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4/8/04 optically isolated error amplifier p age 1 of 15 fod2743a fod2743b fod2743c ? 2004 fairchild semiconductor corporation description the fod2743 optically isolated ampli?er 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 gr ades 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 coef?cient of 50 ppm/c. it is primarily intended for use as the error ampli?er/ reference voltage/optocoupler function in isolated ac to dc power supplies and dc/dc con- ve r ters. 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 f or adjustments in many applications. the device comes in a 8-pin dip white package. features ? optocoupler, precision reference and error ampli?er 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 ?l ow temperature coef?cient 50 ppm/c max ? fod2743a: tolerance 0.5% fod2743b: tolerance 1% fod2743c: tolerance 2% applications ?p ow er supplies regulation ? dc to dc converters * the compensation network must be attached between pins 2 and 4. pin definitions pin number pin name pin function description 1 led anode led. this pin is the input to the light emitting diode. 2 comp error ampli?er compensation. this pin is the output of the error ampli?er. * 3 gnd ground 4f bv oltage feedback. this pin is the inverting input to the error ampli?er 5n c not connected 6e phototransistor emitter 7c phototransistor collector 8n c not connected 8 8 1 8 1 1 functional block diagram 1 2 3 4 5 6 7 8 nc c e nc led comp gnd fb
4/8/04 p age 2 of 15 ? 2004 fairchild semiconductor corporation optically isolated error amplifier fod2743a fod2743b fod2743c typical application v o v 1 r1 r2 7 6 1 2 4 3 pwm control f an4803 fod2743 notes 1. see derating graph ?g 21. 2. functional operation under these conditions is not implied. permanent damage may occur if the device is subjected to conditio ns outside these ratings. absolute maximum ratings (t a = 25c unless otherwise speci?ed.) p arameter symbol value units storage temperature t stg -40 to +125 c operating temperature t opr -25 to +85 c lead solder temperature t sol 260 for 10 sec. c input voltage v led 37 v input dc current i led 20 ma collector-emitter voltage v ceo 70 v emitter-collector voltage v eco 7v collector current i c 50 ma input power dissipation pd1 145 mw tr ansistor power dissipation pd2 85 mw t otal power dissipation (note 1) pd3 145 mw
4/8/04 p age 3 of 15 ? 2004 fairchild semiconductor corporation optically isolated error amplifier fod2743a fod2743b fod2743c 1. the deviation parameters v ref(dev) and i ref(dev) are de?ned as the differences between the maximum and minimum values obtained over the rated temperature range. the average full-range temperature coef?cient of the reference input voltage, ? v ref , is de?ned as: where ? t a is the rated operating free-air temperature range of the device. 2. the dynamic impedance is de?ned 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: electrical characteristics (t a = 25c unless otherwise speci?ed.) input characteristics p arameter test conditions symbol device min. typ. max. unit led forward voltage (i led = 1 ma, v comp = v fb ) (?g.1) v f all 1.07 1.2 v reference voltage i led = 1 ma, v comp = v fb v ref a 2.482 2.495 2.508 v b 2.470 2.495 2.520 v c 2.450 2.500 2.550 v deviation of v ref over temperature t a = -25c to +85c v ref (dev) all 4.5 17 mv ratio of v ref variation to the output of the error ampli?er i led = 1 ma ? v comp = 10v to v ref ? v ref / ? v comp all -0.4 -2.7 mv/ v ? v comp = 36v to 10v -0.3 -2.0 f eedback input current i led = 1ma, r 1 = 10k ? (?g 3) i ref all 2 4 a deviation of i ref over temperature t a = -25c to +85c i ref (dev) all 1 1.2 a minimum drive current v comp = v fb (?g.1) i led (min) all 0.45 1.0 ma off-state error ampli?er current v led = 37v, v fb = 0 (?g 4.) i (off) all 0.001 1.0 a error ampli?er output impedance (see note 2) v comp = v ref , i led = 1ma to 20ma, f 1.0 khz |z out | all 0.15 0.5 ? ? v ref ppm/c () v ref dev () /v ref t a 25c = () {} 10 6 ? t a ---------------------------------------------------------------------------------------------------- - = z out, tot = ? v ? i ------- -z out 1 r1 r2 ------- - +
4/8/04 p age 4 of 15 ? 2004 fairchild semiconductor corporation optically isolated error amplifier fod2743a fod2743b fod2743c 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 togethe r. 2. common mode transient immunity at output high is the maximum tolerable (positive) dvcm/dt on the leading edge of the com- mon 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. output characteristics (t a = 25c unless otherwise speci?ed.) p arameter test conditions symbol min typ max unit collector dark current (v ce = 10 v) (fig. 5) i ceo 150na emitter-collector voltage breakdown (i e = 100 a) bv eco 710 v collector-emitter voltage breakdown (i c = 1.0ma) bv ceo 70 100 v transfer characteristics (t a = 25c unless otherwise speci?ed.) p arameter test conditions symbol min typ max unit current transfer ratio (i led = 1 ma, v comp = v fb , v ce = 5 v) (fig. 6) ctr 50 100 % collector-emitter saturation voltage (i led = 1 ma, v comp = v fb, i c = 0.1 ma) (fig. 6) v ce (sat) 0.4 v isolation characteristics (t a = 25c unless otherwise speci?ed.) p arameter test conditions symbol min typ max unit input-output insulation leakage current (rh = 45%, t a = 25c, t = 5s, v i-o = 3000 vdc) (note. 1) i i-o 1.0 a withstand insulation v oltage (rh <= 50%, t a = 25c, t = 1 min) (notes. 1) v iso 5000 vrms resistance (input to output) v i-o = 500 vdc (note. 1) r i-o 10 12 ohm switching characteristics (t a = 25c unless otherwise speci?ed.) p arameter test conditions symbol min typ max unit bandwidth (fig. 7) bw 50 khz common mode transient immunity at output high (i led = 0 ma, ? vcm ? = 10 v pp rl = 2.2 k ? (fig. 8) (note. 2) ? cmh ? 1.0 kv/s common mode transient immunity at output low (i led = 1 ma, ? vcm ? = 10 v pp rl = 2.2 k ? (fig. 8) (note. 2) ? cml ? 1.0 kv/s
4/8/04 p age 5 of 15 ? 2004 fairchild semiconductor corporation optically isolated error amplifier fod2743a fod2743b fod2743c i (led) v (led) v comp v comp i ceo v ce v ref v ce i (led) v f v ref v ref 17 6 7 6 v v v 2 4 3 i (led) i (led) i c i (off) i ref 1 2 7 6 7 6 7 6 v v 4 3 1 2 4 3 1 2 4 3 1 2 7 6 4 3 r1 1 2 r1 r2 4 3 fig. 1. v ref , v f, i led (min) test circuit fig. 3. i ref test circuit fig. 5. i ceo test circuit fig. 6. ctr, v ce(sat) test circuit fig. 4. i (off) test circuit fig. 2. ? v ref/ ? v comp test circuit
4/8/04 p age 6 of 15 ? 2004 fairchild semiconductor corporation optically isolated error amplifier fod2743a fod2743b fod2743c 6 7 8 5 1 4 2 a b 3 6 5 7 8 2 3 4 1 v cc = +5v dc v cc = +5v dc i f = 1 ma i f = 0 ma (a) i f = 1 ma (b) v in 0.47v 0.1 v pp 47 ? v out v out vcm 10v p-p r1 2.2k ? r l 1 f + _ fig. 7 frequency response test circuit fig. 8 cmh and cml test circuit
4/8/04 p age 7 of 15 ? 2004 fairchild semiconductor corporation optically isolated error amplifier fod2743a fod2743b fod2743c typical performance curves fig. 10 ?reference voltage variation vs. ambient temperature ? v ref - reference voltage variation (%) t a = 25c v comp = v fb t a - ambient temperature (c) t a - ambient temperature (c) fig. 9a ?led current vs. cathode voltage i led - supply current (ma) i led - supply current (ma) i ref - reference current (a) -15 -10 -5 0 5 10 15 -1 0 1 2 v comp - cathode voltage (v) 3 fig. 9b ?led current vs. cathode voltage fig. 11 ?reference current vs ambient temperature -1.0 -0.5 0.0 0.5 1.0 -1 0 1 2 v comp - cathode voltage (v) 3 t a = 25c v comp = v fb t a - ambient temperature (c) -40 -20 0 20 40 60 80 100 i off - off-state current (na) 1 10 100 fig. 12 ?off-state current vs. ambient temperature v cc = 37v v f - forward voltage (v) i f - forward current (ma) 5 0.9 1.0 1.1 1.2 70c 25c 0c 1.3 1.4 10 15 20 fig. 13 ?forward current vs. forward voltage -40 -20 0 20 40 60 80 100 -40 -20 0 20 40 60 80 100 1.0 1.5 2.0 2.5 3.0 3.5 4.0 i led = 1ma, 10ma r1 = 10k? -1.0 -0.8 -0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 0.8 1.0 i led = 1ma, 10ma normalized to t a = 25c
4/8/04 p age 8 of 15 ? 2004 fairchild semiconductor corporation optically isolated error amplifier fod2743a fod2743b fod2743c t a - ambient temperature ( c) t a - ambient temperature ( c) vce - collector-emitter voltage (v) i led - forward current (ma) 0.1 1 10 (i c /i f ) - current transfer ratio (%) 20 0 40 60 80 100 120 140 160 i c - collector current (ma) i led = 5, 10, 20ma -40 -20 0 20 40 60 80 100 i ceo - dark current (na) 0.1 1 10 100 1000 10000 012345678910 i c - collector current (ma) 0 5 10 15 20 25 30 35 fig. 15 ?collector current vs. ambient temperature fig. 14 ?dark current vs. ambient temperature fig. 18 ?collector current vs. collector voltage fig. 16 ?current transfer ratio vs. led current v ce = 10v t a = 25 c i led = 20ma i led = 10ma i led = 5ma i led = 1ma fig. 17 ?saturation voltage vs. ambient temperature v ce(sat) - saturation voltage (v) -40 -20 0 20 40 t a - ambient temperature ( c) 60 80 100 temperature - c delta vref / delta vout ( mv/v) -0.32 -0.34 -0.36 -0.38 -0.40 -0.42 -0.44 -0.46 -60 -40 -20 0 20 40 60 80 100 120 fig. 19 ?rate of change vref to vout vs. temperature 0.06 0.08 0.10 0.12 0.14 0.16 0.18 0.20 0.22 0.24 0.26 i led = 10ma i c = 2.5ma i led = 1ma i c = 0.1ma -40 -20 0 20 40 60 80 100 0 4 8 12 16 20 24 28 32 i c - collector current (ma) i led = 1ma 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 i led = 5ma i led = 10ma i led = 1ma i led = 20ma v ce = 5v v ce = 5v 25 c 0 c -40 c 100 c 70 c
4/8/04 p age 9 of 15 ? 2004 fairchild semiconductor corporation optically isolated error amplifier fod2743a fod2743b fod2743c 11 0 100 1000 fig. 20 ?voltage gain vs. frequency frequency - khz voltage gain - db -15 -10 -5 5 0 i f = 10ma r l = 500 ? i f = 10ma r l = 100 ? i f = 10ma r l = 1k ? v cc = 10v i f = 1ma r l = 2.4k ? -40 -20 0 20 40 60 80 100 ta - ambient temperature - c package power dissipation - mw 0 50 100 150 200 fig. 21 ?package power dissipation vs ambient temperature
4/8/04 p age 10 of 15 ? 2004 fairchild semiconductor corporation optically isolated error amplifier fod2743a fod2743b fod2743c the fod2743 the fod2743 is an optically isolated error ampli?er. it incor- porates three of the most common elements necessary to make an isolated power supply, a reference voltage, an error ampli?er, and an optocoupler. it is functionally equivalent to the popular ka431 shunt voltage regulator plus the cny17f-x optocoupler. po wering 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 ampli?er 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 second- ary 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 fod2743 attempts to regulate its fb pin to the reference v oltage, 2.5v. the ratio of the two resistors should thus be: 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 r top should be: compensation the compensation pin of the fod2743 provides the opportu- nity 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 systems loop. an excellent reference for this process may be found in practical design of po w er 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 con?guration the collector will be attached to a pull-up resistor and the emitter grounded. there is no base connection neces- sary. the value of the pull-up resistor, and the current limiting resis- tor feeding the led, must be carefully selected to account for v oltage 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 v oltage 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: select 20k ? to allow some margin. r top r bottom ------------------------- - v out v ref -------------- 1 = v out 2.5 r top ---------------------------- - 1040 a > 10v 5v r collector ----------------------------------- 4 0 0 a or r collector 12.5k ? ; > <
4/8/04 p age 11 of 15 ? 2004 fairchild semiconductor corporation optically isolated error amplifier fod2743a fod2743b fod2743c pa ck ag e dimensions (through hole) 0.200 (5.08) 0.140 (3.55) 0.100 (2.54) typ 0.022 (0.56) 0.016 (0.41) 0.020 (0.51) min 0.390 (9.91) 0.370 (9.40) 0.270 (6.86) 0.250 (6.35) 3 0.070 (1.78) 0.045 (1.14) 2 41 56 7 8 0.300 (7.62) typ 0.154 (3.90) 0.120 (3.05) 0.016 (0.40) 0.008 (0.20) 15 max pin 1 id. seating plane pa ck ag e dimensions (surface mount) lead coplanarity : 0.004 (0.10) max 0.270 (6.86) 0.250 (6.35) 0.390 (9.91) 0.370 (9.40) 0.022 (0.56) 0.016 (0.41) 0.100 (2.54) typ 0.020 (0.51) min 0.070 (1.78) 0.045 (1.14) 0.300 (7.62) typ 0.405 (10.30) min 0.315 (8.00) min 0.045 [1.14] 32 1 4 567 8 0.016 (0.41) 0.008 (0.20) pin 1 id. pa ck ag e dimensions (0.4"lead spacing) 0.200 (5.08) 0.140 (3.55) 0.100 (2.54) typ 0.022 (0.56) 0.016 (0.41) 0.004 (0.10) min 0.390 (9.91) 0.370 (9.40) 0.270 (6.86) 0.250 (6.35) 3 0.070 (1.78) 0.045 (1.14) 2 41 56 7 8 0.400 (10.16) typ 0.154 (3.90) 0.120 (3.05) 0.016 (0.40) 0.008 (0.20) 0 to 15 pin 1 id. seating plane 8 - pin dip 0.070 (1.78) 0.060 (1.52) 0.030 (0.76) 0.100 (2.54) 0.295 (7.49) 0.415 (10.54) note all dimensions are in inches (millimeters)
4/8/04 p age 12 of 15 ? 2004 fairchild semiconductor corporation optically isolated error amplifier fod2743a fod2743b fod2743c ordering information example: fod2743a x y marking information x pa ck a ging option t: 0.4 lead spacing s: surface mount lead bend sd: surface mount tape and reel (1000 per reel) y v: vde tested 1 2 6 4 3 5 de?itions 1f airchild logo 2d e vice number 3 vde mark (note: only appears on parts ordered with vde option C see order entry table) 4t wo digit year code, e.g., 03 5t wo digit work week ranging from 01 to 53 6 assembly package code 2743a b yy xx v
4/8/04 p age 13 of 15 ? 2004 fairchild semiconductor corporation optically isolated error amplifier fod2743a fod2743b fod2743c carrier tape speci?ations description symbol dimension in mm t ape width w 16.0 0.3 t ape thickness t 0.30 0.05 sprocket hole pitch p 0 4.0 0.1 sprocket hole diameter d 0 1.55 0.05 sprocket hole location e 1.75 0.10 po ck et location f 7.5 0.1 p 2 4.0 0.1 po ck et pitch p 12.0 0.1 po ck et dimensions a 0 10.30 0.20 b 0 10.30 0.20 k 0 4.90 0.20 cover tape width w 1 1.6 0.1 cover tape thickness d 0.1 max max. component rotation or tilt 10 min. bending radius r 30 d 0 p t 2 d 0 1 1 w user direction of feed 0 k b 0 a 0 w e d f p p
4/8/04 p age 14 of 15 ? 2004 fairchild semiconductor corporation optically isolated error amplifier fod2743a fod2743b fod2743c fig.21 recommended ir reflow profile ? peak reflow temperature 260 c (package surface temperature) ? time of temperature higher than 245 c 40 seconds or less ? number of reflows three 300 250 200 temperature ( c) 150 100 50 50 100 150 time (s) 10 s 40 s 260 245 200 250 fig. 22 recommended ir reflow profile
4/8/04 life support policy fairchilds 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. 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. p age 15 of 15 ? 2004 fairchild semiconductor corporation optically isolated error amplifier fod2743a fod2743b fod2743c

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