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15 kv esd-protected, 3.3 v,12 mbps, eia rs-485/rs-422 transceiver adm3485e rev. d 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 ?2000-2010 analog devices, inc. all rights reserved. features tia/eia rs-485/rs-422 compliant 15 kv esd protection on rs-485 input/output pins 12 mbps data rate half-duplex transceiver up to 32 nodes on the bus receiver open-circuit, fail-safe design low power shutdown current outputs high-z when disabled or powered off common-mode input range: ?7 v to +12 v thermal shutdown and short-circuit protection industry-standard 75176 pinout 8-lead narrow soic package applications power/energy metering telecommunications emi-sensitive systems industrial control local area networks functional block diagram adm3485e ro re de di b a r d 03338-001 figure 1. general description the adm3485e is a 3.3 v, low power data transceiver with 15 kv esd protection, suitable for half-duplex communi- cation on multipoint bus transmission lines. the adm3485e is designed for balanced data transmission and complies with tia/eia standards rs-485 and rs-422. the adm3485e is a half-duplex transceiver that shares differential lines and has separate enable inputs for the driver and the receiver. the devices have a 12 k receiver input impedance, which allows up to 32 transceivers on a bus. because only one driver should be enabled at any time, the output of a disabled or powered-down driver is tristated to avoid overloading the bus. the receiver has a fail-safe feature that ensures a logic high output when the inputs are floating. excessive power dissipation caused by bus contention or by output shorting is prevented with a thermal shutdown circuit. the part is fully specified over the industrial temperature range and is available in an 8-lead narrow soic package.
adm3485e rev. d | page 2 of 16 table of contents features .............................................................................................. 1 applications ....................................................................................... 1 functional block diagram .............................................................. 1 general description ......................................................................... 1 revision history ............................................................................... 2 specifications ..................................................................................... 3 timing specifications ....................................................................... 4 absolute maximum ratings ............................................................ 5 thermal resistance ...................................................................... 5 esd caution .................................................................................. 5 pin configuration and pin function de scriptions ...................... 6 test circuits and switching characteristics ...................................7 typical performance characteristics ..............................................9 standards and testing .................................................................... 11 esd testing ................................................................................. 11 applications information .............................................................. 12 differential data transmission ................................................ 12 cable and data rate ................................................................... 12 receiver open - circuit fail - safe ............................................... 12 outline dimensions ....................................................................... 13 ordering guide .......................................................................... 13 revision history 8/10 rev. c to rev. d changes to tab le 1, driver , logic inputs ...................................... 3 12/06 rev. b to rev. c updated format .................................................................. universal removed pdip model ....................................................... universal changes to features , applications, and general description .... 1 changes to specifications ................................................................ 3 changes to timing specifications .................................................. 4 changes to absolute maximu m ratings ....................................... 5 reorganized test circuits and switching characteristics section ..................................................................... 7 replaced figure 3 to figure 11 ....................................................... 7 deleted figure 12 to figure 14 ........................................................ 8 changes to figure 15 to figure 20 .................................................. 9 changes to figure 21 and figure 22 ............................................. 10 changes to table 9 .......................................................................... 11 deleted figure 2 4 ............................................................................ 11 removed fast transient burst immunity (iec1000 -4- 4) section ................................................................... 12 updated outline dimensions ....................................................... 13 changes to ordering guide .......................................................... 13 10/04 rev. a to rev. b updated format .................................................................. universal changes to power - supply current, table 1 .................................. 3 updated outline dimensions ....................................................... 14 changes to ordering guide .......................................................... 14 5/00 rev. 0 to rev. a
adm3485e rev. d | page 3 of 16 specifications v cc = +3.3 v 0.3 v. all specifications t min to t max , unless otherwise noted. table 1. parameter symbol min typ max unit test conditions/comments driver differenti al outputs differential output voltage v od 2.0 v r l = 10 0 ? (rs - 422) (see figure 3 ) 1.5 v r l = 54 ? (rs - 485) (see figure 3 ) 1.5 v r l = 60 ? (rs - 485) (see figure 4 ) ?|v od | for complementary output states 1 ?v od 0.2 v r l = 5 4 ? or 100 ? (see figure 3 ) common - mode output voltage v oc 3 v r l = 54 ? or 100 ? ( see figure 3 ) ?|v oc | for complementary output states 1 ?v oc 0.2 v r l = 54 ? or 100 ? (see figure 3 ) short - circuit output current i osd C250 ma v out = C7 v 250 ma v out = 12 v logic inputs input low voltage v il 0.8 v de, di, re input high voltage v ih 2.0 v de, di, re logic input current i in1 2 a de, di, re receiver differential inputs differential input threshold voltage v th C0.2 +0.2 v C 7 v < v cm < +12 v input voltage hysteresis ?v th 50 mv v cm = 0 v input resistance (a, b) r in 12 k? C 7 v < v cm < +12 v input current (a, b) i in2 1.0 ma de = 0 v, v cc = 0 v or 3.6 v, v in = 12 v C0.8 ma de = 0 v, v cc = 0 v or 3.6 v, v in = C 7 v ro logic output output voltage high v oh v cc C 0.4 v v i out = C 1.5 ma, v id = 200 mv (see figure 5 ) output voltage low v ol 0.4 v i out = 2.5 ma, v id = 200 mv (see figure 5 ) short - circuit output current i osr 8 60 ma 0 v < v ro < v cc tristate output leakage current i ozr 1 a v cc = 3.6 v, 0 v < v out < v cc power supply current voltage range v cc 3.0 3.6 v supply current i cc 1.1 2.2 ma no load, di = 0 v or v cc , de = v cc , re = 0 v or v cc 0.95 1.9 ma no load, di = 0 v or v cc , de = 0 v, re = 0 v shutdown current i shdn 0.002 1 a de = 0 v, re = v cc , di = 0 v or v cc esd protection a, b pins 15 kv human body model all pins except a, b 4 kv human body model 1 |v od | and |v oc | are the changes in v od and v oc , respectively, when di input changes state.
adm3485e rev. d | page 4 of 16 timing specification s v cc = 3.3 v, t a = 25c. table 2. parameter symbol min typ max unit test conditions/comments driver maximum data rate 12 15 differential output delay t dd 1 22 35 ns r l = 60 ?, c l1 = c l2 = 15 pf (see figure 6 ) differential output transition time t td 3 11 25 ns r l = 60 ?, c l1 = c l2 = 15 pf (see figure 6 ) propagation delay from low to high level t plh 7 23 35 ns r l = 27 ? (see figure 7 ) from high to low level t phl 7 23 35 ns r l = 27 ? (see figure 7 ) |t plh ? t phl | propagation delay skew t pds C1.4 8 ns r l = 27 ? (see figure 7 ) enable/d isable timing enable time to low level t pzl 42 90 ns r l = 110 ? (see figure 9 ) enable time to high level t pzh 42 90 ns r l = 110 ? (see figure 8 ) disable time from low level t plz 35 80 ns r l = 110 ? (see figure 9 ) disable time from high level t phz 35 80 ns r l = 110 ? (see figure 8 ) enable time from shutdown to low level t psl 650 900 ns r l = 110 ? (see figure 9 ) en able time from shutdown to high level t psh 650 900 ns r l = 110 ? (see figure 8 ) receiver propagation delay from low to high level t rplh 25 62 90 ns v id = 0 v to 3.0 v, c l = 15 pf (see figur e 10 ) from high to low level t rphl 25 62 90 ns v id = 0 v to 3.0 v, c l = 15 pf (see figure 10 ) |t rplh ? t rphl | propagation delay skew t rpds 6 10 ns v id = 0 v to 3.0 v, c l = 15 pf (see figure 10 ) enab le/disable timing enable time to low level t rpzl 25 50 ns c l = 15 pf (see figure 11 ) enable time to high level t rpzh 25 50 ns c l = 15 pf (see figure 11 ) disable time from low level t rplz 25 45 ns c l = 15 pf (see figure 11 ) disable time from high level t rphz 25 45 ns c l = 15 pf (see figure 11 ) enable time from shutdown to low level t rpsl 720 1400 ns c l = 15 pf (see figure 11 ) enable time from shutdown to high level t rpsh 720 1400 ns c l = 15 pf (see figure 11 ) time to shutdown 1 t shdn 80 190 300 ns 1 the transceivers are put into shutdown mode by bringing the re high and the de low. if the inputs are in this state for less than 80 ns, the parts are guaranteed not to enter shutdown. if the parts are in this state for 300 ns or more, the parts are guaranteed to enter shutdown.
adm3485e rev. d | page 5 of 16 absolute maximum rat ings t a = 25c, unless otherwise noted. table 3. parameter values v cc to gnd C 0.3 v to +6 v digital input/output voltage (de, re , di) C 0.3 v to +6 v receiver output voltage (ro) C 0.3 v to (v cc + 0.3 v) driver output (a, b )/ receiver input (a, b) voltage ?8 v to +13 v driver output current 250 ma power dissipation (8- lead soic _n) 650 mw operating temperature range C 40c to +85c storage temperature range C65 c to +150 c lead temperature, soldering (10 sec) 300c vapor phase (60 sec) 215c infrared (15 sec) 220c esd rating human body model (a , b) 15 kv 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 conditi ons 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. thermal resistance ja is specified for the worst - case conditions, that is, a device soldered in a circuit board for surface - mount packages. table 4 . thermal resistance package type ja unit 8- lead soic_n 158 c/w esd caution
adm3485e rev. d | page 6 of 16 pin configurati on and pin function des criptions ro 1 re 2 de 3 di 4 v cc 8 b 7 a 6 gnd 5 adm3485e top view (not to scale) 03338-002 figure 2 . soic _n pin configuration (r - 8) table 5 . pin function descriptions mnemonic pin number description ro 1 receiver output. when enabled , if a > b by 200 mv, th en r o = h igh. if a < b by 200 mv, then ro = l ow. re 2 receiver output enable. with re low, the receiver output ( ro ) is enabled. with re high, the output goes into a high impedance state . if re is high and de is low, the adm3485e enters a shutdown state. de 3 driver output enable. a high level enables the driver differential outputs a and b. a low level places it in a high impedance state. di 4 driver input. when the driver is enabled, a logic low on di forces a low and b high, while a logic high on di forces a high and b low. gnd 5 ground connection, 0 v. a 6 noninverting receiver input a/driver output a. b 7 inverting receiver input b/driver output b. v cc 8 power supply, 3.3 v 0.3 v.
adm3485e rev. d | page 7 of 16 test circuits and sw itching characterist ics v oc r l /2 r l /2 b a v od 03338-037 figure 3 . driver differential output voltage and common - mode output voltage r l 375? 375? v od v cm = ?7v to +12v d v cc 03338-038 figure 4 . driver differential output voltage with varying common - mode voltage v oh i oh (?) v id r 0 i ol (+) v ol 03338-039 figure 5 . receiver output voltage high and output voltage low in out +1.5v +1.5v +3v 0v +2v C2v t dd t dd t td t td 50% 50% 10% 10% 90% 90% d generator 1 v cc 50? c l r l = 60? c l = 15pf 2 out 1 ppr = 250khz, 50% duty cycle, t r 6.0ns, z o = 50. 2 c l includes probe and stray capacitance. 03338-040 figure 6 . driver differential output delay and transition times 3v 0v v oh v ol v oh v ol v om v om v om v om in a out b out 1.5v 1.5v t plh t phl t phl t plh d v om r l = 27 ? out c l = 15pf 2 generator 1 v cc 50? s1 v om = v oh + v ol 2 1.5v 1 ppr = 250khz, 50% duty cycle, t r 6.0ns, z o = 50. 2 c l includes probe and stray capacitance. 03338-041 figure 7 . drive r propagation delays d out c l = 50pf 2 generator 1 50? s1 v om = v oh + v ol 2 1.5v r l = 110 ? 0v or 3v 1 ppr = 250khz, 50% duty cycle, t r 6.0ns, z o = 50. 2 c l includes probe and stray capacitance. 0v v oh 0v 3v 1.5v 1.5v 0.25v in out v om t pzh t phz 03338-042 figure 8 . driver enable and disable times (t pzh , t psh , t phz )
adm3485e rev. d | page 8 of 16 v ol v cc 0v 3v 0.25v in out 1.5v 1.5v t psl t plz v om d out c l = 50pf 2 generator 1 50? s1 0v or 3v v cc r l = 110 ? 1 ppr = 250khz, 50% duty cycle, t r 6.0ns, z o = 50. 2 c l includes probe and stray capacitance. 03338-043 figure 9 . driver enable and disable times (t pzl , t psl , t plz ) 3v 0v v cc 0v in out v om v om 1.5v 1.5v t rphl t rplh generator 1 50? c l = 15pf 2 r 1.5v 0v v om = v cc 2 out v id 1 ppr = 250khz, 50% duty cycle, t r 6.0ns, z o = 50. 2 c l includes probe and stray capacitance. 03338-044 figure 10 . receiver prop agation delays +3v 0v v oh 0v s1 open s2 closed s3 = +1.5v s1 c losed s2 open s3 = ?1.5v s1 open s2 closed s3 = +1.5v s1 closed s2 open s3 = ?1.5v +3v 0v v cc v ol +3v 0v v cc v ol +3v 0v v oh 0v +1.5v +1.5v +1.5v in out in out in out in out t rpzl t rpsl t rplz t rphz +0.25v +0.25v +1.5v +1.5v +1.5v t rpzh t rpsh r generator 1 50? c l 2 s3 s1 s2 v cc +1.5v ?1.5v v id 1k? 1 ppr = 250khz, 50% duty cycle, t r 6.0ns, z o = 50. 2 c l includes probe and stray capacitance. 03338-045 figure 11 . receiver enable and disable times
adm3485e rev. d | page 9 of 16 typical performance characteristics 25 0 0 3.5 output low voltage ( v) output current (ma) 0.5 1.0 1.5 2.0 2.5 3.0 20 15 10 5 03338-051 figure 12 . output current vs. receiver output low voltage ?18 0 0 3.5 output high voltage ( v) output current (ma) 0.5 1.0 1.5 2.0 2.5 3.0 ?16 ?14 ?12 ?10 ?8 ?6 ?4 ?2 03338-052 figure 13 . output current vs. receiver output high voltage temperature (c) output high voltage (v) 3.00 3.05 3.10 3.15 3.20 3.25 3.30 ?50 ?25 0 25 50 75 i ro = ?1.5ma 03338-053 figure 14 . receiver output high voltage vs. temperature temperature (c) output low voltage (v) 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 ?40 10 60 85 i ro = 2.5ma 03338-054 figure 15 . receiver output low voltage vs. temperature 100 0 0 3.5 differential output voltage ( v) output current (ma) 0.5 1.0 1.5 2.0 2.5 3.0 90 80 70 60 50 40 30 20 10 03338-055 figure 16 . dr iver output current vs. differential output voltage 2.6 1.6 ?50 temperature (c) differential output voltage (v) ?25 0 25 50 75 2.5 2.4 2.3 2.2 2.1 2.0 1.9 1.8 1.7 r l = 54 03338-056 figure 17 . driver differential output voltage vs. temperature
adm3485e rev. d | page 10 of 16 output low voltage (v) output current (ma) 0 20 40 60 80 100 120 0 2 4 6 8 10 12 03338-057 figure 18 . output current vs. driver output low voltage output high voltage (v) output current (ma) 0 20 40 60 80 100 120 ?7 ?6 ?5 ?4 ?3 ?2 ?1 0 1 2 3 4 03338-058 figure 19 . output current vs. driver output high voltage 1.2 0.5 ?40 temperature (c) supply current (ma) ?10 20 50 80 1.1 1.0 0.9 0.8 0.7 0.6 03338-059 figure 20 . supply current vs. temperature 0.9 0 ?50 temperature (c) shutdown current ( a) ?25 0 25 50 75 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 03338-060 figure 21 . shutdown current vs. temperature ch1 1.0v ? ch2 1.0v ? it 400ps/pt ch3 2.0v ? m20n s 1.25gs/s a ch3 1.44v 3 ch1 ch2 a b di 03338-061 figure 22 . driver propagation delay ch3 2.0v 4ns/pt ma th1 2.01v 200n s m200ns 250ms/s a ch2 1.24v 3 m1 v a ? v b ro ? 03338-062 figure 23 . receiver propagation delay, driven by external rs - 485 device
adm3485e rev. d | page 11 of 16 standards and testin g table 6 compares rs - 422 and rs - 485 interface standards, and table 7 and table 8 show transmitting and receiving truth tables. table 6. specification rs - 422 rs - 485 transmission type differential differential maximum data rate 10 m bps 10 m bps maximum cable length 4000 ft 4000 ft minimum driver output voltage 2 v 1.5 v driver load impedance 100 ? 54 ? receiver input resistance 4 k ? min 12 k ? min receiver input sensitivity 200 mv 200 mv receiver input voltage range ?7 v to +7 v ?7 v to +12 v number of drivers/receivers p er line 1/10 32/32 table 7 . transmitting tr uth table transmitting inputs transmitting outputs re de di b a x 1 1 1 0 1 x 1 1 0 1 0 0 0 x 1 high -z 2 high -z 2 1 0 x 1 high -z 2 high -z 2 1 x = don't care. 2 high - z = high impedance. table 8 . receiving truth t able receiving inputs receiving outputs re de a C b ro 0 x 1 > +0.2 v 1 0 x 1 < C 0.2 v 0 0 x 1 inputs o pen 1 1 x 1 x 1 high -z 2 1 x = don't care. 2 high - z = high impedance. esd testing two coupling methods are used for esd testing, con tact discharge and air - gap discharge. contact discharge calls for a direct connection to the unit being tested. air - gap discharge uses a higher test voltage but does not make direct contact with the unit under test. with air - gap discharge, the discharge gu n is moved toward the unit under test, developing an arc across the air gap, hence the term air - gap discharge. this method is influenced by humidity, temperature, barometric pressure, distance, and rate of closure of the discharge gun. the contact discharg e method, while less realistic, is more repeatable and is gaining acceptance and preference over the air - gap method. although very little energy is contained within an esd pulse, the extremely fast rise time, coupled with high voltages, can cause failures in unprotected semiconductors. catastrophic destruction can occur immediately as a result of arcing or heating. even if catastrophic failure does not occur immediately, the device can suffer from parametric degradation, which can result in degraded performance. the cumulative effects of continuous exposure can eventually lead to complete failure. i/o lines are particularly vulnerable to esd damage. simply touching or plugging in an i/o cable can result in a static discharge that can damage or completely destroy the interface product connected to the i/o port. it is extremely important, therefore, to have high levels of esd protection on the i/o lines. the esd discharge could induce latch - up in the device under test, so it is important that esd testing on th e i/o pins be carried out while device power is applied. this type of testing is more representative of a real - world i/o discharge , where the equipment is operating normally when the discharge occurs. table 9 . esd test results esd t est method i/o pins h uman body model 15 kv 100% 90% 36.8% 10% t rl t dl i peak time t 03338-023 figure 24 . human body model current waveform
adm3485e rev. d | page 12 of 16 applications informa tion differential data tr ansmission differential data transmission is used to reliably transmit data at high rate s over long distances and through noisy environ - ments. differential transmission nullifies the effects of ground shifts and noise signals that appear as common - mode voltages on the line. two main standards that specify the electrical characteristics of tra nsceivers used in differential data transmission are approved by the electroni cs industries association (eia) . the rs - 422 standard specifies data rates up to 10 mbps and line lengths up to 4000 feet. a single driver can drive a transmission line with up to 10 receivers. the rs - 485 standard was defined to cater to true multipoint communications. this standard meets or exceeds all the r equirements of rs - 422 but also allows multiple drivers and receivers to be connected to a single bus. an extended common - mode range of ?7 v to +12 v is defined. the most significant difference between rs - 422 and rs - 485 is the fact that under the rs - 485 standard the drivers may be disabled, thereby allowing more than one to be connected to a single line. only one driver should be enabled at a time, but the rs - 485 standard contains additional specifications to guarantee device safety in the event of line contention. cable and data rate the transmission line of choice for rs - 485 communications is a twisted pair. twisted - pair cable t ends to cancel common - mode noise and also causes cancellation of the magnetic fields generated by the current flowing through each wire, thereby reducing the effective inductance of the pair. the adm3485e is designed for bidirectional data communi - cations on multipoint transmission lines. a typical application showing a multipoint transmission network is illustrated in figure 25 . only one driver can transmit at a particular time, but multiple receivers may be enabled simultaneousl y. as with any transmission line, it is important that reflections are minimized. this can be achieved by terminating the extreme ends of the line using resistors equal to the characteristic impe - dance of the line. stub lengths of f the main line must also be kept as short as possible. a properly terminated transmission line appears purely resistive to the driver. receiver open - circuit fail - safe the receiver input includes a fail - safe feature that guarantees a logic high on the receiver when the inputs are open circuit or floating. table 10 . rs - 422 and rs - 485 interface standards specification rs- 422 rs- 485 transmission type differential differential maximum cable length 4000 ft 4000 ft minimum driver output voltage 2 v 1.5 v dr iver load impedance 100 ? 54 ? receiver input resistance 4 k ? min 12 k ? min receiver input sensitivity 200 mv 200 mv receiver input voltage range ? 7 v to +7 v ? 7 v to +12 v b a r d ro re di de adm3485e b a r d ro re di de adm3485e b a r d ro re di de adm3485e b a r d ro re di de adm3485e maximum number of transceivers on bus: 50 03338-027 figure 25 . multipoint transmission network
adm3485e rev. d | page 13 of 16 outl ine dimensions controlling dimensions are i n millimeters; inch dimensions (in parentheses) a re rounded-off millimeter equivalents for referen ce only and are not appropriate for use in des ign. compliant to jedec standards ms-012-aa 012407-a 0.25 (0.0098) 0.17 (0.0067) 1.27 (0.0500) 0.40 (0.0157) 0.50 (0.0196) 0.25 (0.0099) 45 8 0 1.75 (0.0688) 1.35 (0.0532) seating plane 0.25 (0.0098) 0.10 (0.0040) 4 1 8 5 5.00 (0.1968) 4.80 (0.1890) 4.00 (0.1574) 3.80 (0.1497) 1.27 (0.0500) bsc 6.20 (0.2441) 5.80 (0.2284) 0.51 (0.0201) 0.31 (0.0122) coplanarity 0.10 figure 26 . 8 - lead standard small outline package [soic _n ] narrow body (r - 8) dimensions shown in millimeters and (inches) ordering guide model 1 temperature range package description package option adm3485ear C40 c to +85c 8- lead standard small outline package [soic_n] r-8 adm3485ear- reel7 C 40c to +85c 8- lead standard small outline package [soic_n] r-8 adm3485ear- reel C 40c to +85c 8- lead standard small outline package [soic_n] r-8 adm3485earz C 40c to +85c 8- lead standard small outline package [soic_n] r-8 adm3485earz- reel7 C 40c to +85c 8- lead standard small outline package [soic_n] r-8 adm3485earz- reel C 40c to +85c 8- lead standard small outline package [soic_n] r-8 1 z = rohs compliant part.
adm3485e rev. d | page 14 of 16 notes
adm3485e rev. d | page 15 of 16 notes
adm3485e rev. d | page 16 of 16 notes ?2000-2010 analog devices, inc. all rights reserved. trademarks and registered trademarks are the prop erty of their respective owners. d03338-0-8/10(d)

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