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selector guide general description the max3440e?ax3444e 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 trans- ceivers on a single bus. the devices operate from a 5v supply at data rates of up to 10mbps. true fail-safe inputs guarantee 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 ther- mal shutdown circuitry protect the driver against exces- sive power dissipation, and on-chip 15kv esd protection eliminates costly external protection devices. the max3440e?ax3444e are available in 8-pin so and pdip packages and are specified over industrial and automotive temperature ranges. applications rs-422/rs-485 communications truck and trailer applications industrial networks telecommunications systems automotive applications 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 (-40? to +125?) industry-standard pinout max3440e?ax3444e ?5kv esd-protected, ?0v fault-protected, 10mbps, fail-safe rs-485/j1708 transceivers ________________________________________________________________ maxim integrated products 1 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 pin configurations and typical operating circuits ordering information 19-2666; rev 0; 10/02 for pricing, delivery, and ordering information, please contact maxim/dallas direct! at 1-888-629-4642, or visit maxim? website at www.maxim-ic.com. part temp range pin-package max3440e esa -40 c to +85 c 8 so max3440eepa -40 c to +85 c 8 pdip max3440easa -40 c to +125 c 8 so max3440eapa -40 c to +125 c 8 pdip 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 ) ordering information continued at end of data sheet. pin configurations and typical operating circuits continued at end of data sheet.
max3440e?ax3444e ?5kv esd-protected, ?0v fault-protected, 10mbps, fail-safe rs-485/j1708 transceivers 2 _______________________________________________________________________________________ absolute maximum ratings stresses beyond those listed under ?bsolute 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 specificatio ns is not implied. exposure to absolute maximum rating conditions for extended periods may affect device reliability. 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 = +70 c) 8-pin so (derate 5.9mw/ c above +70 c)..................471mw 8-pin pdip (derate 9.09mw/ c above +70 c).............727mw operating temperature ranges max344_ee_ _ ...............................................-40 c to +85 c max344_ea_ _ .............................................-40 c to +125 c storage temperature range .............................-65 c to +150 c junction temperature ......................................................+150 c lead temperature (soldering, 10s) .................................+300 c dc electrical characteristics (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 = +25 c.) parameter symbol conditions min typ max units driver figure 1, r l = 100 ? 2v cc differential driver output v od figure 1, r l = 54 ? 1.5 v cc v 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 2v driver input low voltage v dil 0.8 v driver input current i din 2a 0 v out +12v +350 driver short-circuit output current (note 3) i osd -7v v out v cc -350 ma (v cc - 1v) v out +12v (note 3) +25 driver short-circuit foldback output current i osdf -7v v out +1v (note 3) -25 ma receiver v cc = gnd, v a, b = 12v 250 v a, b = -7v -150 a input current i a,b a, b v a, b = 60v 6ma receiver differential threshold voltage v th -7v v cm +12v -200 -50 mv receiver input hysteresis ? v th 25 mv note 1: a, b must be terminated with 54 ? or 100 ? to guarantee 60v fault protection.
max3440e?ax3444e ?5kv esd-protected, ?0v fault-protected, 10mbps, fail-safe rs-485/j1708 transceivers _______________________________________________________________________________________ 3 parameter symbol conditions min typ max units receiver logic output high voltage v oh figure 2, i oh = -1.6ma v cc - 0.6 v output low voltage v ol figure 2, i ol = 1ma 0.4 v three-state output current at receiver i ozr 0 v a, b v cc 1a receiver input resistance r in -7v v cm +12v 48 k ? receiver output short-circuit current i osr 0 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 max3440e (de/re = v cc ), max3442e (de = v cc , re = gnd), max3444e ( de = re = gnd) 30 normal operation i q no load, di = v cc or gnd max3441e (de/re = v cc ), max3443e (de = v cc , re = gnd) 10 ma de = gnd, re = v cc (max3442e/ max3443e) 20 de = gnd, re = v cc , t a = +25 c (max3442e/max3443e) 10 de = re = v cc (max3444e) 100 supply current in shutdown mode i shdn de = re = v cc , t a = +25 c (max3444e) 10 a supply current with output shorted to 60v i shrt de = gnd, re = gnd, no load output in three-state (max3443e) 15 ma dc electrical characteristics (continued) (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 = +25 c.) 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 = 0, high limit 270 450 mv receiver differential threshold f dipl v cm = 0, low limit -450 -270 mv fault-detection common-mode input voltage positive 12 v fault-detection common-mode input voltage negative -7 v protection specifications (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 = +25 c.)
max3440e?ax3444e ?5kv esd-protected, ?0v fault-protected, 10mbps, fail-safe rs-485/j1708 transceivers 4 _______________________________________________________________________________________ parameter symbol conditions min typ max units max3440e/max3442e, figure 3, r l = 54 ? , c l = 50pf driver propagation delay t plha, t plhb max3444e, r diff = 60 ? , c diff = 100pf 2000 ns 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 hl figure 4, r l = 54 ? , c l = 50pf 200 2000 ns driver output skew t s kewab , t s kewba 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 = 50p f ( m ax 3442e /m ax 3444e ) 800 ns receiver propagation delay t rplh , t rphl figure 7, c l = 20pf, v id = 2v, v cm = 0 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 recei ver d i sab l e ti m e fr om outp ut h i g ht rphz figure 8, r l = 1k ? , c l = 20pf 2000 ns receiver wake time from shutdown t rpwake figure 8, r l = 1k ? , 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 recei ver d i sab l e ti m e fr om outp ut low t rplz figure 8, r l = 1k ? , c l = 20pf 2000 ns receiver time to shutdown t shdn r l = 500 ? , c l = 50pf (max3442e/max3444e) 800 ns switching characteristics (max3440e/max3442e/max3444e) (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 = +25 c.)
max3440e?ax3444e ?5kv esd-protected, ?0v fault-protected, 10mbps, fail-safe rs-485/j1708 transceivers _______________________________________________________________________________________ 5 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 fi g ur e 6, r l = 500 ? , c l = 50p f ( m ax 3443e ) 800 ns receiver propagation delay t rplh , t rphl figure 7, c l = 20pf, v id = 2v, v cm = 0 85 ns receiver output skew t rskew c l = 20pf, t rskew = |t rplh - t rphl |15ns receiver enable time to output high t rpzh figure 8, r l = 1k ? , c l = 20pf 400 ns recei ver d i sab l e ti m e fr om outp ut h i g ht 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 recei ver d i sab l e ti m e fr om outp ut 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 switching characteristics (max3441e/max3443e) (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 = +25 c.) 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 outp ut current applies during current limiting to allow a recovery from bus contention.
max3440e?ax3444e ?5kv esd-protected, ?0v fault-protected, 10mbps, fail-safe rs-485/j1708 transceivers 6 _______________________________________________________________________________________ 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 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 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 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 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 typical operating characteristics (v cc = +5v, t a = +25 c, unless otherwise noted.) no-load supply current vs. temperature max3440e toc01 temperature ( 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 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 shutdown supply current vs. temperature max3443e toc03 temperature ( c) supply current (na) 110 95 80 65 50 35 20 5 -10 -25 0.1 1 10 0.01 -40 125 max3442e/max3443e/max3444e 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
max3440e?ax3444e ?5kv esd-protected, ?0v fault-protected, 10mbps, fail-safe rs-485/j1708 transceivers _______________________________________________________________________________________ 7 v cc d v od v oc 2 r l 2 r l di a b figure 1. driver v od and v oc r ro 0 v oh i oh (-) i ol (+) v ol v id a b figure 2. receiver v oh and v ol 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 1.5v v oh + v ol 2 v om = a b 2 figure 3. driver propagation times test circuits and waveforms 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?) di 90% 50% 1.5v 10% 90% 3v 0 2.0v t hl -2.0v a b figure 4. driver differential output delay and transition times
max3440e?ax3444e ?5kv esd-protected, ?0v fault-protected, 10mbps, fail-safe rs-485/j1708 transceivers 8 _______________________________________________________________________________________ 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 figure 6. driver enable and disable times figure 7. receiver propagation delay test circuits and waveforms (continued) 50 w generator (note 4) ? 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 = 500 w di a b de t pdzh figure 5. driver enable and disable times
max3440e?ax3444e ?5kv esd-protected, ?0v fault-protected, 10mbps, fail-safe rs-485/j1708 transceivers _______________________________________________________________________________________ 9 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 s3 = -1.5v t rpzl t rpsl 3v 0 v oh 0 1.5v re 1.5v s1 open s2 closed 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 s3 = -1.5v t rplz 3v 0 v oh 0 0.5v 1.5v ro re s1 open s2 closed s3 = 1.5v t rphz s3 r o a b ro figure 8. receiver enable and disable times test circuits and waveforms (continued) note 4: the input pulse is supplied by a generator with the following characteristics: f = 5mhz, 50% duty cycle; tr 6ns; z 0 = 50 ? . note 5: c l includes probe and stray capacitance.
max3440e?ax3444e ?5kv esd-protected, ?0v fault-protected, 10mbps, fail-safe rs-485/j1708 transceivers 10 ______________________________________________________________________________________ pin description pin max3440e max3441e max3442e max3443e max3444e name function 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 211ro receiver output. if receiver enabled and (a-b) -50mv, ro = high; if (a-b) -200mv, ro = low. 22 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. 44 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 888v cc positive supply, v cc = +4.75v to +5.25v
max3440e?ax3444e ?5kv esd-protected, ?0v fault-protected, 10mbps, fail-safe rs-485/j1708 transceivers ______________________________________________________________________________________ 11 function tables inputs outputs a-b v id differential input voltage common-mode voltage ro fault conditioned by delay fault condition 0.45v 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 -0.45v 12v and -7v 00 indeterminate x <-7v or >+12v indeterminate 1 outside common-mode voltage range table 1. max3440e/max3441e fault table x = don? care. note 1 : receiver output may oscillate with this differential input condition. transmitting inputs outputs de/re di a b 0 x high-z high-z 1001 1110 table 2. max3440e/max3441e (rs-485/rs-422) x = don? care. transmitting inputs outputs re de di a b 0 0 x high-z high-z 01001 01110 1 0 x shutdown shutdown 11001 11110 table 3. max3442e/max3443e (rs-485/rs-422) x = don? care. transmitting inputs outputs conditions txd de ab 0 1 high-z high-z 1 1 high-z high-z 0 0 1 0 dominant state 1 0 high-z high-z recessive state table 4. max3444e (j1708) application receiving inputs outputs de/re (a - b) ro 0 -0.05v 1 0 -0.2v 0 0 open/shorted 1 1 x high-z table 5. max3440e/max3441e (rs-485/rs-422) x = don? care.
detailed description the max3440e max3444e 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 output 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 circuit board is plugged into a hot back- plane (see the hot-swap capability section). the max3440e/max3442e/max3444e feature a reduced slew-rate driver that minimizes emi and reduces reflec- tions caused by improperly terminated cables, allowing error-free data transmission up to 250kbps (see the reduced 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-imped- ance state. receiver the receiver accepts a differential, rs-485/rs-422 level input (a and b), and transfers it to a single-ended, logic-level output (ro). deasserting the receiver enable places the receiver inputs (a and b) into a high-imped- ance state (see tables 1 7). 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 maxi- mum 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 standard. 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 max3440e max3444e 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 max3440e max3444e 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. max3440e?ax3444e ?5kv esd-protected, ?0v fault-protected, 10mbps, fail-safe rs-485/j1708 transceivers 12 ______________________________________________________________________________________ receiving inputs outputs re de (a - b) ro 0x -0.05v 1 0x -0.2v 0 0 x open/shorted 1 1 1 x high-z 1 0 x shutdown table 6. max3442e/max3443e (rs-485/rs-422) x = don? care. receiving inputs outputs re de (a - b) ro 0x -0.05v 1 0x -0.2v 0 0 x open/shorted 1 1 0 x high-z 1 1 x shutdown table 7. max3444e (rs-485/rs-422) function tables (continued) x = don? care.
?5kv esd protection as with all maxim devices, esd-protection structures are incorporated on all pins to protect against esd encountered during handling and assembly. the max3440e max3444e receiver inputs/driver outputs (a, b) have extra protection against static electricity found in normal operation. maxim s engineers have developed state-of-the-art structures to protect these pins against 15kv esd without damage. after an esd event, the max3440e 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 cir- cuits over the whole common-mode voltage range. the second, a thermal shutdown circuit, forces the driver out- puts into a high-impedance state if the die temperature exceeds +160 c. normal operation resumes when the die temperature cools to +140 c, resulting in a pulsed output during continuous short-circuit conditions. max3440e?ax3444e ?5kv esd-protected, ?0v fault-protected, 10mbps, fail-safe rs-485/j1708 transceivers ______________________________________________________________________________________ 13 charge-current- limit resistor discharge resistance storage capacitor c s 100pf r c 1m w r d 1.5k w high- voltage dc source device under test 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 figure 9b. human body model current waveform
max3440e?ax3444e ?5kv esd-protected, ?0v fault-protected, 10mbps, fail-safe rs-485/j1708 transceivers 14 ______________________________________________________________________________________ hot-swap capability hot-swap inputs inserting circuit boards into a hot, or powered, back- plane 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 max3440e max3444e enable inputs to a defined logic level. meanwhile, leak- age currents of up to 10a from the high-impedance out- put, or capacitively coupled noise from v cc or gnd, could cause an input to drift to an incorrect logic state. to prevent such a condition from occurring, the max3440e max3443e feature hot-swap input circuitry on de, de/re, and re to guard against unwanted dri- ver activation during hot-swap situations. 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 cur- rent 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 current sink, and m1, a 100a current sink, pull de to gnd through a 5.6k ? resistor. m2 pulls de to the disabled state against an external parasitic capaci- tance up to 100pf that may drive de high. after 15s, the timer deactivates 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 standard, 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 max3440e max3444e transceivers 1/4-unit-load receiver input impedance (48k ? ) allows up to 128 transceivers connected in parallel on one communica- tion 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 reflections the max3440e/max3442e/max3444e are slew-rate limited, minimizing emi and reducing reflections caused by improperly terminated cables. figure 11 shows the driver output waveform and its fourier analy- sis of a 125khz signal transmitted by a max3443e. high-frequency harmonic components with large ampli- tudes are evident. figure 12 shows the same signal displayed for a max3442e transmitting under the same conditions. figure 12 s high-frequency harmonic components are much lower in amplitude, compared with figure 11 s, and the potential for emi is significantly reduced. v cc timer timer de (hot swap) 15 s 100 a m1 m2 5.6k ? 2ma figure 10. simplified structure of the driver enable pin (de)
in general, a transmitter s rise time relates directly to the length of an unterminated stub, which can be dri- ven 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 transmitter s rise time. for example, the max3442e s rise time is typically 800ns, which results in excellent waveforms with a stub length up to 53ft. a system can work well with longer unterminated stubs, even with severe reflections, if the waveform settles out before the uart samples them. rs-485 applications the max3440e max3443e transceivers provide bidi- rectional data communications on multipoint bus trans- mission 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 recessive state. c1 and c2 combine to form a 6mhz lowpass filter, effec- tive 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 pseudotermination. this makes the implementation more flexible, as no specific termination nodes are required at the ends of the bus. max3440e?ax3444e ?5kv esd-protected, ?0v fault-protected, 10mbps, fail-safe rs-485/j1708 transceivers ______________________________________________________________________________________ 15 5.00mhz 500khz/div 0 20db/div 2v/div figure 11. driver output waveform and fft plot of max3443e transmitting a 125khz signal 5.00mhz 500khz/div 0 20db/div 2v/div figure 12. driver output waveform and fft plot of max3442e transmitting a 125khz signal
max3440e?ax3444e ?5kv esd-protected, ?0v fault-protected, 10mbps, fail-safe rs-485/j1708 transceivers 16 ______________________________________________________________________________________ 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 bb b a a a 120 ? 120 ? d r max3440e max3441e fault fault fault 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 bb b a a a 120 ? 120 ? d r max3442e max3443e re re re figure 14. max3442e/max3443e typical rs-485 network
max3440e?ax3444e ?5kv esd-protected, ?0v fault-protected, 10mbps, fail-safe rs-485/j1708 transceivers ______________________________________________________________________________________ 17 r1 4.7k ? r3 47 ? c1 2.2nf c2 2.2nf r2 4.7k ? ro rx tx r4 47 ? j1708 bus b a v cc txd d r de re max3444e figure 15. j1708 application circuit chip information transistor count: 310 process: bicmos 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 pin configurations and typical operating circuits (continued) 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
max3440e?ax3444e ?5kv esd-protected, ?0v fault-protected, 10mbps, fail-safe rs-485/j1708 transceivers 18 ______________________________________________________________________________________ ordering information (continued) part temp range pin-package max3441e esa -40 c to +85 c 8 so max3441eepa -40 c to +85 c 8 pdip MAX3441EASA -40 c to +125 c 8 so max3441eapa -40 c to +125 c 8 pdip max3442e esa -40 c to +85 c 8 so max3442eepa -40 c to +85 c 8 pdip max3442easa -40 c to +125 c 8 so max3442eapa -40 c to +125 c 8 pdip max3443e csa 0 c to +70 c 8 so max3443ecpa 0 c to +70 c 8 pdip max3443eesa -40 c to +85 c 8 so max3443eepa -40 c to +85 c 8 pdip max3443easa -40 c to +125 c 8 so max3443eapa -40 c to +125 c 8 pdip max3444e esa -40 c to +85 c 8 so max3444eepa -40 c to +85 c 8 pdip max3444easa -40 c to +125 c 8 so max3444eapa -40 c to +125 c 8 pdip
max3440e?ax3444e ?5kv esd-protected, ?0v fault-protected, 10mbps, fail-safe rs-485/j1708 transceivers ______________________________________________________________________________________ 19 package information (the package drawing(s) in this data sheet may not reflect the most current specifications. for the latest package outline info rmation, go to www.maxim-ic.com/packages .) soicn .eps package outline, .150" soic 1 1 21-0041 b rev. document control no. approval proprietary information title: top view front view max 0.010 0.069 0.019 0.157 0.010 inches 0.150 0.007 e c dim 0.014 0.004 b a1 min 0.053 a 0.19 3.80 4.00 0.25 millimeters 0.10 0.35 1.35 min 0.49 0.25 max 1.75 0.050 0.016 l 0.40 1.27 0.394 0.386 d d min dim d inches max 9.80 10.00 millimeters min max 16 ac 0.337 0.344 ab 8.75 8.55 14 0.189 0.197 aa 5.00 4.80 8 n ms012 n side view h 0.244 0.228 5.80 6.20 e 0.050 bsc 1.27 bsc c h e e b a1 a d 0-8 l 1 variations:
max3440e?ax3444e ?5kv esd-protected, ?0v fault-protected, 10mbps, fail-safe rs-485/j1708 transceivers maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a maxim product. no circu it patent licenses are implied. maxim reserves the right to change the circuitry and specifications without notice at any time. 20 ____________________maxim integrated products, 120 san gabriel drive, sunnyvale, ca 94086 408-737-7600 ? 2002 maxim integrated products printed usa is a registered trademark of maxim integrated products. pdipn.eps package information (continued) (the package drawing(s) in this data sheet may not reflect the most current specifications. for the latest package outline info rmation, go to www.maxim-ic.com/packages .)

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