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4/10/03 optically isolated error amplifier p age 1 of 13 fod2712 ?2003 fairchild semiconductor corporation pa ckage dimensions functional block diagram description the fod2712 optically isolated ampli?r 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%. it is primarily intended for use as the error ampli?r/reference v oltage/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. features optocoupler, precision reference and error ampli?r 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 applications ? ow er system for workstations ? elecom central of?e supply ? elecom bricks * the compensation network must be attached between pins 6 and 7. pin definitions pin number pin name pin function description 1n c not connected 2c phototransistor collector 3e phototransistor emitter 4n c not connected 5 gnd ground 6 comp error ampli?r compensation. this pin is the output of the error ampli?r. * 7f bv oltage feedback. this pin is the inverting input to the error ampli?r 8 led anode led. this pin is the input to the light emitting diode. lead coplanarity : 0.004 (0.10) max 0.202 (5.13) 1 0.182 (4.63) 0.021 (0.53) 0.011 (0.28) 0.050 (1.27) typ 0.244 (6.19) 0.224 (5.69) 0.143 (3.63) 0.123 (3.13) 0.008 (0.20) 0.003 (0.08) 0.010 (0.25) 0.006 (0.16) sea ting plane 0.164 (4.16) 0.144 (3.66) note all dimensions are in inches (millimeters) 1 2 3 4 5 6 7 8 led fb comp gnd nc c e nc
4/10/03 p age 2 of 13 ?2003 fairchild semiconductor corporation optically isolated error amplifier fod2712 typical application v o v 1 r1 r2 2 3 8 6 7 5 pwm control f an4803 fod2712 notes 1. derate linearly from 25? at a rate of 2.42 mw/ ? 2. derate linearly from 25? at a rate of 1.42 mw/ ?. 3. derate linearly from 25? at a rate of 2.42 mw/ ?. 4. 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 = 25? unless otherwise speci?d.) p arameter symbol value units storage temperature t stg -55 to +125 ? operating temperature t opr -40 to +85 ? re?w temperature pro?e (refer to ?. 21) input voltage v led 13.2 v input dc current i led 20 ma collector-emitter voltage v ceo 30 v emitter-collector voltage v eco 7v collector current i c 50 ma input power dissipation (note 1) pd1 145 mw tr ansistor power dissipation (note 2) pd2 85 mw t otal power dissipation (note 3) pd3 145 mw
4/10/03 p age 3 of 13 ?2003 fairchild semiconductor corporation optically isolated error amplifier fod2712 1. the deviation parameters v ref(dev) and i ref(dev) are de?ed as the differences between the maximum and minimum values obtained over the rated temperature range. the average full-range temperature coef?ient of the reference input voltage, ? v ref , is de?ed as: where ? t a is the rated operating free-air temperature range of the device. 2. the dynamic impedance is de?ed 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 (v cc = 12v, t a = 25? unless otherwise speci?d.) input characteristics p arameter test conditions symbol min typ** max unit led forward voltage (i led = 10 ma, v comp = v fb )(fig.1) v f 1.5 v reference voltage (-40 to +85?) (v comp = v fb , i led = 10 ma (fig.1) v ref 1.221 1.259 v (25?) 1.228 1.240 1.252 deviation of v ref over temperature - see note 1 (t a = -40 to +85?) v ref (dev) 4 12 mv ratio of vref variation to the output of the error ampli?r (i led = 10 ma, v comp = v ref to 12 v) (fig.2) ? v ref / ? v comp -1.5 -2.7 mv/v f eedback input current (i led = 10 ma, r1 = 10 k ? ) (fig.3) i ref 0.15 0.5 ? deviation of i ref over temperature - see note 1 (t a = -40 to +85?) i ref (dev) 0.15 0.3 ? minimum drive current (v comp = v fb ) (fig.1) i led (min) 55 80 ? off-state error ampli?r current (v led = 6 v, v fb = 0) (fig.4) i (off) 0.001 0.1 ? error ampli?r output impedance - see note 2 (v comp = v fb , i led = 0.1 ma to 15 ma, f<1 khz) |z out | 0.25 ohm ? v ref ppm/? () v ref dev () /v ref t a 25? = () {} 10 6 ? t a ---------------------------------------------------------------------------------------------------- - = z out, tot = ? v ? i ------- -z out 1 r1 r2 ------- - +
4/10/03 p age 4 of 13 ?2003 fairchild semiconductor corporation optically isolated error amplifier fod2712 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 tog ether. 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. output characteristics (t a = 25? unless otherwise speci?d.) p arameter test conditions symbol min typ max unit collector dark current (v ce = 10 v) (fig. 5) i ceo 50 na collector-emitter voltage breakdown (i c = 1.0ma) bv ceo 70 v emitter-collector voltage breakdown (i e = 100 ?) bv eco 7v transfer characteristics (t a = 25? unless otherwise speci?d.) p arameter test conditions symbol min typ max unit current transfer ratio (i led = 10 ma, v comp = v fb , v ce = 5 v) (fig. 6) ctr 100 200 % collector-emitter saturation voltage (i led = 10 ma, v comp = v fb , i c = 2.5 ma) (fig. 6) v ce (sat) 0.4 v isolation characteristics (t a = 25? unless otherwise speci?d.) p arameter test conditions symbol min typ max unit input-output insulation leakage current (rh = 45%, t a = 25?, t = 5s, v i-o = 3000 vdc) (note. 1) i i-o 1.0 ? withstand insulation v oltage (rh <= 50%, t a = 25?, t = 1 min) (notes. 1) v iso 2500 vrms resistance (input to output) v i-o = 500 vdc (note. 1) r i-o 10 12 ohm switching characteristics (t a = 25? unless otherwise speci?d.) p arameter test conditions symbol min typ max unit bandwidth (fig. 7) b w 10 khz common mode transient immunity at output high (i led = 0 ma, ? v cm ? = 10 v pp rl = 2.2 k ? (fig. 8) (note. 2) ? cmh ? 1.0 kv/? common mode transient immunity at output low (i led = 10 ma, ? v cm ? = 10 v pp rl = 2.2 k ? (fig. 8) (note. 2) ? cml ? 1.0 kv/?
4/10/03 p age 5 of 13 ?2003 fairchild semiconductor corporation optically isolated error amplifier fod2712 i (led) v (led) v comp v comp i ceo v ce v ref v ce i (led) v f v ref v ref 82 3 2 3 v v v 6 7 5 i (led) i (led) i (c) i (off) i ref 8 6 2 3 2 3 2 3 v v 7 5 8 6 7 5 8 6 7 5 8 6 2 3 7 5 r1 8 6 r1 r2 7 5 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
4/10/03 p age 6 of 13 ?2003 fairchild semiconductor corporation optically isolated error amplifier fod2712 3 2 1 4 8 7 6 a b 5 3 4 2 1 6 5 7 8 v cc = +5v dc v cc = +5v dc i f = 10 ma i f = 0 ma (a) i f = 10 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
4/10/03 p age 7 of 13 ?2003 fairchild semiconductor corporation optically isolated error amplifier fod2712 typical performance curves v ref - reference voltage (v) i ref - reference current (na) fig. 10 reference voltage vs ambient temperature t a - ambient temperature ( c) t a - ambient temperature ( c) t a - ambient temperature ( c) -40 -20 0 20 40 60 80 1.230 1.236 1.242 1.248 1.254 i led = 10 ma fig. 11 reference current vs ambient temperature -40 -20 0 20 40 60 80 100 50 100 150 200 250 300 350 i led = 10 ma r 1 = 10 k ? fig. 12 off current vs ambient temperature -40 -20 0 20 40 60 80 100 i (off) - off current (na) 0.1 1 10 100 v led = 13.2 v v fb = 0 fig. 9a led current vs cathode voltage v comp - cathode voltage (v) v comp - cathode voltage (v) -1.0 -0.5 0.0 0.5 1.0 1.5 i led - supply current (ma) -15 -10 -5 0 5 10 15 t a = 25 c v comp = v fb fig. 9b led current vs cathode voltage i led - supply current ( a) -150 -120 -90 -60 -30 0 30 60 90 120 150 -1.0 -0.5 0.0 0.5 1.0 1.5 t a = 25 c v comp = v fb
4/10/03 p age 8 of 13 ?2003 fairchild semiconductor corporation optically isolated error amplifier fod2712 fig.13 led forward current vs forward voltage v f - forward voltage (v) 0.95 1.00 1.05 1.10 1.15 1.20 1.25 1.30 1.35 i led - forward current (ma) 0 5 10 15 20 70?c 0?c 0?c 25?c 25?c fig.14 dark current vs temperature t a - ambient temperature ( c) -40 -20 0 20 40 60 80 100 i ceo - dark current (na) 0.1 1 10 100 1000 fig. 15 collector current vs ambient temperature t a - ambient temperature ( c) -40 -20 0 20 40 60 80 100 i c - collector current (ma) 0 5 10 15 20 25 30 i led = 20 ma i led = 10 ma i led = 5 ma i led = 1 ma fig. 16 current transfer ratio vs led current i led - forward current (ma) 0102 0304050 (i c /i f ) - current transfer ratio (%) 0 20 40 60 80 100 120 140 160 70?c v ce = 5 v fig. 17 saturation voltage vs ambient temperature t a - ambient temperature ( c) -40 -20 0 20 40 60 80 100 v ce (sat) - saturation voltage (v) 0.10 0.12 0.14 0.16 0.18 0.20 0.22 v ce = 10v v ce = 5 v
4/10/03 p age 9 of 13 ?2003 fairchild semiconductor corporation optically isolated error amplifier fod2712 fig. 18 collector current vs collector voltage v ce - collector-emitter voltage (v) 012345678910 i c - collector current (ma) 0 5 10 15 20 25 30 35 40 45 fig. 19 delta v ref /delta v comp vs ambient temperature t a - ambient temperature ( c) -40 -20 0 20 40 60 80 100 delta v ref /delta v comp (mv/v) -2 -1 0 1 fig. 20 voltage gain vs frequency frequency khz 10 100 1000 vo lt a ge gain, a(v o /v in ) db -15 -10 -5 0 t a = 25 c i led = 20 ma i led = 10 ma i led = 5 ma i led = 1 ma r l =1 k ? 500 ? 100 ?
4/10/03 p age 10 of 13 ?2003 fairchild semiconductor corporation optically isolated error amplifier fod2712 the fod2712 the fod2712 is an optically isolated error ampli?r. it incor- porates three of the most common elements necessary to make an isolated power supply, a reference voltage, an error ampli?r, and an optocoupler. it is functionally equivalent to the popular rc431a shunt voltage regulator plus the cny17f-3 optocoupler. po wering the secondary side the led pin in the fod2712 powers the secondary side, and in particular provides the current to run the led. the actual structure of the fod2712 dictates the minimum voltage that can be applied to the led pin: the error ampli?r 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 1.24v + 1.5v = 2.74v. 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 reg- ulation, 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 fod2712 attempts to regulate its fb pin to the reference v oltage, 1.24v. the ratio of the two resistors should thus be: the absolute value of the top resistor is set by the input offset current of 0.8?. to achieve 1% accuracy, the resistance of r top should be: compensation the compensation pin of the fod2712 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 0.1? 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 ?ractical 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 fod2712. in a normal con?uration 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 volt- age feeding the collector pull-up is +10v, and the pwm ic is the fairchild ka1h0680, which has a 5v reference. if we select a 10k ? resistor for the led, the maximum current the led can see is (12v-2.74v) /10k ? = 926?. the ctr of the opto-isolator is a minimum of 100%, and so the minimum collector current of the photo-transistor when the diode is full on is also 926?. the collector resistor must thus be such that: select 10k ? to allow some margin. r top r bottom ------------------------- - v out v ref -------------- 1 = v out 1.24 r top -------------------------------- 8 0 a > 10v 5v r collector ----------------------------------- -926 a or r collector 5.4k ? ; > <
4/10/03 p age 11 of 13 ?2003 fairchild semiconductor corporation optically isolated error amplifier fod2712 ordering information example: fod2712 x y marking information x y pa ck a ging option r1: tape and reel (500 per reel) v:vde tested r2: tape and reel (2,500 per reel) 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 ?see order entry table) 4 one digit year code, e.g., ? 5t wo digit work week ranging from ?1 to ?3 6 assembly package code 2712 s yy x v
4/10/03 p age 12 of 13 ?2003 fairchild semiconductor corporation optically isolated error amplifier fod2712 carrier tape speci?ations re?w pro?e user direction of feed 3.5 0.2 8.3 0.1 0.3 max 6.4 0.2 5.2 0.2 12.0 0.3 5.5 0.05 1.75 0.10 1.5 min 8.0 0.1 2 0.05 4.0 0.1 1.5 + 0.1/-0 0.1 max ramp up = 2?0 c/sec ? peak reflow temperature: 245 c (package surface temperature) ? time of temperature higher than 183 c for 120?80 seconds ? one time soldering reflow is recommended 230 c, 10?0 s time (minute) 0 300 250 200 150 100 50 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 t emperature ( c) time above 183 c, 120?80 sec 245 c peak
4/10/03 life support policy fairchild? 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 13 of 13 ?2003 fairchild semiconductor corporation optically isolated error amplifier fod2712

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