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5 kv rms signal and power isolated rs-485 transceiver with 15 kv esd adm2682e/adm2687e rev. 0 information furnished by analog devices is believed to be accurate and reliable. however, no responsibility is assumed by analog devices for its use, nor for any infringements of patents or other rights of third parties that may result from its use. specifications subject to change without notice. no license is granted by implication or otherwise under any patent or patent rights of analog devices. trademarks and registered trademarks are the property of their respective owners. one technology way, p.o. box 9106, norwood, ma 02062-9106, u.s.a. tel: 781.329.4700 www.analog.com fax: 781.461.3113 ?2011 analog devices, inc. all rights reserved. features 5 kv rms isolated rs-485/rs-422 transceiver, configurable as half or full duplex iso power integrated isolated dc-to-dc converter 15 kv esd protection on rs-485 input/output pins complies with ansi/tia/eia-485-a-98 and iso 8482:1987(e) data rate: 16 mbps ( adm2682e ), 500 kbps ( adm2687e ) 5 v or 3.3 v operation connect up to 256 nodes on one bus open- and short-circuit, fail-safe receiver inputs high common-mode transient immunity: >25 kv/s thermal shutdown protection safety and regulatory approvals ul recognition (pending) 5000 v rms for 1 minute per ul 1577 csa component acceptance notice #5a (pending) iec 60601-1: 400 v rms (basic), 250 v rms (reinforced) iec 60950-1: 600 v rms (basic), 380 v rms (reinforced) vde certificates of conformity (pending) din en 60747-5-2 (vde 0884 part 2): 2003-01 v iorm = 846 v peak operating temperature range: ?40c to +85c 16-lead wide-body soic with >8 mm creepage and clearance applications isolated rs-485/rs-422 interfaces industrial field networks multipoint data transmission systems functional block diagram 09927-001 adm2682e/adm2687e txd a b y z de v cc rxd re gnd 1 gnd 2 decode d r decode encode oscillator rectifier regulator v isoout iso power dc-to-dc converter v isoin digital isolation i coupler encode encode decode transceiver isolation barrier figure 1. general description the adm2682e / adm2687e are fully integrated 5 kv rms signal and power isolated data transceivers with 15 kv esd protection and are suitable for high speed communication on multipoint transmission lines. the adm2682e / adm2687e include an integrated 5 kv rms isolated dc-to-dc power supply that eliminates the need for an external dc-to-dc isolation block. they are designed for balanced transmission lines and comply with ansi/tia/eia-485-a-98 and iso 8482:1987(e). the devices integrate analog devices, inc., i coupler? technology to combine a 3-channel isolator, a three-state differential line driver, a differential input receiver, and analog devices iso power? dc-to-dc converter into a single package. the devices are powered by a single 5 v or 3.3 v supply, realizing a fully integrated signal and power isolated rs-485 solution. the adm2682e / adm2687e drivers have an active high enable. an active low receiver enable is also provided, which causes the receiver output to enter a high impedance state when disabled. the devices have current limiting and thermal shutdown features to protect against output short circuits and situations where bus contention may cause excessive power dissipation. the parts are fully specified over the industrial temperature range and are available in a highly integrated, 16-lead, wide- body soic package with >8 mm creepage and clearance. the adm2682e / adm2687e contain iso power technology that uses high frequency switching elements to transfer power through the transformer. special care must be taken during printed circuit board (pcb) layout to meet emissions standards. refer to an-0971 application note , recommendations for control of radiated emissions with isopower devices , for details on board layout considerations.
adm2682e/adm2687e rev. 0 | page 2 of 24 table of contents features .............................................................................................. 1 ? applications....................................................................................... 1 ? functional block diagram .............................................................. 1 ? general description ......................................................................... 1 ? revision history ............................................................................... 2 ? specifications..................................................................................... 3 ? adm2682e timing specifications ............................................ 4 ? adm2687e timing specifications ............................................ 4 ? package characteristics ............................................................... 4 ? regulatory information............................................................... 5 ? insulation and safety-related specifications............................ 5 ? vde 0884 insulation characteristics (pending)...................... 6 ? absolute maximum ratings............................................................ 7 ? esd caution.................................................................................. 7 ? pin configuration and function descriptions............................. 8 ? typical performance characteristics ............................................. 9 ? test circuits..................................................................................... 14 ? switching characteristics .............................................................. 15 ? circuit description......................................................................... 16 ? signal isolation ........................................................................... 16 ? power isolation ........................................................................... 16 ? truth tables................................................................................. 16 ? thermal shutdown .................................................................... 16 ? open- and short-circuit, fail-safe receiver inputs.............. 16 ? dc correctness and magnetic field immunity........................... 16 ? applications information .............................................................. 18 ? pcb layout ................................................................................. 18 ? emi considerations................................................................... 18 ? insulation lifetime ..................................................................... 19 ? isolated supply considerations ................................................ 19 ? typical applications................................................................... 20 ? outline dimensions ....................................................................... 22 ? ordering guide .......................................................................... 22 ? revision history 7/11revision 0: initial version
adm2682e/adm2687e rev. 0 | page 3 of 24 specifications all voltages are relative to their respective ground; 3.0 v cc 5.5 v. all minimum/maximum specifications apply over the entire recommended operation range, unless otherwise noted. all typical specifications are at t a = 25c, v cc = 5 v unless otherwise noted. table 1. parameter symbol min typ max unit test conditions/comments adm2687e supply current i cc data rate 500 kbps 90 ma v cc = 3.3 v, 100 load between y and z 72 ma v cc = 5 v, 100 load between y and z 125 ma v cc = 3.3 v, 54 load between y and z 98 ma v cc = 5 v, 54 load between y and z 140 ma 120 load between y and z adm2682e supply current i cc data rate = 16 mbps 175 ma 120 load between y and z 260 ma 54 load between y and z data rate = 16 mbps, 4.5 v cc 5.5 v 130 ma 120 load between y and z 200 ma 54 load between y and z isolated supply voltage v isoout 3.3 v driver differential outputs differential output voltage, loaded |v od2 | 2.0 3.6 v r l = 100 (rs-422), see figure 29 1.5 3.6 v r l = 54 (rs-485), see figure 29 |v od3 | 1.5 3.6 v ?7 v v test1 12 v, see figure 30 |v od | for complementary output states |v od | 0.2 v r l = 54 or 100 , see figure 29 common-mode output voltage v oc 3.0 v r l = 54 or 100 , see figure 29 |v oc | for complementary output states |v oc | 0.2 v r l = 54 or 100 , see figure 29 short-circuit output current i os 200 ma output leakage current (y, z) i o 30 a de = 0 v, re = 0 v, v cc = 0 v or 3.6 v, v in = 12 v ?30 a de = 0 v, re = 0 v, v cc = 0 v or 3.6 v, v in = ?7 v logic inputs de, re , txd input threshold low v il 0.27 v cc v de, re , txd input threshold high v ih 0.7 v cc v de, re , txd input current i i ?10 0.01 10 a de, re , txd receiver differential inputs differential input threshold voltage v th ?200 ?125 ?30 mv ?7 v < v cm < +12 v input voltage hysteresis v hys 15 mv v oc = 0 v input current (a, b) i i 125 a de = 0 v, v cc = 0 v or 3.6 v, v in = 12 v ?100 a de = 0 v, v cc = 0 v or 3.6 v, v in = ?7 v line input resistance r in 96 k ?7 v < v cm < +12 v logic outputs output voltage low v ol 0.2 0.4 v i o = 1.5 ma, v a ? v b = ?0.2 v output voltage high v oh v cc ? 0.3 v cc ? 0.2 v i o = ?1.5 ma, v a ? v b = 0.2 v short-circuit current 100 ma common-mode transient immunity 1 25 kv/s v cm = 1 kv, transient magnitude = 800 v 1 cm is the maximum common-mode voltage slew rate that can be sustained while maint aining specification-compliant operation. v cm is the common-mode potential difference between the logic and bus sides. the transient magnitude is the range over which the common-mode is slewed. the comm on-mode voltage slew rates apply to both rising and falling common-mode voltage edges.
adm2682e/adm2687e rev. 0 | page 4 of 24 adm2682e timing specifications t a = ?40c to +85c. table 2. parameter symbol min typ max unit test conditions/comments driver maximum data rate 16 mbps propagation delay, low to high t dplh 63 100 ns r l = 54 , c l1 = c l2 = 100 pf, see figure 31 and figure 35 propagation delay, high to low t dphl 64 100 ns r l = 54 , c l1 = c l2 = 100 pf, see figure 31 and figure 35 output skew t skew 1 8 ns r l = 54 , c l1 = c l2 = 100 pf, see figure 31 and figure 35 rise time/fall time t dr , t df 15 ns r l = 54 , c l1 = c l2 = 100 pf, see figure 31 and figure 35 enable time t zl , t zh 120 ns r l = 110 , c l = 50 pf, see figure 32 and figure 37 disable time t lz , t hz 150 ns r l = 110 , c l = 50 pf, see figure 32 and figure 37 receiver propagation delay, low to high t rplh 94 110 ns c l = 15 pf, see figure 33 and figure 36 propagation delay, high to low t rphl 95 110 ns c l = 15 pf, see figure 33 and figure 36 output skew 1 t skew 1 12 ns c l = 15 pf, see figure 33 and figure 36 enable time t zl , t zh 15 ns r l = 1 k, c l = 15 pf, see figure 34 and figure 38 disable time t lz , t hz 15 ns r l = 1 k, c l = 15 pf, see figure 34 and figure 38 1 guaranteed by design. adm2687e timing specifications t a = ?40c to +85c. table 3. parameter symbol min typ max unit test conditions/comments driver maximum data rate 500 kbps propagation delay, low to high t dplh 250 503 700 ns r l = 54 , c l1 = c l2 = 100 pf, see figure 31 and figure 35 propagation delay, high to low t dphl 250 510 700 ns r l = 54 , c l1 = c l2 = 100 pf, see figure 31 and figure 35 output skew t skew 7 100 ns r l = 54 , c l1 = c l2 = 100 pf, see figure 31 and figure 35 rise time/fall time t dr , t df 200 1100 ns r l = 54 , c l1 = c l2 = 100 pf, see figure 31 and figure 35 enable time t zl , t zh 2.5 s r l = 110 , c l = 50 pf, see figure 32 and figure 37 disable time t lz , t hz 200 ns r l = 110 , c l = 50 pf, see figure 32 and figure 37 receiver propagation delay, low to high t rplh 91 200 ns c l = 15 pf, see figure 33 and figure 36 propagation delay, high to low t rphl 95 200 ns c l = 15 pf, see figure 33 and figure 36 output skew t skew 4 30 ns c l = 15 pf, see figure 33 and figure 36 enable time t zl , t zh 15 ns r l = 1 k, c l = 15 pf, see figure 34 and figure 38 disable time t lz , t hz 15 ns r l = 1 k, c l = 15 pf, see figure 34 and figure 38 package characteristics table 4. parameter symbol min typ max unit test conditions/comments resistance (input-to-output) 1 r i-o 10 12 capacitance (input-to-output) 1 c i-o 3 pf f = 1 mhz input capacitance 2 c i 4 pf 1 device considered a 2-terminal device: short together pin 1 to pin 8 and short together pin 9 to pin 16. 2 input capacitance is from any input data pin to ground.
adm2682e/adm2687e rev. 0 | page 5 of 24 regulatory information table 5. adm2682e/adm2687e approvals (pending) organization approval type ul (pending) to be recognized under the ul 1577 component recognition program of underwriters laboratories, inc. single protection, 5000 v rms isolation voltage. in accordance with ul 1577, each adm2682e / adm2687e is proof tested by applying an insulation test voltage 6000 v rms for 1 second. csa (pending) to be approved under csa component acceptance notice #5a. reinforced insulation per iec 60601-1, 250 v rms (353 v peak) maximum working voltage. basic insulation per iec 60601-1, 400 v rms (566 v peak) maximum working voltage. reinforced insulation per csa 60950-1-07 and iec 60950-1, 380 v rms (537 v peak) maximum working voltage. basic insulation per csa 60950-1-07 and iec 60950-1, 600 v rms (848 v peak) maximum working voltage. vde (pending) to be certified according to din en 60747-5-2 (vde 0884 part 2):2003-01. in accordance with din en 60747-5-2, each adm2682e / adm2687e is proof tested by applying an insulation test voltage 1590 v peak for 1 second. insulation and safety-related specifications table 6. parameter symbol value unit test conditions/comments rated dielectric insulation voltage 5000 v rms 1-minute duration minimum external air gap (clearance) l(i01) >8.0 mm measured from input terminals to output terminals, shortest distance through air minimum external tracking (creepage) l(i02) >8.0 mm measured from input terminals to output terminals, shortest distance along body minimum internal gap (internal clearance) 0.017 min mm insulation distance through insulation tracking resistance (comparative tracking index) cti >175 v din iec 112/vde 0303-1 isolation group iiia material group (din vde 0110:1989-01, table 1)
adm2682e/adm2687e rev. 0 | page 6 of 24 vde 0884 insulation characteristics (pending) this isolator is suitable for basic electrical isolation only within the safety limit data. maintenance of the safety data must be ensured by means of protective circuits. table 7. description test conditions/comments symbol characteristic unit classifications installation classification per din vde 0110 for rated mains voltage 300 v rms i to iv 450 v rms i to iii 600 v rms i to ii climatic classification 40/85/21 pollution degree table 1 of din vde 0110 2 voltage maximum working insulation voltage v iorm 846 v peak input-to-output test voltage v pr method b1 v iorm 1.875 = v pr , 100% production tested, t m = 1 sec, partial discharge < 5 pc 1590 v peak method a after environmental tests, subgroup 1 v iorm 1.6 = v pr , t m = 60 sec, partial discharge < 5 pc 1375 v peak after input and/or safety test, subgroup 2/subgroup 3 v iorm 1.2 = v pr , t m = 60 sec, partial discharge < 5 pc 1018 v peak highest allowable overvoltage transient overvoltage, t tr = 10 sec v tr 6000 v peak safety-limiting values maximum value allowed in the event of a failure case temperature t s 150 c input current i s, input 265 ma output current i s, output 335 ma insulation resistance at t s v io = 500 v r s >10 9
adm2682e/adm2687e rev. 0 | page 7 of 24 absolute maximum ratings t a = 25c, unless otherwise noted. all voltages are relative to their respective ground. table 9. maximum continuous working voltage 1 parameter max unit reference standard ac voltage bipolar waveform 424 v peak all certifications, 50-year minimum lifetime unipolar waveform basic insulation 600 v peak reinforced insulation 537 v peak maximum approved working voltage per iec 60950-1 dc voltage basic insulation 600 v peak reinforced insulation 537 v peak maximum approved working voltage per iec 60950-1 table 8. parameter rating v cc ?0.5 v to +7 v digital input voltage (de, re , txd) ?0.5 v to v dd + 0.5 v digital output voltage (rxd) ?0.5 v to v dd + 0.5 v driver output/receiver input voltage ?9 v to +14 v operating temperature range ?40c to +85c storage temperature range ?55c to +150c esd (human body model) on a, b, y, and z pins 15 kv esd (human body model) on other pins 2 kv thermal resistance ja 52c/w lead temperature soldering (10 sec) 260c vapor phase (60 sec) 215c infrared (15 sec) 220c 1 refers to continuous voltage magni tude imposed across the isolation barrier. see the insulation lifetime section for more details. esd caution stresses above those listed under absolute maximum ratings may cause permanent damage to the device. this is a stress rating only; functional operation of the device at these or any other conditions above those indicated in the operational section of this specification is not implied. exposure to absolute maximum rating conditions for extended periods may affect device reliability.
adm2682e/adm2687e rev. 0 | page 8 of 24 pin configuration and fu nction descriptions gnd 1 1 v cc 2 rxd 3 re 4 gnd 2 16 v isoin 15 a 14 b 13 de 5 z 12 txd 6 y 11 v cc 7 v isoout 10 gnd 1 8 gnd 2 9 notes 1. pin 10 and pin 15 must be connected externally. 09927-002 adm2682e/ adm2687e top view (not to scale) figure 2. pin configuration table 10. pin function descriptions pin no. mnemonic description 1 gnd 1 ground, logic side. 2 v cc logic side power supply. it is recommended that a 0.1 f and a 0.01 f decoupling capacitor be fitted between pin 2 and pin 1. 3 rxd receiver output data. this output is hi gh when (a ? b) ?30 mv and low when (a ? b) C200 mv. the output is tristated when the receiver is disabled, that is, when re is driven high. 4 re receiver enable input. this is an active-low input. driv ing this input low enables the receiver, while driving it high disables the receiver. 5 de driver enable input. driving th is input high enables the driver, whil e driving it low disables the driver. 6 txd driver input. data to be transmitted by the driver is appl ied to this input. 7 v cc logic side power supply. it is recommended that a 0.1 f and a 10 f decoupling capacitor be fitted between pin 7 and pin 8. 8 gnd 1 ground, logic side. 9 gnd 2 ground, bus side. 10 v isoout isolated power supply output. this pin must be connected externally to v isoin . it is recommended that a reservoir capacitor of 10 f and a decoupling capacitor of 0.1 f be fitted between pin 10 and pin 9. 11 y driver noninverting output 12 z driver inverting output 13 b receiver inverting input. 14 a receiver noninverting input. 15 v isoin isolated power supply input. this pi n must be connected externally to v isoout . it is recommended that a 0.1 f and a 0.01 f decoupling capacitor be fitted between pin 15 and pin 16. 16 gnd 2 ground, bus side.
adm2682e/adm2687e rev. 0 | page 9 of 24 typical performance characteristics 200 0 20 40 60 80 100 120 140 160 180 ?40 ?15 10 35 60 85 temperature (c) supply current, i cc (ma) no load r l = 54 ? r l = 120 ? 09927-203 figure 3. adm2682e supply current (i cc ) vs. temperature (data rate = 16 mbps, de = 3.3 v, v cc = 3.3 v) 160 0 20 40 60 80 100 120 140 ?40 ?15 10 35 60 85 temperature (c) supply current, i cc (ma) no load r l = 54 ? r l = 120 ? 09927-204 figure 4. adm2682e supply current (i cc ) vs. temperature (data rate = 16 mbps, de = 5 v, v cc = 5 v) 180 160 0 20 40 60 80 100 120 140 1 4 7 10 13 16 data rate (mbps) supply current, i cc (ma) no load r l = 54 ? r l = 120 ? 09927-205 figure 5. adm2682e supply current (i cc ) vs. data rate (t a = 25c, de = 3.3 v, v cc = 3.3 v) 140 0 20 40 60 80 100 120 1 4 7 10 13 16 data rate (mbps) supply current, i cc (ma) no load r l = 54 ? r l = 120 ? 09927-206 figure 6. adm2682e supply current (i cc ) vs. data rate (t a = 25c, de = 5 v, v cc = 5 v) 120 0 20 40 60 80 100 ?40 ?15 10 35 60 85 temperature (c) supply current, i cc (ma) no load r l = 54 ? r l = 120 ? 09927-207 figure 7. adm2687e supply current (i cc ) vs. temperature (data rate = 500 kbps, de = 5 v, v cc = 5 v) 160 0 20 40 60 80 100 120 140 ?40 ?15 10 35 60 85 temperature (c) supply current, i cc (ma) no load r l = 54 ? r l = 120 ? 09927-208 figure 8. adm2687e supply current (i cc ) vs. temperature (data rate = 500 kbps, de = 3.3 v, v cc = 3.3 v)
adm2682e/adm2687e rev. 0 | page 10 of 24 140 120 100 80 60 40 20 0 50 200 125 275 350 425 500 data rate (kbps) supply current, i cc (ma) no load r l = 54 ? r l = 120 ? 09927-209 figure 9. adm2687e supply current (i cc ) vs. data rate (t a = 25c, de = 3.3 v, v cc = 3.3 v) 120 100 80 60 40 20 0 50 200 125 275 350 425 500 data rate (kbps) supply current, i cc (ma) no load r l = 54 ? r l = 120 ? 09927-210 figure 10. adm2687e supply current (i cc ) vs. data rate (t a = 25c, de = 5 v, v cc = 5 v) 50 52 54 56 58 60 62 64 66 68 70 72 driver propagation delay (ns) temperature (c) t dphl t dplh ?40 ?15 10 35 60 85 09927-107 figure 11. adm2682e differential driver propagation delay vs. temperature 400 420 440 460 480 500 520 540 560 580 600 driver propagation delay (ns) temperature (c) t dphl t dplh ?40 ?15 10 35 60 85 09927-108 figure 12. adm2687e differential driver propagation delay vs. temperature ch1 2.0v ch3 2.0v ch2 2.0v txd z y m10.00ns a ch1 1.28v 1 3 09927-109 figure 13. adm2682e driver propagation delay ch1 2.0v ch3 2.0v ch2 2.0v m200ns a ch1 2.56v 1 3 txd y z 09927-110 figure 14. adm2687e driver propagation delay
adm2682e/adm2687e rev. 0 | page 11 of 24 ?70 ?60 ?50 ?40 ?30 ?20 ?10 0 012345 output current (ma) output high voltage (v) 09927-111 figure 15. receiver output current vs. receiver output high voltage 0 10 20 30 40 50 60 012345 output current (ma) output low voltage (v) 09927-112 figure 16. receiver output current vs. receiver output low voltage 4.65 4.66 4.67 4.68 4.69 4.70 4.71 4.72 4.73 4.74 4.75 output high voltage (v) temperature (c) ?40 ?15 10 35 60 85 09927-113 figure 17. receiver output high voltage vs. temperature 0.20 0.22 0.24 0.26 0.28 0.30 0.32 output low voltage (v) temperature (c) ?40 ?15 10 35 60 85 09927-114 figure 18. receiver output low voltage vs. temperature b a rxd ch1 2.0v ch3 2.0v ch2 2.0v m10.00ns a ch1 2.56v 1 3 09927-115 figure 19. adm2682e receiver propagation delay ch1 2.0v ch3 2.0v ch2 2.0v m10.00ns a ch1 2.56v 1 3 b a rxd 09927-116 figure 20. adm2687e receiver propagation delay
adm2682e/adm2687e rev. 0 | page 12 of 24 93 92 94 95 96 97 98 ?40 ?15 10 35 60 85 receiver propa g a tion del a y (ns) temperature (c) t rphl t rplh 09927-117 figure 21. adm2682e receiver propagation delay vs. temperature 90 91 92 93 94 95 96 97 98 99 100 receiver propagation delay (ns) temperature (c) t rphl t rplh ?40 ?15 10 35 60 85 09927-118 figure 22. adm2687e receiver propagation delay vs. temperature 3.39 3.38 3.37 3.36 3.35 3.34 3.33 ?40 10 ?15 35 60 85 temperature (c) isolated supply voltage (v) no load r l = 54 ? r l = 120 ? 09927-223 figure 23. adm2682e isolated supply voltage vs. temperature (v cc = 3.3 v, data rate = 16 mbps) 3.44 3.38 3.39 3.40 3.41 3.42 3.43 3.37 3.36 3.35 3.34 ?40 10 ?15 35 60 85 temperature (c) isolated supply voltage (v) no load r l = 54 ? r l = 120 ? 09927-224 figure 24. adm2682e isolated supply voltage vs. temperature (v cc = 5 v, data rate = 16 mbps) 3.37 3.34 3.35 3.36 3.33 3.32 3.31 3.30 ?40 10 ?15 35 60 85 temperature (c) isolated supply voltage (v) no load r l = 54 ? r l = 120 ? 09927-225 figure 25. adm2687e isolated supply voltage vs. temperature (v cc = 3.3 v, data rate = 500 kbps) 3.39 3.38 3.35 3.36 3.37 3.34 3.33 3.32 3.31 ?40 10 ?15 35 60 85 temperature (c) isolated supply voltage (v) no load r l = 54 ? r l = 120 ? 09927-226 figure 26. adm2687e isolated supply voltage vs. temperature (v cc = 5 v, data rate = 500 kbps
adm2682e/adm2687e rev. 0 | page 13 of 24 60 0 10 20 30 40 50 ?40 ?15 10 35 60 85 temperature (c) isolated supply current (ma) no load r l = 54 ? r l = 120 ? 09927-227 40 0 5 10 15 20 30 35 25 ?40 ?15 10 35 60 85 temperature (c) isolated supply current (ma) no load r l = 54 ? r l = 120 ? 09927-228 figure 27. adm2682e isolated supply current vs. temperature (v cc = 3.3 v, data rate = 16 mbps) figure 28. adm2687e isolated supply current vs. temperature (v cc = 3.3 v, data rate = 500 kbps)
adm2682e/adm2687e rev. 0 | page 14 of 24 test circuits y z t xd v od2 v oc r l r l 2 2 09927-003 figure 29. driver voltage measurement y z t xd v od3 v test 375 ? 60 ? 375 ? 09927-004 figure 30. driver voltage measurement over common mode y z t xd c l c l r l 09927-005 figure 31. driver propagation delay y z t xd de s1 s2 v cc r l 110 ? v out c l 50pf 09927-006 figure 32. driver enable/disable c l v out re a b 09927-007 rxd figure 33. receiver propagation delay c l r l v out v cc re s1 s2 +1.5v ? 1.5v re in 09927-008 rxd figure 34. receiver enable/disable
adm2682e/adm2687e rev. 0 | page 15 of 24 switching characteristics z y t dplh t dr t dphl t df 1/2v o v o 90% point 10% point 90% point 10% point v diff = v (y) ? v (z) ?v o v diff t skew = t dphl ?t dplh +v o 0v v cc v cc /2 v cc /2 09927-009 figure 35. driver propagation delay, rise/fall timing a ? b rxd 0v 1.5v 1.5v v ol v oh t rplh 0v t rphl t skew = | t rplh ? t rphl | 09927-010 figure 36. receiver propagation delay de y , z y , z v cc 0v v ol v oh 0.5v cc 0.5v cc t zl t zh t lz t hz v oh ? 0.5v v ol + 0.5v 2.3v 2.3v 09927-011 figure 37. driver enable/disable timing output low output high 1.5v 1.5v rxd rxd re 0v v ih v il t zl t zh t lz t hz v oh ? 0.5v v ol + 0.5v v ol v oh 0.5v cc 0.5v cc 09927-012 figure 38. receiver enable/disable timing
adm2682e/adm2687e rev. 0 | page 16 of 24 circuit description signal isolation the adm2682e / adm2687e signal isolation of 5 kv rms is implemented on the logic side of the interface. the part achieves signal isolation by having a digital isolation section and a trans- ceiver section (see figure 1 ). data applied to the txd and de pins and referenced to logic ground (gnd 1 ) are coupled across an isolation barrier to appear at the transceiver section referenced to isolated ground (gnd 2 ). similarly, the single-ended receiver output signal, referenced to isolated ground in the transceiver section, is coupled across the isolation barrier to appear at the rxd pin referenced to logic ground. power isolation the adm2682e / adm2687e power isolation of 5 kv rms is implemented using an iso power integrated isolated dc-to-dc converter. the dc-to-dc converter section of the adm2682e / adm2687e works on principles that are common to most modern power supplies. it is a secondary side controller architecture with isolated pulse-width modulation (pwm) feedback. v cc power is supplied to an oscillating circuit that switches current into a chip-scale air core transformer. power transferred to the secondary side is rectified and regulated to 3.3 v. the secondary (v iso ) side controller regulates the output by creating a pwm control signal that is sent to the primary (v cc ) side by a dedicated i coupler (5 kv rms signal isolated) data channel. the pwm modulates the oscillator circuit to control the power being sent to the secondary side. feedback allows for significantly higher power and efficiency. truth tables the truth tables in this section use the abbreviations found in table 11 . table 11. truth table abbreviations letter description h high level l low level x dont care i indeterminate z high impedance (off ) nc disconnected table 12. transmitting (see table 11 for abbreviations) inputs outputs de txd y z h h h l h l l h l x z z x x z z table 13. receiving (see table 11 for abbreviations) inputs output a ? b re rxd ?0.03 v l or nc h ?0.2 v l or nc l ?0.2 v < a ? b < ?0.03 v l or nc i inputs open l or nc h x h z thermal shutdown the adm2682e / adm2687e contain thermal shutdown circuitry that protects the parts from excessive power dissipation during fault conditions. shorting the driver outputs to a low impedance source can result in high driver currents. the thermal sensing circuitry detects the increase in die temperature under this condition and disables the driver outputs. this circuitry is designed to disable the driver outputs when a die temperature of 150c is reached. as the device cools, the drivers are reenabled at a temperature of 140c. open- and short-circuit, fail-safe receiver inputs the receiver inputs have open- and short-circuit, fail-safe features that ensure that the receiver output is high when the inputs are open or shorted. during line-idle conditions, when no driver on the bus is enabled, the voltage across a terminating resistance at the receiver input decays to 0 v. with traditional transceivers, receiver input thresholds specified between ?200 mv and +200 mv mean that external bias resistors are required on the a and b pins to ensure that the receiver outputs are in a known state. the short-circuit, fail-safe receiver input feature eliminates the need for bias resistors by specifying the receiver input threshold between ?30 mv and ?200 mv. the guaranteed negative threshold means that when the voltage between a and b decays to 0 v, the receiver output is guaranteed to be high. dc correctness and magnetic field immunity the digital signals transmit across the isolation barrier using i coupler technology. this technique uses chip-scale transformer windings to couple the digital signals magnetically from one side of the barrier to the other. digital inputs are encoded into waveforms that are capable of exciting the primary transformer winding. at the secondary winding, the induced waveforms are decoded into the binary value that was originally transmitted. positive and negative logic transitions at the isolator input cause narrow (~1 ns) pulses to be sent to the decoder via the transformer. the decoder is bistable and is, therefore, either set or reset by the pulses, indicating input logic transitions. in the absence of logic transitions at the input for more than 1 s, periodic sets of refresh pulses indicative of the correct input state are sent to ensure dc correctness at the output. if the decoder receives no internal pulses of more than approximately 5 s, the input side
adm2682e/adm2687e rev. 0 | page 17 of 24 is assumed to be unpowered or nonfunctional, in which case, the isolator output is forced to a default state by the watchdog timer circuit. this situation should occur in the adm2682e / adm2687e devices only during power-up and power-down operations. the limitation on the adm2682e / adm2687e magnetic field immunity is set by the condition in which induced voltage in the transformer receiving coil is sufficiently large to either falsely set or reset the decoder. the following analysis defines the conditions under which this can occur. the 3.3 v operating condition of the adm2682e / adm2687e is examined because it represents the most susceptible mode of operation. the pulses at the transformer output have an amplitude of >1.0 v. the decoder has a sensing threshold of about 0.5 v, thus establishing a 0.5 v margin in which induced voltages can be tolerated. the voltage induced across the receiving coil is given by v = (? d / dt )? r n 2 ; n = 1, 2, , n where: is magnetic flux density (gauss). n is the number of turns in the receiving coil. r n is the radius of the n th turn in the receiving coil (cm). given the geometry of the receiving coil in the adm2682e / adm2687e and an imposed requirement that the induced voltage be, at most, 50% of the 0.5 v margin at the decoder, a maximum allowable magnetic field is calculated as shown in figure 39 . magnetic field frequency (hz) 100 maximum allowable magnetic flux density (kgauss) 0.001 1m 10 0.01 1k 10k 10m 0.1 1 100m 100k 09927-019 figure 39. maximum allowable external magnetic flux density for example, at a magnetic field frequency of 1 mhz, the maximum allowable magnetic field of 0.2 kgauss induces a voltage of 0.25 v at the receiving coil. this is about 50% of the sensing threshold and does not cause a faulty output transition. similarly, if such an event occurs during a transmitted pulse (and is of the worst-case polarity), it reduces the received pulse from >1.0 v to 0.75 v, which is still well above the 0.5 v sensing threshold of the decoder. the preceding magnetic flux density values correspond to specific current magnitudes at given distances from the adm2682e / adm2687e transformers. figure 40 expresses these allowable current magnitudes as a function of frequency for selected distances. as shown in figure 40 , the adm2682e / adm2687e are extremely immune and can be affected only by extremely large currents operated at high frequency very close to the component. for the 1 mhz example, a 0.5 ka current must be placed 5 mm away from the adm2682e / adm2687e to affect component operation. magnetic field frequency (hz) maximum allowable current (ka) 1k 100 10 1 0.1 0.01 1k 10k 100m 100k 1m 10m distance = 5mm distance = 1m distance = 100mm 09927-020 figure 40. maximum allowable current for various current-to- adm2682e / adm2687e spacings note that in combinations of strong magnetic field and high frequency, any loops formed by pcb traces can induce error voltages sufficiently large to trigger the thresholds of succeeding circuitry. take care in the layout of such traces to avoid this possibility.
adm2682e/adm2687e rev. 0 | page 18 of 24 applications information pcb layout the adm2682e / adm2687e isolated rs-422/rs-485 transceiver contains an iso power integrated dc-to-dc converter, requiring no external interface circuitry for the logic interfaces. power supply bypassing is required at the input and output supply pins (see figure 41 ). the power supply section of the adm2682e / adm2687e uses an 180 mhz oscillator frequency to pass power efficiently through its chip-scale transformers. in addition, the normal operation of the data section of the i coupler introduces switching transients on the power supply pins. bypass capacitors are required for several operating frequencies. noise suppression requires a low inductance, high frequency capacitor, whereas ripple suppression and proper regulation require a large value capacitor. these capacitors are connected between pin 1 (gnd 1 ) and pin 2 (v cc ) and pin 7 (v cc ) and pin 8 (gnd 1 ) for v cc . the v isoin and v isoout capacitors are connected between pin 9 (gnd 2 ) and pin 10 (v isoout ) and pin 15 (v isoin ) and pin 16 (gnd 2 ). to suppress noise and reduce ripple, a parallel combination of at least two capacitors is required with the smaller of the two capacitors located closest to the device. the recommended capacitor values are 0.1 f and 10 f for v isoout at pin 9 and pin 10 and v cc at pin 7 and pin 8. capacitor values of 0.01 f and 0.1 f are recommended for v isoin at pin 15 and pin 16 and v cc at pin 1 and pin 2. the recommended best practice is to use a very low inductance ceramic capacitor, or its equivalent, for the smaller value capacitors. the total lead length between both ends of the capacitor and the input power supply pin should not exceed 10 mm. 09927-125 gnd 1 v cc rxd re gnd 2 v isoin a b de z txd y v cc v isoout gnd 1 gnd 2 1 2 3 16 15 14 4 13 5 12 6 11 7 10 8 9 adm2682e/ adm2687e 10n f 10n f 10f 10f 100nf 100nf 100nf 100nf figure 41. recommended pcb layout in applications involving high common-mode transients, ensure that board coupling across the isolation barrier is minimized. furthermore, design the board layout such that any coupling that does occur equally affects all pins on a given component side. failure to ensure this can cause voltage differentials between pins exceeding the absolute maximum ratings for the device, thereby leading to latch-up and/or permanent damage. the adm2682e / adm2687e dissipate approximately 675 mw of power when fully loaded. because it is not possible to apply a heat sink to an isolation device, the devices primarily depend on heat dissipation into the pcb through the gnd pins. if the devices are used at high ambient temperatures, provide a thermal path from the gnd pins to the pcb ground plane. the board layout in figure 41 shows enlarged pads for pin 1, pin 8, pin 9, and pin 16. implement multiple vias from the pad to the ground plane to reduce the temperature inside the chip significantly. the dimensions of the expanded pads are at the discretion of the designer and dependent on the available board space. emi considerations the dc-to-dc converter section of the adm2682e / adm2687e components must, of necessity, operate at very high frequency to allow efficient power transfer through the small transformers. this creates high frequency currents that can propagate in circuit board ground and power planes, causing edge and dipole radiation. grounded enclosures are recommended for applications that use these devices. if grounded enclosures are not possible, good rf design practices should be followed in the layout of the pcb. see the an-0971 application note , recommendations for control of radiated emissions with isopower devices , for more information.
adm2682e/adm2687e rev. 0 | page 19 of 24 e unipolar ac or dc voltage cases. any cross-insulation voltage insulation lifetime all insulation structures eventually break down when subjected to voltage stress over a sufficiently long period. the rate of insulation degradation is dependent on the characteristics of the voltage waveform applied across the insulation. analog devices conducts an extensive set of evaluations to determine the lifetime of the insulation structure within the adm2682e / adm2687e . accelerated life testing is performed using voltage levels higher than the rated continuous working voltage. acceleration factors for several operating conditions are determined, allowing calculation of the time to failure at the working voltage of interest. the values shown in table 9 summarize the peak voltages for 50 years of service life in several operating conditions. in many cases, the working voltage approved by agency testing is higher than the 50-year service life voltage. operation at working voltages higher than the service life voltage listed leads to premature insulation failure. the insulation lifetime of the adm2682e / adm2687e depends on the voltage waveform type imposed across the isolation barrier. the i coupler insulation structure degrades at different rates, depending on whether the waveform is bipolar ac, unipolar ac, or dc. figure 42 , figure 43 , and figure 44 illustrate these different isolation voltage waveforms. bipolar ac voltage is the most stringent environment. a 50-year operating lifetime under the bipolar ac condition determines the analog devices recommended maximum working voltage. in the case of unipolar ac or dc voltage, the stress on the insulation is significantly lower. this allows operation at higher working voltages while still achieving a 50-year service life. the working voltages listed in table 9 can be applied while maintaining the 50-year minimum lifetime, provided the voltage conforms to either waveform that does not conform to th figure 43 or figure 44 should be treated as a bipolar ac waveform, and its peak voltage should be limited to the 50-year lifetime voltage value listed in table 9 . 0v rated peak voltage 09927-021 figure 42. bipolar ac waveform 0v rat ed peak voltage 09927-023 figure 43. dc waveform 0v rated peak voltage notes 1. the voltage is shown as sinusodial for illustration purposes only. it is meant to represent any voltag e waveform varying between 0 and some limiting value. the limiting value can be positive or negative, but th e voltage cannot cross 0v. 09927-022 figure 44. unipolar ac waveform isolated su wer dc-to-dc pply considerations the typical output voltage of the integrated iso po isolated supply is 3.3 v. the isolated supply in the adm2682e / adm2687e is typically capable of supplying a current of 55 ma when the junction temperature of the device is kept below 130c. this includes the current required by the internal rs-485 circuitry, and typically, no additional current is available on v isoout for external applications.
adm2682e/adm2687e rev. 0 | page 20 of 24 typical applications an example application of the adm2682e / adm2687e for a full- duplex rs-485 node is shown in the circuit diagram of figure 45 . refer to the pcb layout section for the recommended placement of the capacitors shown in this circuit diagram. placement of the r t termination resistors depends on the location of the node and the network configuration. refer to an-960 application note , rs-485/rs-422 circuit implementation guide , for guidance on termination. figure 46 and figure 47 show typical applications of the adm2682e / adm2687e in half duplex and full duplex rs-485 network configurations. up to 256 transceivers can be connected to the rs-485 bus. to minimize reflections, terminate the line at the receiving end in its characteristic impedance and keep stub lengths off the main line as short as possible. for half-duplex operation, this means that both ends of the line must be terminated because either end can be the receiving end. adm2682e/adm2687e txd a b y z de rxd re isolation barrier transceiver gnd 1 gnd 1 gnd 2 encode encode encode decode decode decode d r oscillator rectifier regulator v isoout v cc v cc v isoin microcontroller and uart r t 3.3v/5v power supply 100nf 10f 100nf 10nf 100nf 10f 100nf 10nf digital isolation i coupler iso power dc-to-dc converter 09927-124 figure 45. example circuit diagram using the adm2682e / adm2687e
adm2682e/adm2687e rev. 0 | page 21 of 24 notes 1. r t is equal to the characteristic impedance of the cable. 2 . isolation not shown. abzy abzy a b z y a b z y r d r d r d r d adm2682e/ adm2687e adm2682e/ adm2687e adm2582e/ adm2587e rxd re de txd rxd re de txd r t r t rxd re de txd rxd re de txd adm2682e/ adm2687e maximum number of transceivers on bus = 256 09927-027 figure 46. adm2682e / adm2687e typical half duplex rs-485 network notes 1. r t is equal to the characteristic impedance of the cable. 2. isolation not shown. r d a b z y r d a b z y r d a b z y r d a b z y r t txd de rxd re adm2682e/ adm2687e adm2682e/ adm2687e adm2682e/ adm2687e slave rxd re de txd adm2682e/ adm2687e master slave slave rxd re de txd rxd re de txd r t maximum number of nodes = 256 09927-028 figure 47. adm2682e / adm2687e typical full duplex rs-485 network
adm2682e/adm2687e rev. 0 | page 22 of 24 outline dimensions controlling dimensions are in millimeters; inch dimensions (in parentheses) are rounded-off millimeter equivalents for reference only and are not appropriate for use in design. compliant to jedec standards ms-013-ac 10-12-2010-a 13.00 (0.5118) 12.60 (0.4961) 0.30 (0.0118) 0.10 (0.0039) 2.65 (0.1043) 2.35 (0.0925) 10.65 (0.4193) 10.00 (0.3937) 7.60 (0.2992) 7.40 (0.2913) 0 . 7 5 ( 0 . 0 2 9 5 ) 0 . 2 5 ( 0 . 0 0 9 8 ) 45 1.27 (0.0500) 0.40 (0.0157) coplanarity 0.10 0.33 (0.0130) 0.20 (0.0079) 0.51 (0.0201) 0.31 (0.0122) 8 0 16 9 8 1 1.27 (0.0500) bsc seating plane figure 48. 16-lead standard small outline package with increased creepage [soic_ic] wide body, (ri-16-1) dimensions shown in millimeters and (inches) ordering guide model 1 data rate (mbps) temperature range package description package option ADM2682EBRIZ 16 ?40c to +85c 16-lead soic_ic ri-16-1 ADM2682EBRIZ-rl7 16 ?40c to +85c 16-lead soic_ic ri-16-1 adm2687ebriz 0.5 ?40c to +85c 16-lead soic_ic ri-16-1 adm2687ebriz-rl7 0.5 ?40c to +85c 16-lead soic_ic ri-16-1 eval-adm2682eebz adm2682e evaluation board eval-adm2687eebz adm2687e evaluation board 1 z = rohs compliant part.
adm2682e/adm2687e rev. 0 | page 23 of 24 notes
adm2682e/adm2687e rev. 0 | page 24 of 24 notes ?2011 analog devices, inc. all rights reserved. trademarks and registered trademarks are the prop erty of their respective owners. d09927-0-7/11(0)

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