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general description the max3440eCmax3444e fault-protected rs-485 and j1708 transceivers feature 60v protection from signal faults on communication bus lines. each device contains one differential line driver with three-state output and one differential line receiver with three-state input. the 1/4-unit- load receiver input impedance allows up to 128 transceiv - ers on a single bus. the devices operate from a 5v supply at data rates of up to 10mbps. true fail-safe inputs guar - antee a logic-high receiver output when the receiver inputs are open, shorted, or connected to an idle data line. hot-swap circuitry eliminates false transitions on the data bus during circuit initialization or connection to a live backplane. short-circuit current-limiting and thermal shut - down circuitry protect the driver against excessive power dissipation, and on-chip 15kv esd protection eliminates costly external protection devices. the max3440eCmax3444e are available in 8-pin so and pdip packages and are specified over industrial and automotive temperature ranges. applications rs-422/rs-485 communications industrial networks telecommunications systems hvac controls features 15kv esd protection 60v fault protection guaranteed 10mbps data rate (max3441e/max3443e) hot swappable for telecom applications true fail-safe receiver inputs enhanced slew-rate-limiting facilitates error-free data transmission (max3440e/max3442e/max3444e) allow up to 128 transceivers on the bus -7v to +12v common-mode input range automotive temperature range (-40c to +125c) industry-standard pinout 19-2666; rev 3; 4/14 +denotes a lead(pb)-free/rohs-compliant package. ordering information continued at end of data sheet. part temp range pin-package max3440e esa+ -40c to +85c 8 so MAX3440EEPA+ -40c to +85c 8 pdip max3440easa+ -40c to +125c 8 so max3440eapa+ -40c to +125c 8 pdip ordering information pin configurations and typical operating circuits continued at end of data sheet. part type data rate (mbps) low-power shutdown receiver/driver enable transceivers on bus hot swap max3440e rs-485 0.25 no yes 128 yes max3441e rs-485 2.5 to 10 no yes 128 yes max3442e rs-485 0.25 yes yes 128 yes max3443e rs-485 2.5 to 10 yes yes 128 yes max3444e j1708 0.25 yes yes 128 yes (only re ) top view 1 2 3 4 8 5 v cc gnd di de/re ro fault r d rt rt 7 6 d r de/re fault di ro a b 1 2 3 4 8 7 6 5 v cc b a gnd di de/re ro fault + + dip/so dip/so b a max3440e max3441e r d selector guide pin confgurations and typical operating circuits max3440eCmax3444e 15kv esd-protected, 60v fault-protected, 10mbps, fail-safe rs-485/j1708 transceivers
voltages referenced to gnd v cc ........................................................................................ +7v fault, de/re, re , de, de , di, txd ...... -0.3v to (v cc + 0.3v) a, b (note 1) ....................................................................... 60v ro ............................................................ -0.3v to (v cc + 0.3v) short-circuit duration (ro, a, b) .............................. continuous continuous power dissipation (t a = +70c) so (derate 5.9mw/c above +70c) .......................... 471mw pdip (derate 9.09mw/c above +70c) ..................... 727mw operating temperature ranges max344_ee_ _ .............................................. -40c to +85c max344_ea_ _ ............................................ -40c to +125c storage temperature range ............................ -65c to +150c junction temperature ...................................................... +150c lead temperature (soldering, 10s) ................................. +300c soldering temperature (reflow) ....................................... +260c (v cc = +4.75v to +5.25v, t a = t min to t max , unless otherwise noted. typical values are at v cc = +5v and t a = +25c.) parameter symbol conditions min typ max units driver differential driver output v od figure 1, r l = 100? 2 v cc v figure 1, r l = 54? 1.5 v cc change in magnitude of differential output voltage ?v od figure 1, r l = 100? or 54? (note 2) 0.2 v driver common-mode output voltage v oc figure 1, r l = 100? or 54? v cc / 2 3 v change in magnitude of common-mode voltage ?v oc figure 1, r l = 100? or 54? (note 2) 0.2 v driver logic driver input high voltage v dih 2 v driver input low voltage v dil 0.8 v driver input current i din 2 a driver short-circuit output current (note 3) i osd 0v v out +12v +350 ma -7v v out v cc -350 driver short-circuit foldback output current i osdf (v cc - 1v) v out +12v (note 3) +25 ma -7v v out +1v (note 3) -25 receiver input current i a,b a, b v cc = gnd, v a , b = 12v 250 a v a , b = -7v -150 v a , b = 60v 6 ma receiver differential threshold voltage v th -7v v cm +12v -200 -50 mv receiver input hysteresis ?v th 25 mv maxim integrated 2 dc electrical characteristics stresses beyond those listed under absolute maximum ratings may cause permanent damage to the device. these are stress rating s only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. exposure to ab solute maximum rating conditions for extended periods may affect device reliability. note 1: a, b must be terminated with 54 ? or 100 ? to guarantee 60v fault protection. absolute maximum ratings www.maximintegrated.com max3440eCmax3444e 15kv esd-protected, 60v fault-protected, 10mbps, fail-safe rs-485/j1708 transceivers
(v cc = +4.75v to +5.25v, t a = t min to t max , unless otherwise noted. typical values are at v cc = +5v and t a = +25c.) (v cc = +4.75v to +5.25v, t a = t min to t max , unless otherwise noted. typical values are at v cc = +5v and t a = +25c.) parameter symbol conditions min typ max units overvoltage protection a, b; r source = 0, r l = 54? 60 v esd protection a, b human body model 15 kv fault detection receiver differential threshold f diph v cm = 0v, high limit 270 450 mv receiver differential threshold f dipl v cm = 0v, low limit -450 -270 mv fault-detection common-mode input voltage positive 12 v fault-detection common-mode input voltage negative -7 v parameter symbol conditions min typ max units receiver logic output high voltage v oh figure 2, i oh = -1.6ma v cc C 0.6 v output low voltage v ol figure 2, i ol = 1ma 0.4 v three-state output current at receiver i ozr 0v v a , b v cc 1 a receiver input resistance r in -7v v cm +12v 48 k ? receiver output short-circuit current i osr 0v v ro v cc 95 ma control control input high voltage v cih de, de, re, de/re 2 v input current latch during first rising edge i in de, de/re, re 90 a supply current normal operation i q no load, di = v cc or gnd max3440e (de/re = v cc ), max3442e (de = v cc , re = gnd), max3444e (de = re = gnd) 30 ma max3441e (de/re = v cc ), max3443e (de = v cc , re = gnd) 10 supply current in shutdown mode i shdn de = gnd, re = v cc (max3442e/ max3443e) 20 a de = gnd, re = v cc , t a = +25c (max3442e/max3443e) 10 de = re = v cc (max3444e) 100 de = re = v cc , t a = +25c (max3444e) 10 supply current with output shorted to 60v i shrt de = gnd, re = gnd, no load output in three-state (max3443e) 15 ma maxim integrated 3 3urwhfwlrq6shflfdwlrqv dc electrical characteristics (continued) www.maximintegrated.com max3440eCmax3444e 15kv esd-protected, 60v fault-protected, 10mbps, fail-safe rs-485/j1708 transceivers
(v cc = +4.75v to +5.25v, t a = t min to t max , unless otherwise noted. typical values are at v cc = +5v and t a = +25c.) parameter symbol conditions min typ max units driver propagation delay t plha , t plhb max3440e/max3442e, figure 3, r l = 54?, c l = 50pf 2000 ns max3444e, r diff = 60?, c diff = 100pf driver differential propagation delay t dplh , t dphl figure 4, r l = 54?, c l = 50pf 2000 ns driver differential output transition time t lh ,t h l figure 4, r l = 54?, c l = 50pf 200 2000 ns driver output skew t skewab , t skewba r l = 54?, c l = 50pf, t skewab = |t plha - t phlb |, t skewba = |t plhb - t phla | 350 ns differential driver output skew t dskew r l = 54?, c l = 50pf, t dskew = |t dplh - t dphl | 200 ns maximum data rate f max 250 kbps driver enable time to output high t pdzh figure 5, r l = 500?, c l = 50pf 2000 ns driver disable time from output high t pdhz figure 5, r l = 500?, c l = 50pf 2000 ns driver enable time from shutdown to output high t pdhs figure 5, r l = 500?, c l = 50pf (max3442e/max3444e) 4.2 s driver enable time to output low t pdzl figure 6, r l = 500?, c l = 50pf 2000 ns driver disable time from output low t pdlz figure 6, r l = 500?, c l = 50pf 2000 ns driver enable time from shutdown to output low t pdls figure 6, r l = 500?, c l = 50pf (max3442e/max3444e) 4.2 s driver time to shutdown t shdn r l = 500?, c l = 50pf (max3442e/max3444e) 800 ns receiver propagation delay t rplh , t rphl figure 7, c l = 20pf, v id = 2v, v cm = 0v 2000 ns receiver output skew t rskew c l = 20pf, t rskew = |t rplh - t rphl | 200 ns receiver enable time to output high t rpzh figure 8, r l = 1k?, c l = 20pf 2000 ns receiver disable time from output high t rphz figure 8, r l = 1k?, c l = 20pf 2000 ns receiver wake time from shutdown t rpwake figure 8, r l = 1?, c l = 20pf (max3442e/max3444e) 4.2 s receiver enable time to output low t rpzl figure 8, r l = 1k?, c l = 20pf 2000 ns receiver disable time from output low t rplz figure 8, r l = 1?, c l = 20pf 2000 ns receiver time to shutdown t shdn r l = 50?, c l = 50pf (max3442e/max3444e) 800 ns maxim integrated 4 switching characteristics (max3440e/max3442e/max3444e) www.maximintegrated.com max3440eCmax3444e 15kv esd-protected, 60v fault-protected, 10mbps, fail-safe rs-485/j1708 transceivers
note 2: ?v od and ?v oc are the changes in v od and v oc , respectively, when the di input changes state. note 3: the short-circuit output current applies to peak current just before foldback current limiting; the short-circuit foldback output current applies during current limiting to allow a recovery from bus contention. (v cc = +4.75v to +5.25v, t a = t min to t max , unless otherwise noted. typical values are at v cc = +5v and t a = +25c.) parameter symbol conditions min typ max units driver propagation delay t plha , t plhb figure 3, r l = 27?, c l = 50pf 60 ns driver differential propagation delay t dplh , t dphl figure 4, r l = 54?, c l = 50pf 60 ns driver differential output transition time t lh ,t hl figure 4, r l = 54?, c l = 50pf 25 ns driver output skew t skewab , t skewba r l = 54?, c l = 50pf, t skewab = |t plha - t phlb |, t skewba = |t plhb - t phla | 10 ns differential driver output skew t dskew r l = 54?, c l = 50pf, t dskew = |t dplh - t dphl | 10 ns maximum data rate f max 10 mbps driver enable time to output high t pdzh figure 5, r l = 500?, c l = 50pf 1200 ns driver disable time from output high t pdhz figure 5, r l = 500?, c l = 50pf 1200 ns driver enable time from shutdown to output high t pdhs figure 5, r l = 500?, c l = 50pf (max3443e) 4.2 s driver enable time to output low t pdzl figure 6, r l = 500?, c l = 50pf 1200 ns driver disable time from output low t pdlz figure 6, r l = 500?, c l = 50pf 1200 ns driver enable time from shutdown to output low t pdls figure 6, r l = 500?, c l = 50pf (max3443e) 4.2 s driver time to shutdown t shdn figure 6, r l = 500?, c l = 50pf (max3443e) 800 ns receiver propagation delay t rplh , t rphl figure 7, c l = 20pf, v id = 2v, v cm = 0v 85 ns receiver output skew t rskew c l = 20pf, t rskew = |t rplh - t rphl | 15 ns receiver enable time to output high t rpzh figure 8, r l = 1k?, c l = 20pf 400 ns receiver disable time from output high t rphz figure 8, r l = 1k?, c l = 20pf 400 ns receiver wake time from shutdown t rpwake figure 8, r l = 1k?, c l = 20pf (max3443e) 4.2 s receiver enable wake time from shutdown t rpsh figure 8, r l = 1k?, c l = 20pf 400 ns receiver disable time from output low t rplz figure 8, r l = 1k?, c l = 20pf 400 ns receiver time to shutdown t shdn r l = 500?, c l = 50pf (max3443e) 800 ns maxim integrated 5 switching characteristics (max3441e/max3443e) www.maximintegrated.com max3440eCmax3444e 15kv esd-protected, 60v fault-protected, 10mbps, fail-safe rs-485/j1708 transceivers
(v cc = +5v, t a = +25c, unless otherwise noted.) a, b current vs. a, b voltage (to ground) max3443e toc09 a, b voltage (v) a, b current ( a) 40 30 60 50 -50 -40 -30 -10 0 10 -20 20 -800 -400 -1600 -2000 r l = 54? -1200 0 400 800 1200 1600 2000 -60 driver disabled, receiver enabled differential output voltage vs. temperature max3443e toc08 temperature (c) differential output voltage (v) 110 95 65 80 -10 5 20 35 50 -25 0.5 1.0 1.5 2.0 2.5 3.0 3.5 0 -40 125 r l = 100? r l = 54? max3441e/max3443e driver output current vs. differential output voltage max3443e toc07 differential output voltage (v a - v b ) (v) driver output current (ma) 0.5 1.0 1.5 2.5 3.0 3.5 2.0 10 20 30 40 50 60 70 80 0 0 receiver output voltage vs. temperature max3443e toc06 temperature (c) receiver output voltage (v) 110 95 65 80 -10 5 20 35 50 -25 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 0 -40 125 v ol , i out = -10ma v oh , i out = +10ma receiver output current vs. output high voltage max3443e toc05 output high voltage (v) receiver output current (ma) 5.0 4.5 0.5 1.0 1.5 2.5 3.0 3.5 2.0 4.0 5 10 15 20 25 30 35 40 0 0 receiver output current vs. output low voltage max3443e toc04 output low voltage (v) receiver output current (ma) 5.0 4.5 0.5 1.0 1.5 2.5 3.0 3.5 2.0 4.0 5 10 15 20 25 30 35 40 0 0 shutdown supply current vs. temperature max3443e toc03 temperature (c) supply current (a) 110 95 80 65 50 35 20 5 -10 -25 0.1 1 10 0.01 -40 125 max3442e/max3443e/max3444e no-load supply current vs. temperature max3440e toc02 temperature (c) supply current (ma) 110 95 80 65 50 35 20 5 -10 -25 4 8 12 16 20 24 0 -40 125 max3440e/max3442e/max3444e driver and receiver enabled driver disabled, receiver enabled no-load supply current vs. temperature max3440e toc01 wtemperature (c) supply current (ma) 110 95 80 65 50 35 20 5 -10 -25 1 2 3 4 5 6 0 -40 125 driver and receiver enabled max3441e/max3443e driver disabled, receiver enabled maxim integrated g 6 7slfdo2shudwlqjkdudfwhulvwlfv www.maximintegrated.com max3440eCmax3444e 15kv esd-protected, 60v fault-protected, 10mbps, fail-safe rs-485/j1708 transceivers
figure 4. driver differential output delay and transition times figure 3. driver propagation times figure 2. receiver v oh and v ol figure 1. driver v od and v oc v cc 50? r l c l = 50pf (note 5) generator (note 4) d di out c l c l t dplh t dphl t lh 50% 1.5v 10% (a?b) di 90% 50% 1.5v 10% 90% 3v 0 a 2.0v t hl a -2.0v a b v cc v om 3v 0 v oh v om v om v om v om v ol v oh v ol 50? r l c l = 50pf (note 5) generator (note 4) d di t plha 1.5v a b out s1 di 1.5v t phla t phlb t plhb a 1.5v v oh + v ol 2 v om = a b 2 r ro 0 v oh i oh (-) i ol (+) v ol v id a b v cc d v od v oc 2 r l 2 r l di a b maxim integrated g 7 test circuits and waveforms www.maximintegrated.com max3440eCmax3444e 15kv esd-protected, 60v fault-protected, 10mbps, fail-safe rs-485/j1708 transceivers
figure 7. receiver propagation delay figure 6. driver enable and disable times figure 5. driver enable and disable times 50? generator (note 4) c l = 20pf (note 5) v id r r o t rplh 1.0v ro 1.0v 0 (a?b) 1.0v 2.0v 0 t rphl v cc v om v om 0 a b a, b de v cc 3v 0 v cc v ol v om t pdls 1.5v 0.25v 1.5v t pdlz 50? generator (note 4) d 0 or 3v a, b s1 c l = 50pf (note 5) r l = 500? di de a b t pdzl 50w generator (note 4) a 1.5v v oh + v ol 2 v om = 3v 0 v oh v om 0 d 0 or 3v t pdhs t pdhz 1.5v 0.25v a, b a, b s1 de 1.5v c l = 50pf (note 5) r l = 500w di a b de t pdzh maxim integrated g 8 test circuits and waveforms (continued) www.maximintegrated.com max3440eCmax3444e 15kv esd-protected, 60v fault-protected, 10mbps, fail-safe rs-485/j1708 transceivers
note 4: the input pulse is supplied by a generator with the following characteristics: f = 5mhz, 50% duty cycle; tr 6ns; z0 = 50 ? . note 5: c l includes probe and stray capacitance. figure 8. receiver enable and disable times 50? generator (note 4) c l = 20pf (note 5) v cc 3v 0 v cc v ol r 1.5v -1.5v v id 1.5v ro s1 s2 1k? re 1.5v s1 closed s2 open v s3 = -1.5v t rpzl t rpsl 3v 0 v oh 0 1.5v re 1.5v s1 open s2 closed v s3 = 1.5v t rpzh t rpsh t rpwake 3v 0 v cc v ol 0.5v ro re 1.5v s1 closed s2 open v s3 = -1.5v t rplz 3v 0 v oh 0 0.5v 1.5v ro re s1 open s2 closed v s3 = 1.5v t rphz s3 r o a b ro maxim integrated 9 test circuits and waveforms (continued) www.maximintegrated.com max3440eCmax3444e 15kv esd-protected, 60v fault-protected, 10mbps, fail-safe rs-485/j1708 transceivers
pin name function max3440e max3441e max3442e max3443e max3444e 1 fault fault output. 1 = fault; 0 = normal operation a or b under the following conditions: ? a-b differential <200mv ? a shorted to b ? a shorted to a voltage within the common-mode range (detected only when the driver is enabled) ? b shorted to a voltage within the common-mode range (detected only when the driver is enabled) ? a or b outside the common-mode range 2 1 1 ro receiver output. if receiver enabled and (a-b) -50mv, ro = high; if (a-b) -200mv, ro = low. 2 2 re receiver output enable. pull re low to enable ro. 3 de driver output enable. pull de low to enable the outputs force de high to three-state the outputs. drive re and de high to enter low-power shutdown mode. 3 de/re driver/receiver output enable. pull de/re low to three- state the driver output and enable ro. force de/re high to enable driver output and three-state ro 3 de driver output enable. force de high to enable driver. pull de low to three-state the driver output. drive re high and pull de low to enter low-power shutdown mode. 4 4 di driver input. a logic-low on di forces the noninverting output low and the inverting output high. a logic-high on di forces the noninverting output high and the inverting output low. 4 txd j1708 input. a logic-low on txd forces outputs a and b to the dominant state. a logic-high on txd forces outputs a and b to the recessive state. 5 5 5 gnd ground 6 6 6 a noninverting receiver input/driver output 7 7 7 b inverting receiver input/driver output 8 8 8 v cc positive supply, v cc = +4.75v to +5.25v maxim integrated 10 pin description www.maximintegrated.com max3440eCmax3444e 15kv esd-protected, 60v fault-protected, 10mbps, fail-safe rs-485/j1708 transceivers
x = dont care. x = dont care. x = dont care. x = dont care. x = dont care. note 1: receiver output may oscillate with this differential input condition. table 5. max3440e/max3441e (rs-485/rs-422) table 4. max3444e (j1708) application table 3. max3442e/max3443e (rs-485/rs-422) table 2. max3440e/max3441e (rs-485/rs-422) table 1. max3440e/max3441e fault table receiving inputs outputs de/re (a - b) ro 0 -0.05v 1 0 -0.2v 0 0 open/shorted 1 1 x high-z transmitting inputs outputs conditions txd de a b 0 1 high-z high-z 1 1 high-z high-z 0 0 0 1 dominant state 1 0 high-z high-z recessive state transmitting inputs outputs re de di a b 0 0 x high-z high-z 0 1 0 0 1 0 1 1 1 0 1 0 x shutdown shutdown 1 1 0 0 1 1 1 1 1 0 transmitting inputs outputs de/re di a b 0 x high-z high-z 1 0 0 1 1 1 1 0 inputs outputs fault condition a-b v id differential input voltage common-mode voltage ro fault conditioned by delay 0.45v 12v and -7v 1 0 normal operation <0.45v and 0.27v 1 indeterminate indeterminate <0.27v and -0.05v 1 1 low-input differential voltage -0.05v and -0.2v indeterminate (note 1) 1 low-input differential voltage -0.2v and >-0.27v 0 1 low-input differential voltage -0.27v and >-0.45v 0 indeterminate indeterminate -0.45v 0 0 x <-7v or >+12v indeterminate 1 outside common-mode voltage range maxim integrated 11 function tables www.maximintegrated.com max3440eCmax3444e 15kv esd-protected, 60v fault-protected, 10mbps, fail-safe rs-485/j1708 transceivers
x = dont care. x = dont care. detailed description the max3440eCmax3444e fault-protected transceivers for rs-485/rs-422 and j1708 communication contain one driver and one receiver. these devices feature fail- safe circuitry, which guarantees a logic-high receiver out - put when the receiver inputs are open or shorted, or when they are connected to a terminated transmission line with all drivers disabled (see the true fail-safe section). all devices have a hot-swap input structure that prevents disturbances on the differential signal lines when a cir - cuit board is plugged into a hot backplane (see the hot- swap capability section). the max3440e/max3442e/ max3444e feature a reduced slew-rate driver that mini - mizes emi and reduces reflections caused by improperly terminated cables, allowing error-free data transmission up to 250kbps (see the r educed emi and reflections section). the max3441e/ max3443e drivers are not slew-rate limited, allowing transmit speeds up to 10mbps. driver the driver accepts a single-ended, logic-level input (di) and transfers it to a differential, rs-485/rs-422 level output (a and b). deasserting the driver enable places the driver outputs (a and b) into a high-impedance state. receiver the receiver accepts a differential, rs-485/rs-422 level input (a and b), and transfers it to a single-ended, log - ic-level output (ro). deasserting the receiver enable places the receiver inputs (a and b) into a high-imped - ance state (see tables 1C7). low-power shutdown (max3442e/max3443e/ max3444e) the max3442e/max3443e/max3444e offer a low- power shutdown mode. force de low and re high to shut down the max3442e/max3443e. force de and re high to shut down the max3444e. a time delay of 50ns prevents the device from accidentally entering shutdown due to logic skews when switching between transmit and receive modes. holding de low and re high for at least 800ns guarantees that the max3442e/max3443e enter shutdown. in shutdown, the devices consume a maximum 20a supply current. 60v fault protection the driver outputs/receiver inputs of rs-485 devices in industrial network applications often experience voltage faults resulting from shorts to the power grid that exceed the -7v to +12v range specified in the eia/tia-485 stan - dard. in these applications, ordinary rs-485 devices (typical absolute maximum -8v to +12.5v) require costly external protection devices. to reduce system complexity and eliminate this need for external protection, the driver outputs/receiver inputs of the max3440eCmax3444e withstand voltage faults up to 60v with respect to ground without damage. protection is guaranteed regardless whether the device is active, shut down, or without power. true fail-safe the max3440eCmax3444e use a -50mv to -200mv differential input threshold to ensure true fail-safe receiver inputs. this threshold guarantees the receiver outputs a logic-high for shorted, open, or idle data lines. the -50mv to -200mv threshold complies with the 200mv threshold eia/tia-485 standard. table 7. max3444e (rs-485/rs-422) table 6. max3442e/max3443e (rs-485/rs-422) receiving inputs outputs re de (a - b) ro 0 x -0.05v 1 0 x -0.2v 0 0 x open/shorted 1 1 0 x high-z 1 1 x shutdown receiving inputs outputs re de (a - b) ro 0 x -0.05v 1 0 x -0.2v 0 0 x open/shorted 1 1 1 x high-z 1 0 x shutdown maxim integrated 12 function tables (continued) www.maximintegrated.com max3440eCmax3444e 15kv esd-protected, 60v fault-protected, 10mbps, fail-safe rs-485/j1708 transceivers
15kv esd protection as with all maxim devices, esd-protection structures are incorporated on all pins to protect against esd encoun - tered during handling and assembly. the max3440eC max3444e receiver inputs/driver outputs (a, b) have extra protection against static electricity found in normal operation. maxims engineers have developed state-of- the-art structures to protect these pins against 15kv esd without damage. after an esd event, the max3440eC max3444e continue working without latchup. esd protection can be tested in several ways. the receiver inputs are characterized for protection to 15kv using the human body model. esd test conditions esd performance depends on a number of conditions. contact maxim for a reliability report that documents test setup, methodology, and results. human body model figure 9a shows the human body model, and figure 9b shows the current waveform it generates when dis - charged into a low impedance. this model consists of a 100pf capacitor charged to the esd voltage of inter - est, which is then discharged into the device through a 1.5k? resistor. driver output protection two mechanisms prevent excessive output current and power dissipation caused by faults or bus contention. the first, a foldback current limit on the driver output stage, provides immediate protection against short circuits over the whole common-mode voltage range. the second, a thermal shutdown circuit, forces the driver outputs into a high-impedance state if the die temperature exceeds +160c. normal operation resumes when the die tem - perature cools to +140c, resulting in a pulsed output during continuous short-circuit conditions. figure 9b. human body model current waveform figure 9a. human body esd test model i p 100% 90% 36.8% t rl time t dl current waveform peak-to-peak ringing (not drawn to scale) i r 10% 0 0 amperes charge-current- limit resistor discharge resistance storage capacitor c s 100pf r c 1m? r d 1.5k? high- voltage dc source device under test maxim integrated 13 www.maximintegrated.com max3440eCmax3444e 15kv esd-protected, 60v fault-protected, 10mbps, fail-safe rs-485/j1708 transceivers
hot-swap capability hot-swap inputs inserting circuit boards into a hot, or powered, backplane may cause voltage transients on de, de/re, re , and receiver inputs a and b that can lead to data errors. for example, upon initial circuit board insertion, the processor undergoes a power-up sequence. during this period, the high-impedance state of the output drivers makes them unable to drive the max3440eCmax3444e enable inputs to a defined logic level. meanwhile, leakage currents of up to 10a from the high-impedance output, or capacitively coupled noise from v cc or gnd, could cause an input to drift to an incorrect logic state. to prevent such a condi - tion from occurring, the max3440eCmax3443e feature hot-swap input circuitry on de, de/re, and re to guard against unwanted driver activation during hot-swap situ - ations. the max3444e has hot-swap input circuitry only on re . when v cc rises, an internal pulldown (or pullup for re ) circuit holds de low for at least 10s, and until the current into de exceeds 200a. after the initial power-up sequence, the pulldown circuit becomes transparent, resetting the hot-swap tolerable input. hot-swap input circuitry at the driver-enable input (de), there are two nmos devices, m1 and m2 (figure 10). when v cc ramps from zero, an internal 15s timer turns on m2 and sets the sr latch, which also turns on m1. transistors m2, a 2ma cur - rent sink, and m1, a 100a current sink, pull de to gnd through a 5.6kw resistor. m2 pulls de to the disabled state against an external parasitic capacitance up to 100pf that may drive de high. after 15s, the timer deac - tivates m2 while m1 remains on, holding de low against three-state leakage currents that may drive de high. m1 remains on until an external current source overcomes the required input current. at this time, the sr latch resets m1 and turns off. when m1 turns off, de reverts to a stan - dard, high-impedance cmos input. whenever v cc drops below 1v, the input is reset. a complementary circuit for re uses two pmos devices to pull re to v cc . applications information 128 transceivers on the bus the max3440eCmax3444e transceivers 1/4-unit-load receiver input impedance (48kw) allows up to 128 trans - ceivers connected in parallel on one communication line. connect any combination of these devices, and/or other rs-485 devices, for a maximum of 32-unit loads to the line. reduced emi and refections the max3440e/max3442e/max3444e are slew-rate lim - ited, minimizing emi and reducing reflections caused by improperly terminated cables. figure 11 shows the driver output waveform and its fourier analysis of a 125khz signal transmitted by a max3443e. high-frequency har - monic components with large amplitudes are evident. figure 12 shows the same signal displayed for a max3442e transmitting under the same conditions. figure 12s high-frequency harmonic components are much lower in amplitude, compared with figure 11s, and the potential for emi is significantly reduced. figure 10. simplified structure of the driver enable pin (de) v cc timer timer de (hot swap) 15s 100a m1 m2 5.6k? 2ma maxim integrated 14 www.maximintegrated.com max3440eCmax3444e 15kv esd-protected, 60v fault-protected, 10mbps, fail-safe rs-485/j1708 transceivers
in general, a transmitters rise time relates directly to the length of an unterminated stub, which can be driven with only minor waveform reflections. the following equation expresses this relationship conservatively: length = t rise /(10 x 1.5ns/ft) where t rise is the transmitters rise time. for example, the max3442es rise time is typically 800ns, which results in excellent waveforms with a stub length up to 53ft. a system can work well with longer unterminat - ed stubs, even with severe reflections, if the waveform settles out before the uart samples them. rs-485 applications the max3440eCmax3443e transceivers provide bidirectional data communications on multipoint bus transmission lines. figures 13 and 14 show a typical network applications circuit. the rs-485 standard covers line lengths up to 4000ft. to minimize reflections and reduce data errors, terminate the signal line at both ends in its characteristic impedance, and keep stub lengths off the main line as short as possible. j1708 applications the max3444e is designed for j1708 applications. to configure the max3444e, connect de and re to gnd. connect the signal to be transmitted to txd. terminate the bus with the load circuit as shown in figure 15. the drivers used by sae j1708 are used in a dominant-mode application. de is active low; a high input on de places the outputs in high impedance. when the driver is disabled (txd high or de high), the bus is pulled high by external bias resistors r1 and r2. therefore, a logic level high is encoded as recessive. when all transceivers are idle in this configuration, all receivers output logic high because of the pullup resistor on a and pulldown resistor on b. r1 and r2 provide the bias for the reces - sive state. c1 and c2 combine to form a 6mhz lowpass filter, effective for reducing fm interference. r2, c1, r4, and c2 combine to form a 1.6mhz lowpass filter, effective for reducing am interference. because the bus is untermi - nated, at high frequencies, r3 and r4 perform a pseudo- termination. this makes the implementation more flexible, as no specific termination nodes are required at the ends of the bus. figure 12. driver output waveform and fft plot of max3442e transmitting a 125khz signal figure 11. driver output waveform and fft plot of max3443e transmitting a 125khz signal 5.00mhz 500khz/div 0 20db/div 2v/div 5.00mhz 500khz/div 0 20db/div 2v/div maxim integrated 15 www.maximintegrated.com max3440eCmax3444e 15kv esd-protected, 60v fault-protected, 10mbps, fail-safe rs-485/j1708 transceivers
figure 14. max3442e/max3443e typical rs-485 network figure 13. max3440e/max3441e typical rs-485 network di ro de a b re ro ro ro di di di de de de d d d r r r b b b a a a 120? 120? d r max3442e max3443e re re re di ro de/re a b fault ro ro ro di di di de/re de/re de/re d d d r r r b b b a a a 120? 120? d r max3440e max3441e fault fault fault maxim integrated 16 www.maximintegrated.com max3440eCmax3444e 15kv esd-protected, 60v fault-protected, 10mbps, fail-safe rs-485/j1708 transceivers
+denotes a lead(pb)-free/rohs-compliant package. figure 15. j1708 application circuit part temp range pin-package max3441e esa+ -40c to +85c 8 so max3441eepa+ -40c to +85c 8 pdip max3441easa+ -40c to +125c 8 so max3441eapa+ -40c to +125c 8 pdip max3442e esa+ -40c to +85c 8 so max3442eepa+ -40c to +85c 8 pdip max3442easa+ -40c to +125c 8 so max3442eapa+ -40c to +125c 8 pdip max3443e csa+ 0c to +70c 8 so max3443ecpa+ 0c to +70c 8 pdip max3443eesa+ -40c to +85c 8 so max3443eepa+ -40c to +85c 8 pdip max3443easa+ -40c to +125c 8 so max3443eapa+ -40c to +125c 8 pdip max3444e esa+ -40c to +85c 8 so max3444eepa+ -40c to +85c 8 pdip max3444easa+ -40c to +125c 8 so max3444eapa+ -40c to +125c 8 pdip top view 1 2 3 4 8 5 v cc gnd di de re ro r d rt rt 7 6 d r de re di ro a b 1 2 3 4 8 7 6 5 v cc b a gnd di de re ro dip/so dip/so r d b a max3442e max3443e + + r1 4.7k? r3 47? c1 2.2nf c2 2.2nf r2 4.7k? ro rx tx r4 47? j1708 bus b a txd d r de re max3444e v cc 1 2 3 4 8 5 v cc gnd txd de re ro r d rt rt 7 6 d r de re txd ro a b 1 2 3 4 8 7 6 5 v cc b a gnd txd de re ro dip/so dip/so r d b a max3444e + + maxim integrated 17 pin confgurations and typical operating circuits (continued) ordering information (continued) www.maximintegrated.com max3440eCmax3444e 15kv esd-protected, 60v fault-protected, 10mbps, fail-safe rs-485/j1708 transceivers
package type package code outline no. land pattern no. 8 so s8+4 21-0041 90-0096 maxim integrated 18 package information for the latest package outline information and land patterns (footprints), go to www.maximintegrated.com/packages . note that a +, #, or - in the package code indicates rohs status only. package drawings may show a different suffix character, but the drawing pertains to the package regardless of rohs status. chip information process: bicmos www.maximintegrated.com max3440eCmax3444e 15kv esd-protected, 60v fault-protected, 10mbps, fail-safe rs-485/j1708 transceivers
revision number revision date description pages changed 0 10/02 initial release 1 12/05 corrected the supply current units from a to ma for the shutdown supply current vs. temperature graph in the typical operating characteristics section; updated the outputs in table 4; updated figure 15 6, 11, 17 2 11/10 added lead(pb)-free parts to the ordering information table; added the soldering temperature to the absolute maximum ratings section; updated table 4 outputs 1, 2, 11, 17 3 4/14 deleted truck and trailer applications and automotive applications from applications section 1 ? 2014 maxim integrated products, inc. 19 revision history maxim integrated cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a maxim integrated product. no circuit patent licenses are implied. maxim integrated reserves the right to change the circuitry and specifcations without notice at any time. the parametric values (min and max limits) shown in the electrical characteristics table are guaranteed. other parametric values quoted in this data sheet are provided for guidance. maxim integrated and the maxim integrated logo are trademarks of maxim integrated products, inc. max3440eCmax3444e 15kv esd-protected, 60v fault-protected, 10mbps, fail-safe rs-485/j1708 transceivers for pricing, delivery, and ordering information, please contact maxim direct at 1-888-629-4642, or visit maxim integrateds website at www.maximintegrated.com.

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