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? 1988 burr-brown corporation pds-881g printed in u.s.a. december, 1995 fpo iso212p applications l industrial process control: transducer channel isolator for thermocouples, rtds, pressure bridges, flow meters l 4ma to 20ma loop isolation l motor and scr control l ground loop elimination l analytical measurements l power plant monitoring l data acquisition/test equipment isolation l multiplexed systems with channel to channel isolation offset adjust 8 7 ?/p 3 +i/p 1 f 4 6 com 1 2 5 38 37 o/p low isolation barrier b +v out ss 1 com 2 +v cc 31 32 clock out 34 clock in 35 dc/dc converter o/p high offset adjust ? out ss 1 low cost, two-port isolated, 1500vrms isolation amplifier features l 12-bit accuracy l 2.5ma (typ) quiescent current l low profile (less than 0.5" high) l small footprint l external power capability ( 8v at 5ma) l master/slaves synchronization capability l input offset adjustment l low power (53mw) l single 10v to 15v supply operation description the iso212p signal isolation amplifier is a member of a series of low-cost isolation products from burr- brown. the low-profile sil plastic package allows pcb spacings of 0.5" to be achieved, and the small footprint results in efficient use of board space. to provide isolation, the design uses high-efficiency, miniature toroidal transformers in both the signal and power paths. an uncommitted input amplifier and an isolated external bipolar supply ensure the majority of input interfacing or conditioning needs can be met. the iso212p accepts an input voltage range of 5v for single 15v supply operation or 3.0v for single 10v supply operation. international airport industrial park ? mailing address: po box 11400, tucson, az 85734 ? street address: 6730 s. tucson bl vd., tucson, az 85706 ? tel: (520) 746-1111 ? twx: 910-952-1111 internet: http://www.burr-brown.com/ ? faxline: (800) 548-6133 (us/canada only) ? cable: bbrcorp ? telex: 066-6491 ? fa x: (520) 889-1510 ? immediate product info: (800) 548-6132
iso212p 2 specifications electrical at t a = +25 c and v cc = +15v, unless otherwise noted. iso212jp ISO212KP, jp-15 parameter conditions min typ max min typ max units isolation voltage rated continuous ac, 50hz 750 1500 vrms dc 1060 2120 vdc 100% test (ac, 50hz) partial discharge 1s : <5pc 1200 2400 vrms isolation-mode rejection (1) v iso = rated continuous 60hz ac 115 [ (9) db dc 160 [ db barrier resistance 10 10 [ w barrier capacitance 12 [ pf leakage current (8) v iso = 240vrms, 60hz 1 2 [[ m arms v iso = 240vrms, 50hz 1.6 [ m arms gain initial error 1 2 [[ % fsr (2) gain vs temperature 20 50 [[ ppm of fsr/ c nonlinearity (3) : kp v o = C5v to +5v 0.04 0.05 0.015 0.025 %fsr jp-15 0.04 0.05 %fsr input offset voltage offset voltage rti: kp 10 10/g 7.5 7.5/g mv jp-15 10 10/g mv vs temperature 30 30/g [ m v/ c vs power supply (4) v cc = 14v to 16v 1.5 [ mv/v adjustment range 20 [ mv input current bias 50 [ na offset 4 [ na input voltage range (5) g = 1 5 [ v resistance 10 12 [ w output output impedance 3 [ k w voltage range out hi to out lo 5 [ v min load = 1m w ripple voltage (6) f = 0 to 100khz 8 [ mvp-p f = 0 to 5khz 0.4 [ mvrms ouput compliance out hi or out lo 7.5 v frequency response small signal bandwidth i/p = 1vp-p, C3db 1 [ khz g = 1 full signal bandwidth i/p = 10vp-p, 200 [ hz g = 1 g = 10 (C3db) 1.8 khz isolated power outputs voltage outputs ( v ss 1 ) (7) no load 7.5 8 [[ vdc vs temperature C8 [ mv/ c vs load 90 [ mv/ma current output (7) (both loaded) 5 [ ma (one loaded) 8 [ ma power supplies rated voltage rated performance 15 [ v voltage range (5) 11.4 to 16 [[ v quiescent current no load 2.5 3.5 [[ ma temperature range specification 0 +70 [[ c operating C25 +85 [[ c notes: (1) isolation-mode rejection is the ratio of the change in output voltage to a change in isolation barrier voltage. it i s a function of frequency. (2) fsr = full scale range = 10v. (3) nonlinearity is the peak deviation of the output voltage from the best-fit straight line. it is expresse d as the ratio of deviation to fsr. (4) power supply rejection is the change in v os /supply change. (5) at v cc = +10.0v, input voltage range = 3.0v min. (6) ripple is the residual component of the barrier carrier frequency generated internally. (7) derated at v cc < +15v. (8) tested at 2400vrms, 50hz limit 16 m a. (9) asterisk ( [ ) same as iso212jp.
iso212p 3 pin configuration bottom view 31 +v cc 35 clock in 37 o/p low com 2 32 clock out 34 o/p high 38 com 1 2 f b 4 +v ss1 6 offset adjust 8 1 +i/p 3 Ci/p 5 Cv ss 1 7 offset adjust absolute maximum ratings supply voltage without damage ......................................................... 18v continuous isolation voltage across barrier: jp ......................... 750vrms kp, jp-15 ........... 1500vrms storage temperature range ............................................ C25 c to 100 c lead temperature (soldering, 10s) ................................................ +300 c amplifier output short-circuit duration ................ continuous to common output voltage hi or lo to com 2 .................................................. v cc /2 package drawing temperature product package number (1) range iso212jp 38-pin plastic sip 326 C25 c to +85 c iso212jp-15 38-pin plastic sip 326 C25 c to +85 c ISO212KP 38-pin plastic sip 326 C25 c to +85 c note: (1) for detailed drawing and dimension table, please see end of data sheet, or appendix c of burr-brown ic data book. package/ordering information electrostatic discharge sensitivity this integrated circuit can be damaged by esd. burr-brown recommends that all integrated circuits be handled with appropriate precautions. failure to observe proper handling and installation procedures can cause damage. esd damage can range from subtle performance degradation to complete device failure. precision integrated circuits may be more susceptible to damage because very small parametric changes could cause the device not to meet its published specifications. the information provided herein is believed to be reliable; however, burr-brown assumes no responsibility for inaccuracies or o missions. burr-brown assumes no responsibility for the use of this information, and all use of such information shall be entirely at the users own risk. pr ices and specifications are subject to change without notice. no patent rights or licenses to any of the circuits described herein are implied or granted to any third party. burr-brown does not authorize or warrant any burr-brown product for use in life support devices and/or systems. sine response (f = 200hz) 0 +5 time (ms) output voltage (v) 0 5 510 v in = ?v, g = 1 voltage out vs supply voltage +v cc 17 7 6 5 4 3 2 1 0 supply voltage v cc (v) voltage out (v) 16 15 14 13 12 11 10 9 8 7 6 5 4 +v out ? out (absolute) v in v out ? out +v out ? out ideal ideal v in typical performance curves at t a = +25 c, v s = 15v, unless otherwise noted.
iso212p 4 typical performance curves (cont) at t a = +25 c and v s = 15v, unless otherwise noted. sine response (f = 2khz) output voltage (mv) +500 0 ?00 0 500 1000 time (?) v = ?.5v, g = 1 in step response (f = 200hz) output voltage (v) +5 0 ? 0510 time (ms) v = ?v, g = 1 in step response (f = 2khz) 0 500 1000 time (?) output voltage (mv) +500 0 ?00 v = ?.5v, g = 1 in imr vs frequency 1k 10k 100k 1m 10m 85 80 75 70 65 60 55 50 45 40 frequency (hz) imr (db) 100m linearity vs clock-in rate 30 40 50 60 70 80 90 100 clock-in rate (khz) 100 90 80 70 60 50 40 30 20 10 0 linearity error (m%) 0 ?.5 ? ?.5 ? ?.5 30 40 50 60 70 80 90 100 gain error vs clock-in rate clock-in rate (khz) gain error (% fsr)
iso212p 5 discussion of specifications the iso212p is intended for applications where isolation and input signal conditioning are required. best signal-to- noise performance is obtained when the input amplifier gain setting is such that v out has a full scale range of 5v. the bandwidth is typically 1khz, making the device ideal for use in conjunction with sensors that monitor slowly varying processes. to power external functions or networks, 5ma at 8v typical is available at the isolated port. linearity performance the iso212p offers linearity performance compatible with 12-bit resolution systems (0.025%). note that the specifica- tion is based on a best-fit straight line. optional offset voltage adjustment in many applications, the untrimmed input offset voltage will be adequate. for situations where it is necessary to trim the offset, a potentiometer can be used. see figure 1 for details. it is important to keep the traces to the offset adjust pins as short as practical, because noise can be injected into the input op amp via this route. input protection if the iso212p is used in systems where a transducer or sensor does not derive its power from the isolated power available from the device, then some input protection must be present to prevent damage to the input op amp when the iso212p is not powered. a resistor of 5k w should be included to limit the output impedance of the signal source. where the op amp is configured for an inverting gain, then r in of the gain setting network can be used. for non- figure 1. power supply and signal connections shown for non-inverting, unity gain configuration. 0.1? 100k w offset adjust 8 7 5 6 ? out ss 1 +v out ss 1 1 2 +i/p com 1 5k w v in v out 38 37 32 o/p high o/p low com 2 34 35 clock out clock in 31 +v cc (1) + + (2) (2) ?/p f b 34 input ground plane output ground plane isolation barrier 10? 10? 10? tantalum 100? + inverting configurations, a separate resistor is required. neglecting this point may also lead to problems when powering on the iso212p. using v ss1 to power external circuitry the dc/dc converter in the iso212p runs at a switching frequency of 25khz. internal rectification and filtering is sufficient for most applications at low frequencies or with no external networks connected. the ripple on v ss1 will typically be 100mvp-p at 25khz. loading the supplies will increase the ripple unless extra filtering is added externally; a capacitor of 1 m f is normally sufficient for most applications, although in some cases 10 m f may be required. noise introduced onto v ss1 should be decoupled to prevent degraded performance. theory of operation the iso212p has no galvanic connection between the input and output. the analog input signal referenced to the input common (com 1) is multiplied by the gain of the input amplifier and accurately reproduced at the output. the output section uses a differential design so either the hi or lo pin may be referenced to the output common (com 2). this allows simple input signal inversion while maintaining the high impedance input configuration. a simplified dia- gram of the iso212p is shown in figure 2. the design consists of a dc/dc converter, an uncommitted input opera- tional amplifier, a modulator circuit and a demodulator circuit. magnetic isolation is provided by separate trans- formers in the power and signal paths. the dc/dc converter provides power and synchronization signals across the isolation barrier to operate the operational amplifier and modulator circuitry. it also has sufficient capacity to power external input signal conditioning net- notes: (1) optional voltage offset adjust compo- nents. (2) 10 m f decoupling to be used with external loads connected.
iso212p 6 works. the uncommitted operational amplifier may be con- figured for signal buffering or amplification, depending on the application. the modulator converts the input signal to an amplitude- modulated ac signal that is magnetically coupled to the demodulator by a miniature transformer providing the sig- nal-path isolation. the demodulator recovers the input sig- nal from the modulated signal using a synchronous tech- nique to minimize noise and interference. about the barrier for any isolation product, barrier integrity is of paramount importance in achieving high reliability. the iso212p uses miniature toroidal transformers designed to give maximum isolation performance when encapsulated with a high-die- lectric-strength material. the internal component layout is designed so that circuitry associated with each side of the barrier is positioned at opposite ends of the package. areas where high electric fields can exist are positioned in the center of the package. the result is that the dielectric strength of the barrier typically exceeds 3kvrms. isolation voltage ratings because a long term test is impractical in a manufacturing situation, the generally accepted practice is to perform a production test at a high voltage for some shorter time. the relationship between actual test voltage and the continuous derated maximum specification is an important one. histori- cally, burr-brown has chosen a deliberately conservative one: v test = (2 x acrms continuous rating) + 1000v for ten seconds, followed by a test at rated acrms voltage for one minute. this choice was appropriate for conditions where system transients were not well defined. recent improvements in high voltage stress testing have produced a more meaningful test for determining maximum permissible voltage ratings, and burr-brown has chosen to apply this new technology in the manufacture and testing of the iso212p. partial discharge when an insulation defect such as a void occurs within an insulation system, the defect will display localized corona or ionization during exposure to high voltage stress. this ioni- zation requires a higher applied voltage to start the discharge and a lower voltage to extinguish it once started. the higher start voltage is known as the inception voltage and the lower voltage is called the extinction voltage. just as the total insulation system has an inception voltage, so do the individ- ual voids. a voltage will build up across a void until its inception voltage is reached. at this point, the void will ionize, effectively shorting itself out. this action redistrib- utes electrical charge within the dielectric and is known as partial discharge. if the applied voltage gradient across the device continues to rise, another partial discharge cycle begins. the importance of this phenomenon is that if the discharge does not occur, the insulation system retains its integrity. if the discharge begins and is allowed to continue, the action of the ions and electrons within the defect will eventually degrade any organic insulation system in which they occur. the measurement of partial discharge is both useful in rating the devices and in providing quality control of the manufacturing process. the inception voltage of these voids tends to be constant, so that the measurement of total charge being re-distributed within the dielectric is a very good indicator of the size of the voids and their likelihood of becoming an incipient failure. figure 2. simplified diagram of isolation amplifier. + 4 f b 7 off adjust 3 ?/p 1 +i/p 8 off adjust 6 +v o/p ss 1 5 ? o/p ss 1 2 com 1 0.47? +8v ?v 0.47? rectifier modulator signal power 25khz oscillator demodulator 50khz 38 o/p high 37 o/p low 31 +v cc 34 clock out 35 clock in 32 com 2
iso212p 7 the bulk inception voltage, on the other hand, varies with the insulation system and the number of ionization defects. this directly establishes the absolute maximum voltage (transient) that can be applied across the test device before destructive partial discharge can begin. measuring the bulk extinction voltage provides a lower, more conservative, voltage from which to derive a safe continuous rating. in production, its acceptable to measure at a level somewhat below the expected inception voltage and then de-rate by a factor related to expectations about the system transients. the isolation amplifier has been exten- sively evaluated under a combination of high temperatures and high voltage to confirm its performance in this respect. the iso212p is free of partial discharges at rated voltages. partial discharge testing in production not only does this test method provide far more qualitative information about stress withstand levels than did previous stress tests, but it also provides quantitative measurements from which quality assurance and control measures can be based. tests similar to this test have been used by some manufacturers such as those of high voltage power distribu- tion equipment for some time, but they employed a simple measurement of rf noise to detect ionization. this method was not quantitative with regard to energy of the discharge and was not sensitive enough for small components such as isolation amplifiers. now, however, manufacturers of hv test equipment have developed means to measure partial discharge, and vde, the german standards group, has adopted use of this method for the testing of opto-couplers. to accommodate poorly defined transients, the part under test is exposed to a voltage that is 1.6 times the continuous rated voltage and must display < 5pc partial discharge level in a 100% production test. installation and operating instructions power supply and signal connections as with any mixed analog and digital signal component, correct decoupling and signal routing precautions must be used to optimize performance. figure 1 shows the proper power supply and signal connections. v cc should be by- passed to com 2 with a 0.1 m f ceramic capacitor as close to the device as possible. short leads will minimize lead inductance. a ground plane will also reduce noise problems. if a low impedance ground plane is not used, signal common lines, and either o/p high or o/p low pin should be tied directly to the ground at the supply and com 2 returned via a separate trace to the supply ground. to avoid gain and isolation mode (imr) errors introduced by the external circuit, connect grounds as indicated in figure 3. layout practices associated with isolation amplifi- ers are very important. in particular, the capacitance associ- ated with the barrier, and series resistance in the signal and reference leads, must be minimized. any capacitance across the barrier will increase ac leakage and, in conjunction with ground line resistance, may degrade high frequency imr. voltage gain modifications the uncommitted operational amplifier at the input can be used to provide gain, signal inversion, active filtering or current to voltage conversion. the standard design approach for any op-amp stage can be used, provided that the full scale voltage appearing on f b does not exceed 5v. if the input op-amp is overdriven, ripple at the output will result. to prevent this, the feedback resistor should have a minimum value of 10k w . also, it should be noted that the current required to drive the equivalent impedance of the feedback network is supplied by the internal dc/dc converter and must be taken into account when calculating the loading added to v ss1 . since gain inversion can be incorporated in either the input or output stage of the iso212p, it is possible to use the input amplifier in a non-inverting configuration and preserve the high impedance this configuration offers. signal inversion at the output is easily accomplished by connecting o/p high to com 2 instead of o/p low. isolated power output drive capability on the input side of the iso212p, there are two power supplies capable of delivering 5ma at 8v to power exter- nal circuitry. when using these supplies with external loads, it is recommended that additional decoupling in the form of 10 m f tantalum bead capacitors be added to improve the voltage regulation. loss of linearity will result if additional filtering is not used with an output load. again, power dissipated in the feedback loop around the input op amp must be subtracted from the available power output at v ss1. if the iso212p is to be used in multiple applications, care should be taken in the design of the power distribution figure 3. technique for connecting com 1 and com 2. v iso cc +v cc ? power supply load circuit r o/p low com 2 com 1 input common c int c ext 2 c ext 1 o/p high c and r have a direct effect. ext 2 c has minimal effect on total imr. ext 1 f b +
iso212p 8 external driver connected to clk in. see figure 5. the driver may be an external component with series 4000 cmos characteristics, or one of the iso212ps in the system can be used as the master clock for the system. see figure 6 and 7 for connections in multiple iso212p installations. charge isolation when more than one iso212p is used in synchronous mode, the charge which is returned from the timing capacitor (220pf in figure 5) on each transition of the clock becomes significant. figure 7 illustrates a method of isolating the clk out clamp diodes (figure 5) from this charge. a 22k w resistor (recommended maximum to use) together with the 39k w internal oscillator timing resistor (figure 5) forms a potential divider. the ratio of these resistors should be greater than 0.6 which ensures that the input voltage triggers the inverter connected to clk in. if using a single resistor, then account must be taken of the paralleled timing resistors. this means that the 22k w resistor must be halved to drive two iso212ps, or divided by 8 if driving 8 iso212ps to insure that the ratio of greater than 0.6 is maintained. the series resistors shown in figure 7 reduce the high frequency content of the power supply current. applications the iso212p isolation amplifier, together with a few low cost components, can isolate and accurately convert a 4-to- 20ma input to a 10v output with no external adjustment. its low height (0.43" (11mm) ) and small footprint (2.5" x 0.33" (57mm x 8mm) ) make it the solution of choice in 0.5" board spacing systems and in all applications where board area savings are critical. the iso212p operates from a single +15v supply and offers low power consumption and 12-bit accuracy. on the input side, two isolated power supplies capable of supplying 5ma at 8v are available to power external circuitry. network, especially when all iso212ps are synchronized. it is best to use a well decoupled distribution point and to take power to individual iso212ps from this point in a star arrangement as shown in figure 4. noise output noise is generated by residual components of the 25khz carrier that have not been removed from the signal. this noise may be reduced by adding an output low pass filter (see figure 8). the filter time constants should be set below the carrier frequency. the output from the iso212p is a switched capacitor and requires a high impedance load to prevent degradation of linearity. loads of less than 1m w will cause an increase in noise at the carrier frequency and will appear as ripple in the output waveform. since the output signal power is generated from the input side of the barrier, decoupling of the v ss 1 outputs will improve the signal to noise ratio. synchronization of the internal oscillator the iso212p has an internal oscillator and associated tim- ing components, which can be synchronized, incorporated into the design. this alleviates the requirement for an exter- nal high-power clock driver. the typical frequency of oscil- lation is 50khz. the internal clock will start when power is applied to the iso212p and clk in is not connected. because the frequencies of several iso212ps can be margin- ally different, beat frequencies ranging from a few hz to a few khz can exist in multiple amplifier applications. the design of the iso212p accommodates internal synchro- nous noise, but a synchronous beat frequency noise will not be strongly attenuated, especially at very low frequencies if it is introduced via the power, signal, or potential grounding paths. to overcome this problem in systems where several iso212ps are used, the design allows synchronization of each oscillator in a system to one frequency. do this by forcing the timing node on the internal oscillator with an figure 5. equivalent circuit, clock input/output. in- verters are cmos. figure 4. recommended decoupling and power dis- tribution. power in track resistance/inductance iso212p ground plane 100? 10? 0.1? 0.1? 0.1? 0.1? 10? 10? iso212p iso212p clamp diodes clock in +v cc com 2 220pf 39k w clock out
iso212p 9 figure 6. oscillator connections for synchronous opera- tion in multiple iso212p installations. applications flexibility in figure 8, the iso212ps +v ss 1 isolated supply powers a ref200 to provide an accurate 100 m a current source. this current is opposed by an equal but opposite current through the 75k w feedback resistor to establish an offset of C7.5v at i in = 0ma. with i in = 4-to-20ma, the output is C5 to +5v. the ratio of the 75k w and 3.12k w resistors assures the correct gain. the polarity of the output can be reversed by simply revers- ing the o/p hi and o/p lo pins. this could be used in the figure 8 circuit to change the C5v to +5v output to a +5v to C5v output range. the primary function of the output circuitry is to add gain to produce a 10v output and to reduce output impedance. the addition of a few resistors and capacitors provides a low pass filter with a cut-off frequency equal to the full signal bandwidth of the iso212p, typically 200hz. the filter response is flat to 1db and rolls off from cut off at C12db per octave. the accuracy of the ref200 and external resistors elimi- nates the need for expensive trim pots and adjustments. the errors introduced by the external circuitry only add about 10% of the iso212ps specified gain and offset voltage error. figure 8. isolated 4-20ma current receiver with output filter. figure 7. isolating the clk out node. 2 6 10? 0.1? 0.1? 0.1? 22k w 22k w 4-20ma 8 1 3.12k w 75k w 25 w +v ss 1 iso212p + 31 32 38 (o/p high) 37 (o/p low) 100k w 100k w (5%) (5%) 6.8nf (10%) 6.8nf (10%) +15v 6 ?5v 4ma to 20ma ?0v to +10v +15v +v ss 1 4 1 3 4ma to 20ma ?v to +5v + opa27 ref 200 0.02? 3 2 note: all resistors are 0.1% unless otherwise stated. 100? 0v +15v sync +v clk out clk in com 2 cc iso212p/slave +v clk out clk in com 2 cc iso212p/slave +v clk out clk in com 2 cc iso212p/master clk out clk in clk in clk in clk in slave r s 22k w 22k w 22k w 22k w 22k w slave slave slave slave master clk out clk in clk in clk in clk in slave n slave 4 slave 3 slave 2 slave 1 master
iso212p 10 note: (1) e.g., strain gauge, pressure trans- ducer, rtd, gas detection and analysis. figure 9. instrument bridge isolation amplifier. figure 10. photodiode isolation amplifier. figure 11. thermocouple amplifier with ground loop elimination, cold junction compensation and down-scale burn-out. 10? +v iso ? iso 2 6 5 + v out 37 38 31 0.1? +15v 3 4 100k 100k w w 250k w opa128j ? iso +v iso 32 10? 1 iso212p 0.1? siemens bpw21 10? +v iso ? iso 2 6 5 + v out 37 38 31 0.1? +15v 3 ref03 1k w opa1013 ?.5v +2.5v +v iso ? iso +v iso 32 10? 1 1k w 1k w (1) 1k w iso212p 4 100 w 99k w opa1013 ? iso v out +15v 1 ? iso 4 iso212jp 8k w 4k w 1m w 100 w t.c. 3 opa177 +v iso ? iso 99k w 1k w
iso212p 11 figure 12. isolated current monitoring applications. figure 13. isolated temperature sensing and amplification. 10? +v ss1 ? ss1 2 6 5 + 1 to 5v 37 38 31 0.1? +15v 3 4 32 10? 1 iso212p ref200 150 +v ss1 ? ss1 2 6 1 5 3 4 87 100? 7.87k w 200? pt100 ?00? to 850? w 200k w + 37 38 31 0.1? +15v 90k 10k w w 32 120vrms 100a 4.7v 4.7v 200k w 0.1? 3-phase y-connected power transformer + 100k 1k w w +500vdc 100k w 100k w 6.8nf +15v ?5v 6.8nf 22k w 22k w 3 2 6 opa27 ?0v to +10v iso212p dc motor v = 50mv (fs) d v d 1 3 4 2 1 3 4 2 or

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