sync-LockTM (R) * The Power Franchise(R) TinyBoostTM TinyBuckTM TinyLogic(R) TINYOPTOTM TinyPowerTM TinyPWMTM TinyWireTM TriFault DetectTM TRUECURRENTTM* SerDesTM UHC(R) Ultra FRFETTM UniFETTM VCXTM VisualMaxTM XSTM * Trademarks of System General Corporation, used under license by Fairchild Semiconductor. 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Datasheet contains specifications on a product that is discontinued by Fairchild Semiconductor. The datasheet is for reference information only. Rev. I40 (c)2003 Fairchild Semiconductor Corporation FOD2742A, FOD2742B, FOD2742C Rev. 1.0.1 www.fairchildsemi.com 16 FOD2742A, FOD2742B, FOD2742C -- Optically Isolated Error Amplifier TRADEMARKS The following includes registered and unregistered trademarks and service marks, owned by Fairchild Semiconductor and/or its global subsidiaries, and is not intended to be an exhaustive list of all such trademarks.