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1 for more information www.linear.com/ltc2876 typical a pplica t ion fea t ures descrip t ion 60v rugged profibus rs485 transceivers the lt c ? 2876 and ltc2877 are profibus rs485 transceivers designed to meet the test specifications for profibus-dp masters and profibus-dp slaves, fully compatible with iec 61158-2, type 3: medium attachment unit ( mau). with operation up to 20 mbps, the ltc2876/ ltc2877 supports all profibus data rates up to 12mbps. the ltc2876 and ltc2877 are exceptionally robust, toler - ating 60 v faults on the bus pins and protected to 52 kv esd. these devices are suitable for harsh environments or where 24 v power might be inadvertently connected. extended 25 v input common mode range and full fail - safe operation improve data communication reliability in noisy systems. the ltc2876 and ltc2877 meet profibus and rs485 specifications with a supply voltage of 4.5 v to 5.5 v but can operate down to 3v with reduced supply current. product selection guide part number logic supply pin package ltc2876 no dfn-8, msop-8 ltc2877 yes dfn-10, msop-10 a pplica t ions n profibus iec 61158-2 compliant n protected from overvoltage line faults to 60v n 52kv esd interface pins, 15kv all other pins n 2kv (level 4) iec61000-4-4 fast transient burst n 25v working common mode range n 20mbps maximum baud rate n 1.65v to 5.5v logic supply pin for flexible digital interfacing (ltc2877) n 5v supply can operate down to 3v for low power, low swing applications n fully balanced differential receiver thresholds with 240mv hysteresis for superior noise tolerance and low duty cycle distortion n receiver failsafe for open, shorted and terminated conditions n wide operating temperature range: C40c to 125c n available in small dfn and msop packages n profibus-dp n industrial communication networks n rs485 and rs422 systems n 3v low voltage differential signaling l, lt , lt c , lt m , linear technology and the linear logo are registered trademarks of linear technology corporation. all other trademarks are the property of their respective owners. z o = 150 eye diagram of 12mbps signal at the near and far end of a 100m profibus cable driven by the ltc2877 using 2 8 C1 prbs pattern 20ns/div pb?pa 2v/div b? a 2v/div 28767 ta01b near end far end ltc 2876/ ltc 2877 28767fa pa pb 0.1f ltc2877 sensor 390 pb pa 390 220 1.8v 5v 5v profibus cable c 1f 390 390 220 b a v cc 28767 ta01a v l gnd di re ro de
2 for more information www.linear.com/ltc2876 a bsolu t e maxi m u m r a t ings supply voltages (v cc , v l ) ............................ C0. 3 v to 6v logic input voltages ( re , de , di ) ................ C 0.3 v to 6v line interface i/o ( pa , pb) .......................... C 60 v to 60 v line interface i/o difference (pbC pa ) ..... C12 0 v to 120 v receiver output ( ro ) ltc 287 6 ...................................... C 0.3 v to v cc + 0.3 v ltc 287 7 ....................................... C 0.3 v to v l + 0.3 v (notes 1, 2) operating ambient temperature range ( note 3) ltc 287 xc ................................................ 0 c to 70 c ltc 287 x i .............................................. C 40 c to 85 c ltc 287 xh .......................................... C 40 c to 125 c storage temperature range .................. C 65 c to 150 c lead temperature ( soldering , 10 sec ).................... 300 c ltc2876 ltc2876 top view dd package 8-lead (3mm 3mm) plastic dfn 5 6 7 8 9 gnd 4 3 2 1ro re de di v cc pa pb gnd t jmax = 150c, ja = 43c/w, jc = 5.5c/w exposed pad ( pin 9) is gnd, must be soldered to pcb 1 2 3 4 ro re de di 8 7 6 5 v cc pa pb gnd top view 9 gnd ms8e package 8-lead plastic msop t jmax = 150c, ja = 40c/w, jc = 10c/w exposed pad ( pin 9) is gnd, must be soldered to pcb ltc2877 ltc2877 top view 11 gnd dd package 10-lead (3mm 3mm) plastic dfn 10 9 6 7 8 4 5 3 2 1 v cc pa pb nc gnd ro re de di v l t jmax = 150c, ja = 43c/w, jc = 5.5c/w exposed pad ( pin 11) is gnd, must be soldered to pcb 1 2 3 4 5 ro re de di v l 10 9 8 7 6 v cc pa pb nc gnd top view 11 gnd mse package 10-lead plastic msop t jmax = 150c, ja = 40c/w, jc = 10c/w exposed pad ( pin 11) is gnd, must be soldered to pcb p in c on f igura t ion ltc 2876/ ltc 2877 28767fa
3 for more information www.linear.com/ltc2876 o r d er i n f or m a t ion e lec t rical c harac t eris t ics the l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at t a = 25c. v cc = v l = 5v unless otherwise noted. lead free finish tube tape and reel part marking package description temperature range ltc2876cms8e#pbf ltc2876ims8e#pbf ltc2876hms8e#pbf ltc 2876cms8e#trpbf ltc2876ims8e#trpbf ltc2876hms8e#trpbf ltgtn l tgtn ltgtn 8-lead plastic msop 8-lead plastic msop 8-lead plastic msop 0c to 70c C40c to 85c C40c to 125c ltc2876cdd#pbf ltc2876idd#pbf ltc2876hdd#pbf ltc 2876cdd#trpbf ltc2876idd#trpbf ltc2876hdd#trpbf lgtm lgtm lgtm 8-lead plastic dfn 8-lead plastic dfn 8-lead plastic dfn 0c to 70c C40c to 85c C40c to 125c ltc2877cmse#pbf ltc2877imse#pbf ltc2877hmse#pbf ltc 2877cmse#trpbf ltc2877imse#trpbf ltc2877hmse#trpbf ltgtq l tgtq ltgtq 10-lead plastic msop 10-lead plastic msop 10-lead plastic msop 0c to 70c C40c to 85c C40c to 125c ltc2877cdd#pbf ltc2877idd#pbf ltc2877hdd#pbf ltc 2877cdd#trpbf ltc2877idd#trpbf ltc2877hdd#trpbf lgtp lgtp lgtp 10-lead plastic dfn 10-lead plastic dfn 10-lead plastic dfn 0c to 70c C40c to 85c C40c to 125c consult lt c marketing for parts specified with wider operating temperature ranges. consult lt c marketing for information on nonstandard lead based finish parts. for more information on lead free part marking, go to: http://www.linear.com/leadfree/ for more information on tape and reel specifications, go to: http://www.linear.com/tapeandreel/. some packages are available in 500 unit reels through designated sales channels with #trmpbf suffix. symbol parameter conditions min typ max units supplies v cc primary power supply profibus, rs485 l 4.5 5.5 v low voltage rs485 (note 6) l 3.0 v v l logic interface power supply ltc2877 only l 1.65 v cc v i ccs ltc2876 supply current in shutdown mode de = 0v, re = v cc , di = v cc l 0 5 a de = 0v, re = v cc , di = 0v l 12 25 a ltc2877 supply current in shutdown mode de = 0v, re = v l = v cc , di = 0v or v l l 0 5 a i ccr supply current with only receiver enabled no load, de = 0v, re = 0v l 600 900 a i ccd supply current with only driver enabled no load, de = re = v cc = v l l 700 1100 a i ccdr supply current with both driver and receiver enabled no load, de = v cc = v l , re = 0v l 750 1200 a ltc2877 logic supply current in shutdown mode de = 0v, re = v l , di = v l l 0 5 a de = 0v, re = v l , di = 0v l 12 25 a ltc2877 logic supply current with both driver and receiver enabled de = v l , re = 0v, di = v l l 30 60 a de = v l , re = 0v, di = 0v l 65 120 a http://www .linear.com/product/ltc2876#orderinfo ltc 2876/ ltc 2877 28767fa
4 for more information www.linear.com/ltc2876 e lec t rical c harac t eris t ics the l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at t a = 25c. v cc = v l = 5v unless otherwise noted. symbol parameter conditions min typ max units driver v od(pp) differential bus output voltage (bCa) with profibus load profibus load (figure 1) r cable = 0, v cc = 4.5v to 5.5v r cable = 5.5, v cc = 4.5v to 5.5v r cable = 11, v cc = 4.75v to 5.5v l l l 4 4 4 7 7 7 v p-p(diff) v p-p(diff) v p-p(diff) v bpp-app single-ended bus output amplitude difference (b pp C a pp ) all of the conditions above l 0.5 v v bpp+app single-ended bus output amplitude sum |b pp + a pp | all of the conditions above l 4 v |v od(485) | rs485 differential driver output voltage, in either logic state figure 2 with no load l v cc v r l = 27,v cc = 4.5v to 5.5v (figure 2) l 1.5 3.4 v r l = 27,v cc = 3.0v to 3.6v (figure 2) l 0.8 1.8 v |v od(422) | rs422 differential driver output voltage, either logic state figure 2 with no load l v cc v r l = 50,v cc = 4.5v to 5.5v (figure 2) l 2 4 v r l = 50,v cc = 3.0v to 3.6v (figure 2) l 1 2 v |v od(485) |, |v od(422) | rs485, rs422 change in magnitude of driver differential output voltage r l = 27 (rs485) or r l = 50 (rs422) (figure 2) l 0.2 v v oc(485) , v oc(422) rs485, rs422 driver common-mode output voltage r l = 27 (rs485) or r l = 50 (rs422) (figure 2) l 3 v |v oc(485) |, |v oc(422) | rs485, rs422 change in magnitude of driver common-mode output voltage r l = 27 (rs485) or r l = 50 (rs422) (figure 2) l 0.2 v i osd maximum driver short-circuit current C60v (pb or pa ) 60v (figure 3) l 150 250 ma receiver i in input current (pa , pb) v cc = 0v or 5v, v bus = 12v (figure 4) v cc = 0v or 5v, v bus = C7v (figure 4) l l C100 160 a a r in input resistance v bus = C25v or 25v (figure 4) l 75 112 135 k v cm common mode input voltage (pa + pb)/2 for data reception l 25 v v ts + differential input signal threshold voltage (pbC pa ) rising C25v v cm 25v, edge rates > 100mv/s (note 5) (figure 13) l 50 120 200 mv v ts C differential input signal threshold voltage (pbC pa ) falling C25v v cm 25v, edge rates > 100mv/s (note 5) (figure 13) l C50 C120 C200 mv v ts differential input signal hysteresis edge rates > 100mv/s (note 5) (figure 13) 240 mv v tfs + differential input failsafe threshold voltage (pbC pa ) rising C25v v cm 25v, dc bus voltages (figure 13) l C20 C75 C200 mv v tfs C differential input failsafe threshold voltage (pbC pa ) falling C25v v cm 25v, dc bus voltages (figure 13) l C50 C120 C200 mv v tfs differential input failsafe hysteresis dc bus voltages (figure 13) 45 mv v oh receiver output high voltage v cc 4.5v, i(ro) = C3ma (ltc2876) v l 2.25v, i(ro) = C3ma (ltc2877) v l < 2.25v, i(ro) = C2ma (ltc2877) l l l v cc C 0.4v v l C 0.4v v l C 0.4v v v v v ol receiver output low voltage v l 1.65v, i(ro) = 3ma (ltc2877) v cc 3.0v, i(ro) = 3ma (ltc2876) l l 0.4 0.4 v v receiver three-state (high impedance) output current on ro re = high, ro = 0v l C20 C40 a receiver three-state (high impedance) output current on ro re = high, ro = v cc (ltc2876) or v l (ltc2877) l 0 5 a ltc 2876/ ltc 2877 28767fa
5 for more information www.linear.com/ltc2876 e lec t rical c harac t eris t ics the l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at t a = 25c. v cc = v l = 5v unless otherwise noted. symbol parameter conditions min typ max units receiver short-circuit current re = low, ro = 0v or v cc (ltc2876) or v l (ltc2877) l 12 20 ma logic low level input voltage (de, di, re ) ltc2876, 3.0 v cc 5.5v l 0.25 ? v cc v ltc2877, 1.65 v l 5.5v l 0.25 ? v l v high level input voltage (de, di, re ) ltc2876, 3.0 v cc 5.5v l 0.75 ? v cc v ltc2877, 1.65 v l 5.5v l 0.75 ? v l v logic input current low (de) de = 0v l 0 C5 a logic input current low (di, re ) di or re = 0v l C3 C10 C20 a logic input current high (de) de = v cc (ltc2876) or v l (ltc2877) l 3 10 20 a logic input current high (di, re ) (di, re) = v cc (ltc2876) or v l (ltc2877) l 0 5 a esd (note 4) esd protection level of interface pins (pa , pb) human body model to gnd or v cc , or v l , powered or unpowered 26 kv human body model to gnd, unpowered 52 kv esd protection level of all other pins (de, di, re, v cc , v l ) human body model 15 kv symbol parameter conditions min typ max units f max maximum data rate (note 4) l 20 mbps driver t plhd , t phld driver input to output v cc = 3.3v or 5v (figure 5) l 13 50 ns t pd driver input to output difference |t plhd C t phld | (figure 5) l 2 9 ns t skewd driver output pb to output pa (figure 5) l 9 ns t rd , t fd driver rise or fall time v cc = 3.3v or 5v (figure 5) l 4 15 ns t zld , t zhd , t lzd , t hzd driver enable or disable time re = 0v (figure 6) l 180 ns t zhsd , t zlsd driver enable from shutdown re = high (figure 6) l 15 s t shdnd time to shutdown with de re = high (figure 6) l 180 ns receiver t plhr , t phlr receiver input to output v cm = 2.25v, (pbCpa ) = 1.5v, t r and t f < 4ns, v cc = 3.3v or 5v (figure 7) l 50 70 ns t pr receiver input to output difference |t plhr C t phlr | (figure 7) l 2 14 ns t rr , t fr receiver output rise or fall time (figure 7) l 3 15 ns t zlr , t zhr , t lzr , t hzr receiver enable/disable time de = high (figure 8) l 40 ns t zhsr , t zlsr receiver enable from shutdown de = 0v, (figure 9) l 9 s t shdnr time to shutdown with re de = 0v, (figure 9) l 40 ns s wi t ching c harac t eris t ics the l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at t a = 25c. v cc = v l = 5v unless otherwise noted. ltc 2876/ ltc 2877 28767fa
6 for more information www.linear.com/ltc2876 e lec t rical c harac t eris t ics note 1: stresses beyond those listed under absolute maximum ratings may cause permanent damage to the device. exposure to any absolute maximum rating condition for extended periods may affect device reliability and lifetime. note 2: all currents into device pins are positive; all currents out of device pins are negative. all voltages are referenced to device ground unless otherwise specified. note 3: this ic includes overtemperature protection that is intended to protect the device during momentary overload conditions. junction temperature exceeds 150c when overtemperature protection is active. continuous operation above the specified maximum operating temperature may result in device degradation or failure. note 4: not tested in production. note 5: the dependency on edge rate is tested indirectly. note 6: does not meet rs485 or profibus specifications. see the applications information section for more information about running with a 3v supply. ltc 2876/ ltc 2877 28767fa
7 for more information www.linear.com/ltc2876 typical p er f or m ance c harac t eris t ics v l supply current vs data rate driver differential output voltage vs supply voltage driver differential output voltage vs temperature driver output low/high voltage vs output current driver output short-circuit current vs voltage driver and receiver propagation delay vs v cc v cc supply current vs voltage for various modes, no load v cc supply current vs temperature for various modes, no load v cc supply current vs data rate t a = 25c. v cc = v l = 5v, unless otherwise noted. (note 2) ltc 2876/ ltc 2877 28767fa 4.5 4 4.5 5 5.5 0 1 2 3 4 5 5 6 7 v od (v) 28767 g05 v od(pp) profi load (fig. 1), v cc = 5v v od(422) (fig. 2, r l = 50), v cc = 5v v od(485) (fig. 2, r l = 27), v cc = 5v v od(422) (fig. 2, r l = 50), v cc = 3.3v v od(485) (fig. 2, r l = 27), v cc = 3.3v temperature (c) 5.5 ?50 ?25 0 25 50 75 100 125 150 0 500 1 2 3 4 5 6 v od (v) 28767 g06 v oh (v cc = 5.0v) v oh (v cc = 3.3v) 550 v ol (v cc = 5.0v) v ol (v cc = 3.3v) output current (ma) 0 10 20 30 40 50 0 600 1 2 3 4 5 driver output voltage (v) 28767 g07 output low output high output voltage (v) 650 ?60 ?40 ?20 0 20 40 60 ?160 ?120 ?80 700 ?40 0 40 80 120 160 output current (ma) 28767 g08 driver receiver 750 v cc 3 3.5 4 4.5 5 5.5 0 10 20 0 30 40 50 60 propagation delay (ns) 28767 g09 i ccdr 1 2 3 4 5 v cc supply current (a) i ccs (na) 28767 g01 i ccdr i ccd i ccd i ccr i ccs (na) temperature (c) ?50 ?25 0 25 50 75 100 i ccr 125 150 500 575 650 725 800 0.1 1 10 i ccs (na) 100 1k 10k i ccdr , i ccd , i ccr (a) i ccs (na) 28767 g02 rs485 54/100pf load (fig. 5) v cc = 5v profi 100m cable w/term (fig.1) v cc = 5v rs485 54/100pf load (fig. 5) v cc = 3.3v no load, v cc = 5v v cc supply voltage (v) no load, v cc = 3.3v data rate (mbps) 0 5 10 15 20 0 10 20 3 30 40 50 v cc supply current (ma) 28767 g03 v l = 5v, c ro = 15pf v l = 5v, c ro = 0pf v l = 1.65v, c ro = 15pf v l = 1.65v, c ro = 0pf data rate (mbps) 3.5 0 5 10 15 20 0 0.5 1.0 1.5 2.0 4 2.5 3.0 v l supply current (ma) 28767 g04 v od(pp) profibus loads (fig. 1) v od(422) (fig. 2, r l = 50) v od(485) (fig. 2, r l = 27) v cc (v) 3 3.5
8 for more information www.linear.com/ltc2876 typical p er f or m ance c harac t eris t ics receiver propagation delay vs temperature receiver propagation delay difference vs temperature receiver output voltage vs output current (source and sink) receiver output voltage vs v l voltage (ltc2877) profibus operation at 12mbps v cc = 5v rs485 operation at 20mbps v cc = 3.3v driver propagation delay vs temperature driver output skew vs temperature driver output propagation delay difference vs temperature t a = 25c. v cc = v l = 5v, unless otherwise noted. (note 2) output current (absolute value, ma) 0 0 receiver output voltage (v) 3 2 1 4 5 6 2 4 6 28767 g15 8 v l = 5.5v v l = 3.3v v l = 2.25v v l = 1.65v v l = 1.65v to 5.5v ltc 2876/ ltc 2877 28767fa 75 ?25 0 25 50 75 100 125 150 ?5 ?4 100 ?3 ?2 ?1 0 1 2 3 4 5 ?t pr (ns) 125 28767 g14 v ol for i(ro) = +2ma v l ?v oh for i(ro) = ?2ma v ol for i(ro) = +3ma v l ?v oh for i(ro) = ?3ma v l (v) 1.5 2.5 3.5 4.5 150 5.5 0 100 200 300 400 v ol or v oh (mv) 28767 g16 r cable = 0 (fig. 1) double profibus termination 0 50ns/div di 5v/div pa 1v/div pb 1v/div 28767 g17 r ldiff = 54; c l =100pf (fig. 5) 20ns/div 3 di 2v/div pa 0.5v/div pb 0.5v/div 28767 g18 6 9 12 15 v cc = 3.3v 18 21 24 27 30 propagation delay (ns) 28767 g10 v cc = 3.3v v cc = 5v temperature (c) v cc = 5v ?50 ?25 0 25 50 75 100 125 150 ?5 temperature (c) ?4 ?3 ?2 ?1 0 1 2 3 4 5 ?50 t skewd (ns) 28767 g11 v cc = 3.3v v cc = 5v temperature (c) ?50 ?25 0 25 50 ?25 75 100 125 150 ?5 ?4 ?3 ?2 ?1 0 0 1 2 3 4 5 ?t pd (ns) 28767 g12 v cc = 3.3v v cc = 5v temperature (c) 25 ?50 ?25 0 25 50 75 100 125 150 40 50 45 50 55 60 propagation delay (ns) 28767 g13 v cc = 3.3v v cc = 5v temperature (c) ?50
9 for more information www.linear.com/ltc2876 p in func t ions ro (pin 1): receiver output. supplied by v cc in the ltc2876 or v l in the ltc2877. if the receiver is enabled (re low) and pbCpa > 200 mv, then ro will be high. if pbC pa < C200 mv, then ro will be low. if the receiver inputs are open, shorted, or terminated without being driven for more than about 1.5s, ro will be high. integrated 250k pull-up resistor to supply. re ( pin 2): receiver enable. logic levels defined by the v cc supply in the ltc2876 or the v l supply in the ltc2877. a low input enables the receiver. a high input forces the receiver output into a high impedance state. if re is high with de low, the device enters a low power shutdown state. integrated 500k pull-up resistor to supply. de (pin 3): driver enable. logic levels defined by the v cc supply in the ltc2876 or the v l supply in the ltc2877. a high input on de enables the driver. a low input forces the driver outputs into a high impedance state. if de is low with re high, the device enters a low power shutdown state. integrated 500k pull-down resistor to ground. di ( pin 4): driver input. logic levels defined by the v cc supply in the ltc2876 or the v l supply in the ltc2877. if the driver outputs are enabled ( de high), then a low on di drives a negative differential voltage between pb and pa . a high on di, with the driver outputs enabled, drives a positive differential voltage between pb and pa . integrated 500k pull-up resistor to supply. v l (na/pin 5): logic supply: 1.65v v l v cc . powers ro, re , de, and di on ltc2877 only. bypass with 0.1f ceramic capacitor to gnd. gnd (pin 5, 9/pin 6,11): ground nc (na/pin 7): not internally connected. pb (pin 6/pin 8): profibus b. non-inverting receiver input and non-inverting driver output. connect this to the b wire ( positive) in a profibus network. in most non-profibus applications, this should connect to the a terminal. see the applications information section for more information on a vs b naming conventions. pa (pin 7/pin 9): profibus a. inverting receiver input and inverting driver output. connect this to the a wire ( negative) in a profibus network. in most non- profibus applications, this should connect to the b terminal. see the applications information section for more information on a vs b naming conventions. v cc (pin 8/pin 10): power supply . 4.5v v cc 5.5 v for profibus and rs485 compliant applications ; 3.0v v cc 5.5 v for a wide range of usage. see 3.3 v operation in the applications information section for details. bypass with 1f ceramic capacitor to gnd. exposed pad ( pin 9/pin 11): must be connected to gnd. (ltc2876/ltc2877) ltc 2876/ ltc 2877 28767fa
10 for more information www.linear.com/ltc2876 b lock diagra m ltc 2876/ ltc 2877 28767fa v cc v cc gnd re ro de 3v to 5.5v v cc v cc v cc ltc2876 1.65v to v cc mode control v cc 3v to 5.5v gnd driver receiver pa pb mode control v l driver receiver pa pb 28767 bd2 28767 bd1 v cc di re ro de ltc2877 di
11 for more information www.linear.com/ltc2876 tes t c ircui t s + ? + ? figure 1. driver differential output voltages for profibus load figure 2. driver output voltages in rs485 and rs422 configurations + ? figure 3. drive output short-circuit current ltc 2876/ ltc 2877 28767fa v bpp?app = |b pp ? a pp | v bpp+app = b pp + a pp measurements taken at steady state 28767 f01 v cc di re ro de pa 0 pb high high ltc2876/ltc2877 390 390 220 r cable r cable b b a v cc 390 390 220 v cc pb pa cm 0 a pb?pa v od(485) + ?|v oc(485) | v od(485) ? measurements taken at steady state for rs422 measurements, substitute 485 with 422 in this figure. v od(485) = pb?pa ? |v od(485) | = |v od(485) + ? v od(485) ? | 28767 f02 b? a v cc di re ro de pa pb high high ltc2876/ltc2877 0 cm v od(485) r l r l v oc(485) 28767 f03 v cc di re b pp ro de high high or low high ltc2876/ltc2877 i osd pa pb ?60v to +60v v od(pp) a pp
12 for more information www.linear.com/ltc2876 tes t c ircui t s + ? figure 4. receiver input current and input resistance figure 5. driver timing measurement ltc 2876/ ltc 2877 28767fa de low low high or low ltc2876/ltc2877 i in pa pb v bus 28767 f05 r in = di pa 0v v cc * v o ?v o 90% 90% 0 0 v bus i in 10% 10% pb pb?pa t plhd t phld t skewd t rd t fd *for the ltc2877, substitute v l for v cc 28767 f04 v cc di re ro de high high ltc2876/ltc2877 pa 54 100pf pb 100pf v cc di re ro
13 for more information www.linear.com/ltc2876 figure 6. driver enable, disable and shutdown timing measurements tes t c ircui t s figure 7. receiver propagation delay measurements ltc 2876/ ltc 2877 28767fa ?v cc v cc v ol v oh pb or pa t zld , t zlsd t zhd , t zhsd t lzd 0.5v 0.5v 28767 f06 t hzd , t shdnd *for the ltc2877, substitute v l for v cc v cc di re ro de pa pb de low or high low or high ltc2876/ltc2877 500 50pf v cc when di low gnd when di high gnd when di low v cc when di high 500 50pf 28767 f07 pa or pb low low low pb?pa ro 1.5v ?1.5v v cc * 0 90% 0v 90% 10% 10% 0v t plhr ?t pr = |t plhr ? t phlr | t phlr t rr *for the ltc2877, substitute v l for v cc t fr 0v ?v cc * ?v cc * v cc di re ro de ltc2876/ltc2877 15pf v cc * pa pb (pb?pa)/2 (pb?pa)/2 v cm ?v cc * ?v cc
14 for more information www.linear.com/ltc2876 figure 8. receiver enable and disable timing measurements figure 9. receiver shutdown timing measurements tes t c ircui t s ltc 2876/ ltc 2877 28767fa v cc v ol v oh ro t zlr t zhr t lzr 0.5v 0.5v t hzr 28767 f08 ?v cc * *for the ltc2877, substitute v l for v cc v cc di re ro de high low or high re ltc2876/ltc2877 15pf 1k v cc for di low gnd for di high pa pb 28767 f09 re ro 0v ro 0v v cc * ?v cc * ?v cc * v cc * v ol v oh ro t zlsr t zhsr 0v t shdnr 0.5v 0.5v *for the ltc2877, substitute v l for v cc t shdnr ?v cc * v cc di re 0v ro de low low ltc2876/ltc2877 15pf 1k v cc for case1 gnd for case2 case 1 pa v cc * pb 0v v cc case 2 v cc 0v ?v cc * ?v cc *
15 for more information www.linear.com/ltc2876 note: specifications in this section represent typical values unless otherwise noted. profibus-dp and rs485 profibus-dp can communicate over a variety of media, including copper wires, fiber optics, and even air in an infrared communicator. by far, the most commonly used media is a twisted pair of wires connecting devices that communicate with tia/eia-485-a (rs485) transceivers. rs485 offers high speed differential signaling that is robust for communication between multiple devices over long distances in noisy environments such as factory applications. not all rs485 transceivers are suitable for profibus although the profibus standard specifies the use of rs485 devices at the physical layer, there are differences in the cable, termination, and driver requirements from rs485. a device meeting rs485 specifications may not a pplica t ions i n f or m a t ion be compliant to profibus requirements. the ltc2876/ ltc2877 was designed specifically to meet profibus and rs485 requirements and is tested in a way that ensures this. cable and termination differences from rs485 the cable and termination network used for profibus is different than for rs485 as illustrated in figure 10. the profibus network includes bus biasing resistors that are used in conjunction with the differential termination resistors on each end of the bus. the cable is a shielded twisted pair with an impedance of 150. oddly enough, the effective differential resistance of the specified termina - tion network is 172, which is not a perfect match for the 150 cable, resulting in a slightly underdamped network. this manifests itself as a small bump, or increase in the signal voltage, at the receiving end of the cable, lasting twice as long as the cable propagation delay. in contrast, the rs485 network shows the preferred configuration with only differential termination resistors at each end of the bus, matching the 120 characteristic impedance of the cable. figure 10. cable and termination differences in rs485 and profibus multi-node networks. profibus type a cable and termination shown in profibus example ( top ) ltc 2876/ ltc 2877 28767fa profibus master profibus station profibus station profibus station 5v 390 220 390 120 rs485 master rs485 node rs485 node rs485 node 120 28767 f10 pro?bus multi-node network twisted pair cable (z o = 150) rs485 multi-node network twisted pair cable (z o = 120) 5v 390 220 390
16 for more information www.linear.com/ltc2876 a pplica t ions i n f or m a t ion driver output requirement differences from rs485 the driver requirements for profibus are specified dif- ferently than how the rs485 standard specifies them. a key difference is the terminated driver output voltage, v od , as described below. the profibus driver output levels are required to meet the following condition as stated in the test specification for profibus dp masters and test specification for profibus dp slaves: ? the differential voltage between a- and b-line shall be a minimum of 4 v and a maximum of 7 v, peak-to-peak differential. ? this measurement shall be taken at the far end of the cable in use, with termination at each end. on the other hand, rs485 specifies the following: ? the differential voltage between a- and b-line shall be a minimum of 1.5 v and a maximum of 5 v, peak dif - ferential. ? this measurement shall be taken at the driver terminals with a 54 resistor between a and b. clearly, these requirements are quite different. a common misunderstanding is that if an rs485 driver develops more than 2.1 v across a 54 rs485 resistive load, then it will meet profibus requirements when used with a pro - fibus termination network. this is not always the case . furthermore, the strength of the driver can be too high, exceeding the upper limit of the profibus specification (7v p-p ). the best way to ensure profibus compliance is to test the device with a profibus load. the ltc2876 and ltc2877 are tested with a profibus load and with extra resistance added to represent cable losses for 100 m and 200 m to ensure they meet the profibus v od requirement. the devices are also fully tested with rs485 loads to ensure they meet rs485 specifications. see the electrical characteristics section for details. d river o pera tion the driver is enabled when the ltc2876/ltc2877 is powered up, de is high, and there are no thermal faults. the polarity of pbC pa follows that of di. that is, when di is high, pb drives to a voltage that is greater than pa . if di is low, pa is higher than pb. when the driver is disabled with de low, both outputs are high impedance and the overall pin resistance is dominated by the receiver inputs sharing pins pa and pb. d river o ver voltage and o vercurrent p rotection the driver outputs pa and pb are protected from short circuits to any voltage within the absolute maximum range of C60 v to +60 v, with a maximum differential voltage of C120 v to +120 v. the maximum short-circuit current to any voltage within this range is 250 ma. the driver includes a progressive foldback current limiting circuit that continuously reduces the driver current limit with increasing output short circuit voltage to better manage power dissipation and heating effects. the ltc2876/ltc2877 also features thermal shutdown protection that disables the driver and receiver in case of excessive power dissipation (see note 3). r eceiver the receiver provides full profibus and rs485 compat - ibility. when enabled, the state of ro reflects the polarity of (pbCpa ). when the receiver is disabled, the output is high impedance and ro weakly pulled high through an internal 250k pull-up resistor. high receiver input resistance permits 200 nodes the rs485 and profibus specifications allows for up to 32 receivers, each contributing one unit load, to be con - nected together in one network. the input resistance of the ltc2876/ltc2877 is guaranteed to be at least 6.25 times higher, and drawing proportionally less current, than a standard rs485 load, permitting a total of 200 receivers per contiguous network. the input load of the receiver is unaffected by enabling/disabling the receiver or by powering/depowering the device. ltc 2876/ ltc 2877 28767fa
17 for more information www.linear.com/ltc2876 a pplica t ions i n f or m a t ion balanced signal threshold the ltc2876/ltc2877 differential threshold is 120mv for rising input signals and C120 mv for falling signals. this constitutes 240 mv of hysteresis, which offers a high rejection to signal noise that can otherwise falsely trip a receiver. since these thresholds are centered around zero volts (i.e. balanced), the duty cycle is preserved for small amplitude signals with slewed edgestypical of what is observed at the end of a long cable. figure 11 illustrates this point. in contrast to this, some rs485 receivers have an un - balanced receiver threshold, used to address failsafe conditions ( more on this below). that is, the rising and falling differential signal thresholds are both negative. figure 12 illustrates an example where the rising threshold is C75 mv and falling threshold is C120 mv. this has two disadvantages. first, the hysteresis is only 45 mv in this example, reducing the tolerance to noise, compared to the 240mv of hysteresis in the ltc2876/ltc2877. secondly, these unbalanced thresholds cause a duty cycle or pulse width distortion at the receiver output relative to the input signal. figure 12 illustrates how a competitor part, using the negative thresholds in this example introduces a duty cycle distortion that becomes increasingly worse with low input signal levels and slow input edge rates. failsafe operation the ltc2876 and ltc2877 have a failsafe feature that guarantees the receiver output will be in a logic 1 state (the idle state) when the inputs are shorted, left open, or terminated but not driven for more than about 1.5 s. this failsafe feature is guaranteed to work for inputs spanning the entire common mode range of C25v to +25v. many rs485 receivers simply employ a negative threshold (for rising and falling signals) to achieve failsafe operation. if the inputs are shorted together (0 v differential), the receiver produces a high output, consistent with failsafe. however, this asymmetrical threshold comes with the disadvantages of pulse width distortion and sensitivity to signal noise as described in the section above. the ltc2876/ltc2877 achieves full failsafe operation, while reaping the benefits of a balanced receiver threshold. figure 11. the ltc2876/ltc2877 balanced signal threshold voltages preserve the duty cycle of an incoming signal. the differential signal received ( top ) has a duty cycle of 50%, and is reflected in the receiver output, ro (bottom) figure 12. typical competitor unbalanced signal threshold voltages distort the duty cycle of an incoming signal. input is 50% duty cycle ( top ) but the receiver output is not 50% duty cycle (bottom) failsafe operation is performed with a window compara- tor to determine when the differential input voltage falls between the rising and falling signal thresholds ( v ts +, and v ts C). if this condition persists for more than about 1.5s then the receiver switches over to using the failsafe thresholds (v tfs C, v tfs +), as illustrated in figure 13 and figure 14. the delay allows normal data signals to transition through the threshold region without being interpreted as a failsafe condition, and thus maintaining the benefits of a balanced threshold receiver . however, for fault conditions (e.g., shorted, open, or undriven lines) that persist for more than 1.5 s, the failsafe thresholds are engaged and the receiver output drives high, indicating this condition. the failsafe delay also prevents unwanted receiver output ltc 2876/ ltc 2877 28767fa (pb?pa) ltc2876, ltc2877 - balanced thresholds 28767 f11 +200mv ?200mv 0 v ts + v ts ? ?120mv ?75mv +200mv ro (pb?pa) unbalanced thresholds 28767 f12 ?200mv 0 v ts + v ts ? ?120mv +120mv ro
18 for more information www.linear.com/ltc2876 a pplica t ions i n f or m a t ion glitches resulting from receiver inputs that momentarily cross into the region between the signal rising and falling thresholds as illustrated in figure 14, event 3. s hutdown m ode d ela y the ltc2876 and ltc2877 feature a low power shutdown mode that is entered when both the driver and receiver are simultaneously disabled ( pin de low and re high). a shutdown mode delay of approximately 250ns (not tested in production) is imposed after the state is received before the chip enters shutdown. if either de goes high or re goes low during this delay, the delay timer is reset and the chip does not enter shutdown. this reduces the chance of accidentally entering shutdown if de and re are driven in parallel by a slowly changing signal or if de and re are driven by two independent signals with a timing skew between them. this shutdown mode delay does not affect the outputs of the transmitter and receiver, which start to switch to the high impedance state upon the reception of their respective disable signals as defined by the parameters t shdnd and t shdnr . the shutdown mode delay affects only the time when all the internal circuits that draw dc power from v cc are turned off. p ower -u p /d own g litch -f ree o utputs the ltc2876 and ltc2877 employ an undervoltage detec - tion circuit to control the activation of the on-chip circuitry. during power-up, pb, pa , and ro are undriven, until the v cc supply reaches a voltage sufficient to reliably operate the chip. in this mode, only the internal pull-up resistor on ro and the receiver input resistance to ground on pa and pb offer weak conduction paths at those pins. as the supply voltage rises above the undervoltage threshold, and if the device is configured for drive mode, the pb and pa pins become active and are driven to a state that reflects the input condition on di. likewise, if the device is config - ured for receive mode, the ro pin is driven high or low to reflect the state of the differential voltage across pbC pa . during power down, the reverse occurs; the supply un - dervoltage detection circuit senses low supply voltage and immediately puts the chip into shutdown. the driver and receiver outputs go to the undriven state. ro is pulled up through the internal 250 k pull-up resistor and pa , pb are pulled low through the 125k receiver input resistors. if the ltc2876/ltc2877 is powered or depowered when configured for shutdown (re = 0 v and de = v l (ltc2877) or v cc ( ltc2876) then ro, pb, and pa will remain in the undriven state, without glitching high or low during the supply transition. this allows the powering and depower - ing of the ltc2876/ltc2877 when connected onto a live network without disturbing the lines. figure 13. the ltc2876/ltc2877 signal thresholds (v ts C, v ts +) and failsafe thresholds (v tfs C, v tfs +) figure 14. ltc2876/ltc2877 receiver operation. event 1: signal rises into region between signal thresholds, resulting in the ro transitioning to a failsafe condition after a fixed delay of about 1.5s. event 2: input signal falls below negative signal threshold, resulting in an immediate fall on ro. event 3: signal glitches into the region between signal thresholds for a period less than the failsafe delay time (~1.5s), resulting in an unchanged output. event 4: signal transitions above rising signal threshold, resulting in an immediate rise in ro ltc 2876/ ltc 2877 28767fa +120mv ?v ts v ts ? , v tfs ? v tfs + v ts + ?v tfs +200mv ?200mv 0 v ts + (pb?pa) v tfs + v ts ?, v tfs ? ?120mv +120mv ro (pb?pa) ?75mv 1 2 3 28767 f13 4 28767 f14 ro ?200mv +200mv 0 ?75mv ?120mv
19 for more information www.linear.com/ltc2876 a pplica t ions i n f or m a t ion 60v f ault p rotection tia/eia-485-a specifies that ground shifts between two devices on a network can be as large as C7 v to +12v during operation. most rs485 transceivers cannot safely tolerate voltages on their interface pins that are much higher than this range. however, industrial installations may encounter voltages much greater than this, causing damage to the devices. this requirement means that a driver and receiver sharing communication on a network must be able to operate with a signal common mode voltage difference of C7 v to 12v. competing profibus transceivers can be damaged by pin voltages exceeding these levels by only a few volts . the limited overvoltage tolerance makes implementation of effective external protection networks difficult without interfering with proper data network performance. replac - ing standard rs485 transceivers with the ltc2876 or ltc2877 can eliminate field failures due to overvoltage faults without using costly external protection devices. the 60 v fault protection of the ltc2876/ltc2877 is achieved by using a high voltage bicmos integrated circuit technology. the naturally high breakdown voltage of this technology provides protection in powered off and high impedance conditions. figure 15 further illustrates how the driver and receiver inputs tolerate large voltages above the supply and below ground without excessive device currents. as shown, the driver outputs are reverse-diode protected from voltages back-driven above v cc or below ground. the receiver inputs use resistive dividers that tolerate large positive and negative voltages. the ltc2876/ ltc2877 is protected from 60 v bus faults even with the loss of gnd or v cc . 25v e xtended c ommon m ode r ange the ltc2876 / ltc2877 receiver features an extended com - mon mode r ange of C25 v to +25 v . the wide common mode increases the reliability of operation in environments with high common mode voltages created by electrical noise or local ground potential differences due to ground loops. this extended common mode range allows the ltc2876/ ltc2877 to transmit and receive under conditions that would cause data errors or possible device damage in competing products. v cc pb pa 20:1 divide v cc from di input circuits ltc2876/ltc2877 simplified driver output stage ltc2876/ltc2877 simplified receiver input stage 20:1 divide 28767 f15 to ro output circuits figure 15. internal circuit structure at pa /pb pins that tolerates large positive and negative voltages ltc 2876/ ltc 2877 28767fa
20 for more information www.linear.com/ltc2876 a pplica t ions i n f or m a t ion e lectrical o verstress p rotection equipment used in industrial environments is often ex- posed to extremely high levels of electrical overstress due to phenomena such as electrostatic discharges (esd) from personnel or equipment, electrical fast transients ( eft ) from switching high current inductive loads, and even lightning surges. the ltc2876/ltc2877 has been designed to thrive in these adverse conditions. esd perhaps the most common exposure to electrical over - stress is esd, which results from the build-up of electrical charge on one object, and discharged onto another in close proximity. the ltc2876/ltc2877 features excep- tionally robust esd protection. the bus interface pins (pb and pa ) are protected to 52 kv human body model (hbm) with respect to gnd when unpowered and 26kv with respect to gnd, v cc , or v l when powered, without latchup or damage, in any mode of operation. every other pin on the device is protected to 15 kv esd ( hbm) for all-around robustness. figure 16 shows an unprotected ltc2876 struck repeatedly with 26 kv from an esd gun using air discharge to illustrate the strike energy. the device continues to function normally after the strikes, without damage or cycling the power. figure 16. this single exposure image captures the striking robustness of an unprotected ltc2876 hit repeatedly with 26kv esd discharges while operating without damage or circuit latchup ltc 2876/ ltc 2877 28767fa
21 for more information www.linear.com/ltc2876 the iec standard for esd, iec 61000-4-2, specifies a very fast ( sub-nanosecond) edge transient stimulus intended for system level esd testing and not specified at the device level. however, if it is applied directly to the bus interface pins, without any external protection devices, the ltc2876 / ltc2877 is protected to 4 kv iec when used in a typical ap - plication, powered or unpowered, and terminated with the standard profibus load. this is not tested in production. eft electrical fast transients can result from arcing contacts in switches and relays, common when switching induc - tive loads . the iec standard for e ft is iec61000-4-4 and specifies a repetitive burst pattern lasting 60 seconds. the ltc2876/ltc2877 is robust to eft events and passes the highest level recognized in the iec standard: level 4, 2kv on the pa and pb pins, without any external protection. auxiliary protection for surge surge events represent the most severe transient condi - tions caused by such things as load switching in power distribution systems, high current short circuit faults, and lighting strikes. these are addressed in standard iec 61000-4-5, which specifies repetitive voltage and current waveforms used to deliver high power stimulus lasting tens of microseconds each. the ltc2876/ ltc2877 is designed for high robustness against esd and eft , but the on-chip protection is not able to absorb the energy associated with the iec 61000-4-5 surge transients. external protection is necessary to achieve a high level of surge protection, and can also extend the esd and eft protection to extremely high levels. in addition to providing transient protection, externally con - nected devices must preserve the ability of the ltc2876/ ltc2877 to operate over a wide common mode voltage and yet safely clamp the pin voltage low enough to avoid damage during the overstress event. the added protection must be low in capacitance to avoid excessively loading a pplica t ions i n f or m a t ion the transceiver bus, allowing operation at full data rate. the ltc2876/ltc2877s 60 v pin rating makes it easy to find protection devices meeting these requirements. figure?21 shows a solution providing 4kv protection of the bus interface pins (pa and pb) for all three iec 61000 standards as follows: iec 61000-4-5 2 nd ed . 2005-11 surge level 4: 4kv (line to gnd , 8/20 s waveform, each line coupled to generator through 80 resistor per figure 14 of the standard) iec 61000-4-4 2 nd ed . 2004-07 eft level 4: 4kv (line to gnd , 5 khz repetition rate, 15 ms burst duration every 300 ms, 60 s test duration, discharge coupled to bus pins through 100 pf capacitor per paragraph 7.3.2 of the standard) iec 61000-4-2 2 nd ed . 2008-12 esd level 3: 4kv contact ( line to gnd, direct discharge to bus pins with transceiver and standard profibus resistor load and protection circuit mounted on a ground referenced test card per figure 4 of the standard) the tvs devices in figure 21 have a typical clamp voltage of about 36v , comfortably beyond the ltc2876/ ltc2877 s common mode operating range of 25 v and well below the 60 v rating. since the ltc2876/ltc2877 bus pins are rated for 60 v, the clamping device must maintain volt - ages less than this when conducting peak current during the overstress event. this relatively wide voltage window permits the use of smaller, more resistive clamps, which generally also have less capacitance. tw o of these tvs devices are used in an antiparallel con - figuration because each can only protect in one polarity . the benefit of these uni-directional tvs devices is their low capacitance, offering a total load of only about 50 pf to the signal lines in this configuration, permitting the ltc2876/ ltc2877 to communicate at maximum data rates with no significant performance degradation. ltc 2876/ ltc 2877 28767fa
22 for more information www.linear.com/ltc2876 a pplica t ions i n f or m a t ion b us p ins pa & pb n aming c onvention profibus communicates with rs485 signaling through a differential signal interface. these wires are labeled a and b. the profibus standard specifies that the bus wire b takes on a positive value with respect to bus wire a when no station is transmitting data ( during the idle periods). however, the polarity convention of most rs485 devices uses the opposite convention. that is, with no transmis - sion on the bus, the receiver reports a logic value that would result if a were higher than bin this case a high on ro. from a practical standpoint, this means that if a general rs485 transceiver is connected to a profibus network, the transceivers a pin must connect to the b wire and the b pin connect to the a wire. certainly this can be confusing! since the ltc2876/ltc2877 was designed specifically for profibus applications, the pin naming convention was made to match the profibus specification. to avoid confusion with other rs485 transceivers, the prefix p was added, meaning profibus. if driver and receiver are enabled, a high level on di, will drive the bus lines so that pb is higher than pa and the receiver will report a high level on ro. in profibus installations, connect pb to the b wire (red) and pa to the a wire ( green). for non-profibus rs485 applications, the pb pin should be connected to the a signal and pa pin should be connect to the b signal to match the convention of most other rs485 devices. profibus c ables it is recommended that profibus installations use cable designed for profibus applications. typically, type a cable and termination is used. this is a shielded twisted pair with the following properties: table 1. profibus type-a cable properties property value impedance 135 to 165 capacitance < 30pf/m loop resistance < 110/km conductor area 0.34mm 2 color of sheath (non-is) violet color of inner conductor a green color of inner conductor b red the three resistors that make up the termination network should be placed at both ends of the bus and must be powered during operation. if there are multiple nodes communicating on the bus, only the nodes at the ends should be terminated. the cable shield helps to improve electromagnetic com - patibility ( emc). it is recommended to ground both ends of the shield, through the case of the connector, to the chassis of the connected station. in applications where ground potential differences exist between stations, for example long distance transmission between buildings, the shield should be grounded only at one end of the cable. if the potential difference exceeds several volts, galvanic isolation is recommended at one or more of the con - nected stations . in this case, consider using the lt m ? 2892 module isolator ( see 3500v rms isolated profibus node with termination on the last page). if the shield cannot be grounded through the connector case, pin 1 of the d-sub connector can be used as an alternative, although the added inductance makes this sub-optimal. in such a case, it is better to bare the cable shield at an appropriate point and ground it with a short cable or clamp to the metallic structure of the station. unshielded cable can be used in profibus installations if there is no severe electromagnetic interference ( emi). do not use cables that are untwisted pairs. ltc 2876/ ltc 2877 28767fa
23 for more information www.linear.com/ltc2876 m12 plug m12 socket 9-pin d-sub figure 17. connector pin allocations a pplica t ions i n f or m a t ion the d-sub connector is specified for use up to 12mbps. inductors are often built into the cable connectors to reduce unwanted ringing and reflections at data rates above 1.5 mbits/s. cable connectors are also available with termination resistors that can be switched in/out. table 3. pin designation for d-sub and m12 connectors. (connections in bold are mandatory) pin number connection 9-pin d-sub m12 1, case thread cable shield 2 gnd for 24v supply 3 4 pb (b C red wire) 4 cntr-p (repeater direction control) 5 3 gnd for bus t ermination 6 1 v cc (+5v) for bus termination 7 +24v supply 8 2 pa (a C green wire) 9 cntr-n (repeater direction control) 5 not used o peration in rs485 and rs422 s ystems the ltc2876 and ltc2877 are completely compatible with standard rs485 and rs422 networks. in these in - stallations, the pb pin should be treated as the a pin for compatibility with most rs485 transceivers. likewise, the pa pin should be matched up with the b signal in rs485. further discussion about this can be found in section bus pins pa and pb naming convention. twisted pair cables with characteristic impedance of 120 or 100 can be used. shielded cable is recommended for the highest electromagnetic compatibility ( emc), but unshielded cable like cat -5e works well. untwisted pair cables ( utp) should be avoided. both ends of a cable should be terminated differentially with resistors that match the cables impedance, as illustrated in figure 10. sometimes bus biasing resistors are used for non- profibus rs 485 installations to introduce a high level (idle state) on the bus when nothing is driving it. an example of such a network is shown in figure 18 1 . here the three resistors (620?, 130 ?, and 620 ?) replace the single 120 ? differential resistor in one location only. m aximum profibus c able l ength the following table gives the maximum cable segment lengths at profibus baud rates, as specified in iec 61158-2: table 2. profibus maximum cable length baud rate (kbits/s) max. segment length (m) 9.6 1200 19.2 1200 45.45 1200 93.75 1200 187.5 1000 500 400 1500 200 3000 100 6000 100 12000 100 c onnectors the profibus standard only specifies the use of a 9-pin d-sub connector for stations and cables. a commonly used alternative is the 5-pin b-coded m12 circular con - nectors (iec 947-5-2). in all cases, the female side of the connector is located in the station, while the cable uses the male end. connector diagrams are shown in figure 17 and pin designations are shown in table 3. ltc 2876/ ltc 2877 28767fa 9 1 2 3 5 5 4 1 4 3 5 2 28767 f16 6 3 8 1 2 4 7
24 for more information www.linear.com/ltc2876 figure 18. using the ltc2876/ltc2877 in an rs485 network (not profibus) with optional bus bias resistors a pplica t ions i n f or m a t ion unlike profibus, the biasing network is not part of the rs485 standard. although the ltc2876 and ltc2877 are compatible with this biasing arrangement, the inter - nal failsafe feature eliminates the need for it, since an undriven bus triggers a failsafe condition. in extremely noisy environments the resistor biasing helps reinforce the failsafe condition. v l l ogic s upply a separate logic supply pin v l allows the ltc2877 to interface with any logic signal from 1.65 v to 5.5 v. all logic i/os use v l as their high supply. it is recommended that v l does not exceed v cc during operation. if v l does exceed v cc , no damage will occur but the v l supply current could increase about 300 a, depending on the operating configuration and the state of the device. if v l is not con- nected to v cc , bypass v l with a 0.1 f capacitor to gnd. the driver is disabled and pins pb and pa are undriven when v l or v cc is grounded or disconnected. 3.3v o pera tion the ltc2876 and ltc2877 can be used with a supply voltage as low as 3.0 v in rs485 installations. reducing the supply voltage reduces the driver output signal swing below what is specified in the rs485 standard but still produces signals much larger than the 200 mv minimum signal swing required at the receiver input. a plot in the typical characteristics section shows the driver output signal for 3.3v and 5v supply voltages. 3.3v-powered ltc2876/ltc2877 devices can be mixed with other rs485 transceivers running from 5 v on the same network as shown in figure 20. there is no concern for the higher voltage of a 5 v node overdriving the 3.3 v node due to the overvoltage-tolerant design of the ltc2876/ ltc2877, as illustrated in figure 15. one advantage to using a lower supply voltage is reduced v cc current draw. v cc supply currents are roughly pro- portional to the applied supply voltage when the ltc2876/ ltc2877 is driving loads. the typical characteristics section shows the typical power supply currents versus transmission rates for 3.3v and 5v supplies. profibus installations that use the ltc2876/ltc2877 with supply voltages less than 4.5 v, may fall out of com - pliance to the profibus specification. h igh s peed c onsidera tions a ground plane layout with a 1 f bypass capacitor placed less than 7 mm away from v cc is recommended. the pc board traces connected to signal pb and pa should be symmetrical and as short as possible to maintain good differential signal integrity. to minimize capacitive effects, the differential signals should be separated by more than the width of a trace and should not be routed on top of each other if they are on different signal planes. care should be taken to route the outputs away from the sensitive inputs to reduce feedback effects that might cause noise, jitter, and even oscillations. for example, di and ro should not be routed next to each other or next to pb and pa . logic inputs have a typical hysteresis of about 150 mv to provide noise immunity. fast edges on the outputs can cause glitches in the ground and power supplies which are exacerbated by capacitive loading. if a logic input is held near its threshold ( typically v cc /2 or v l / 2), a noise glitch from a driver transition may exceed the hysteresis levels on the logic and data input pins, causing an unintended state change. this can be avoided by maintaining normal logic levels on the pins and by slewing inputs faster than 1v/s. good supply decoupling and proper driver termi - nation also reduces glitches caused by driver transitions. r eferences 1 application guidelines for tia/eia-485-a: tsb-89-a, tia telecommunications system bulletin, january 2006. ltc 2876/ ltc 2877 28767fa bus bias resistors at one end 620 620 28767 f17 130 5v 120 ltc2876 or ltc2877 ltc2876 or ltc2877
25 for more information www.linear.com/ltc2876 a pplica t ions i n f or m a t ion figure 19. complete configuration for profibus operation using the (a) ltc2876, or (b) ltc2877 and (c) the cable with termination resistors ltc 2876/ ltc 2877 28767fa v cc di re ro de pa pb ltc2876 c 5 sensor 6 3 8 9-pin d-sub connector (female) 1 gnd (a) (b) gnd pa 1f pb sensor v cc 4.5v to 5.5v 1.65v to 5.5v v cc v cc v l v l di v cc re ro de pa pb ltc2877 c 5 6 3 4.5v to 5.5v 8 9-pin d-sub connector (female) 1 gnd gnd pa pb shield profibus cable (z o = 150) termination resistor strings switched in to signal lines if located at bus end 0.1f b a 390 390 220 9-pin d-sub connector (male) 9-pin d-sub connector (male) 5 6 3 1f 8 1 5 6 3 8 1 390 390 220 28767 f18 (c) v cc
26 for more information www.linear.com/ltc2876 figure 20. ltc2876/ltc2877 operation as low as 3v is compatible with other rs485 devices, but with reduced output signal swing a pplica t ions i n f or m a t ion figure 21. exceptionally robust, low-capacitance, 30v tolerant, 4kv iec 61000 bus protection against surge, eft , and esd. (see auxiliary protection for surge, eft , and esd in the applications information section for more details) ltc 2876/ ltc 2877 28767fa 3v to 5.5v a b 3.3v or 5v rs485 node 28767 f19 ltc2876/ ltc2877 pa pb pa pb tvs tvs tvs 28767 f21 tvs tvs: littlefuse sacb30 120 120 3v to 5.5v ltc2876/ ltc2877 pa pb v cc
27 for more information www.linear.com/ltc2876 p ackage descrip t ion dd package 8-lead plastic dfn (3mm 3mm) (reference ltc dwg # 05-08-1698 rev c) 3.00 0.10 (4 sides) note: 1. drawing to be made a jedec package outline m0-229 variation of (weed-1) 2. drawing not to scale 3. all dimensions are in millimeters 4. dimensions of exposed pad on bottom of package do not include mold flash. mold flash, if present, shall not exceed 0.15mm on any side 5. exposed pad shall be solder plated 6. shaded area is only a reference for pin 1 location on top and bottom of package 0.40 0.10 bottom view?exposed pad 1.65 0.10 (2 sides) 0.75 0.05 r = 0.125 typ 2.38 0.10 1 4 8 5 pin 1 top mark (note 6) 0.200 ref 0.00 ? 0.05 (dd8) dfn 0509 rev c 0.25 0.05 2.38 0.05 recommended solder pad pitch and dimensions apply solder mask to areas that are not soldered 1.65 0.05 (2 sides) 2.10 0.05 0.50 bsc 0.70 0.05 3.5 0.05 package outline 0.25 0.05 0.50 bsc dd package 8-lead plastic dfn (3mm 3mm) (reference ltc dwg # 05-08-1698 rev c) please refer to http://www .linear.com/product/ltc2876#packaging for the most recent package drawings. ltc 2876/ ltc 2877 28767fa
28 for more information www.linear.com/ltc2876 p ackage descrip t ion dd package 10-lead plastic dfn (3mm 3mm) (reference ltc dwg # 05-08-1699 rev c) 3.00 0.10 (4 sides) note: 1. drawing to be made a jedec package outline m0-229 variation of (weed-2). check the ltc website data sheet for current status of variation assignment 2. drawing not to scale 3. all dimensions are in millimeters 4. dimensions of exposed pad on bottom of package do not include mold flash. mold flash, if present, shall not exceed 0.15mm on any side 5. exposed pad shall be solder plated 6. shaded area is only a reference for pin 1 location on the top and bottom of package 0.40 0.10 bottom view?exposed pad 1.65 0.10 (2 sides) 0.75 0.05 r = 0.125 typ 2.38 0.10 (2 sides) 1 5 10 6 pin 1 top mark (see note 6) 0.200 ref 0.00 ? 0.05 (dd) dfn rev c 0310 0.25 0.05 2.38 0.05 (2 sides) recommended solder pad pitch and dimensions 1.65 0.05 (2 sides) 2.15 0.05 0.50 bsc 0.70 0.05 3.55 0.05 package outline 0.25 0.05 0.50 bsc dd package 10-lead plastic dfn (3mm 3mm) (reference ltc dwg # 05-08-1699 rev c) pin 1 notch r = 0.20 or 0.35 45 chamfer please refer to http://www .linear.com/product/ltc2876#packaging for the most recent package drawings. ltc 2876/ ltc 2877 28767fa
29 for more information www.linear.com/ltc2876 p ackage descrip t ion ms8e package 8-lead plastic msop, exposed die pad (reference ltc dwg # 05-08-1662 rev k) msop (ms8e) 0213 rev k 0.53 0.152 (.021 .006) seating plane note: 1. dimensions in millimeter/(inch) 2. drawing not to scale 3. dimension does not include mold flash, protrusions or gate burrs. mold flash, protrusions or gate burrs shall not exceed 0.152mm (.006") per side 4. dimension does not include interlead flash or protrusions. interlead flash or protrusions shall not exceed 0.152mm (.006") per side 5. lead coplanarity (bottom of leads after forming) shall be 0.102mm (.004") max 6. exposed pad dimension does include mold flash. mold flash on e-pad shall not exceed 0.254mm (.010") per side. 0.18 (.007) 0.254 (.010) 1.10 (.043) max 0.22 ? 0.38 (.009 ? .015) typ 0.86 (.034) ref 0.65 (.0256) bsc 0 ? 6 typ detail ?a? detail ?a? gauge plane 1 2 3 4 4.90 0.152 (.193 .006) 8 8 1 bottom view of exposed pad option 7 6 5 3.00 0.102 (.118 .004) (note 3) 3.00 0.102 (.118 .004) (note 4) 0.52 (.0205) ref 1.68 (.066) 1.88 (.074) 5.10 (.201) min 3.20 ? 3.45 (.126 ? .136) 1.68 0.102 (.066 .004) 1.88 0.102 (.074 .004) 0.889 0.127 (.035 .005) recommended solder pad layout 0.65 (.0256) bsc 0.42 0.038 (.0165 .0015) typ 0.1016 0.0508 (.004 .002) detail ?b? detail ?b? corner tail is part of the leadframe feature. for reference only no measurement purpose 0.05 ref 0.29 ref ms8e package 8-lead plastic msop, exposed die pad (reference ltc dwg # 05-08-1662 rev k) please refer to http://www .linear.com/product/ltc2876#packaging for the most recent package drawings. ltc 2876/ ltc 2877 28767fa
30 for more information www.linear.com/ltc2876 p ackage descrip t ion mse package 10-lead plastic msop, exposed die pad (reference ltc dwg # 05-08-1664 rev i) msop (mse) 0213 rev i 0.53 0.152 (.021 .006) seating plane 0.18 (.007) 1.10 (.043) max 0.17 ?0.27 (.007 ? .011) typ 0.86 (.034) ref 0.50 (.0197) bsc 1 2 3 4 5 4.90 0.152 (.193 .006) 0.497 0.076 (.0196 .003) ref 8910 10 1 7 6 3.00 0.102 (.118 .004) (note 3) 3.00 0.102 (.118 .004) (note 4) note: 1. dimensions in millimeter/(inch) 2. drawing not to scale 3. dimension does not include mold flash, protrusions or gate burrs. mold flash, protrusions or gate burrs shall not exceed 0.152mm (.006") per side 4. dimension does not include interlead flash or protrusions. interlead flash or protrusions shall not exceed 0.152mm (.006") per side 5. lead coplanarity (bottom of leads after forming) shall be 0.102mm (.004") max 6. exposed pad dimension does include mold flash. mold flash on e-pad shall not exceed 0.254mm (.010") per side. 0.254 (.010) 0 ? 6 typ detail ?a? detail ?a? gauge plane 5.10 (.201) min 3.20 ? 3.45 (.126 ? .136) 0.889 0.127 (.035 .005) recommended solder pad layout 1.68 0.102 (.066 .004) 1.88 0.102 (.074 .004) 0.50 (.0197) bsc 0.305 0.038 (.0120 .0015) typ bottom view of exposed pad option 1.68 (.066) 1.88 (.074) 0.1016 0.0508 (.004 .002) detail ?b? detail ?b? corner tail is part of the leadframe feature. for reference only no measurement purpose 0.05 ref 0.29 ref mse package 10-lead plastic msop, exposed die pad (reference ltc dwg # 05-08-1664 rev i) please refer to http://www .linear.com/product/ltc2876#packaging for the most recent package drawings. ltc 2876/ ltc 2877 28767fa
31 for more information www.linear.com/ltc2876 information furnished by linear technology corporation is believed to be accurate and reliable. however, no responsibility is assumed for its use. linear technology corporation makes no representa- tion that the interconnection of its circuits as described herein will not infringe on existing patent rights. r evision h is t ory rev date description page number a 08/16 changed test condition for t plhr and t phlr 5 ltc 2876/ ltc 2877 28767fa
32 for more information www.linear.com/ltc2876 ? linear technology corporation 2016 lt 0816 rev a ? printed in usa linear technology corporation 1630 mccarthy blvd., milpitas, ca 95035-7417 (408) 432-1900 fax : (408) 434-0507 www.linear.com/ltc2876 r ela t e d p ar t s typical a pplica t ion part number description comments ltc2862/ltc2863/ ltc2864/ltc2865 60v fault protected 3v to 5.5v rs485/rs422 transceivers 60v tolerant, 15kv esd, 250kbps or 20mbps ltc2856/ltc2857/ ltc2858 5v 20mbps and slew rate limited 15kv rs485/rs422 transceivers 15kv esd, 250kbps or 20mbps ltc2850/ltc2851/ ltc2852 3.3v 20mbps rs485 transceivers 15kv esd ltc2854/ltc2855 3.3v 20mbps rs485 transceivers with integrated switchable termination 25kv esd (ltc2854), 15kv esd (ltc2855) ltc2859, ltc2861 5v 20mbps and slew rate limited rs485 transceivers 15kv esd LTM2881 complete 3.3v or 5v isolated rs485 module transceiver + power, and switchable integrated termination resistor 2500v rms isolation, with integrated isolated dc/dc converter, 1w power, low emi, 15kv esd, 30kv/s transient immunity ltm 2892 3500v rms 6-channel digital isolator 3500v rms isolation in a small package with temperature ratings up to 125c 3500v rms isolated profibus node with termination ltc 2876/ ltc 2877 28767fa outa outb outc ind ine inf gnd2 v cc1 v l1 on1 390 eoutd ina inb inc outd oute outf gnd1 isolation barrier gnd2 390 a6 a5 a4 b4 gnd1 a1 a2 a3 b1 b2 28767 ta02 b3 b5 b6 j6 j5 j4 j1 j2 j3 h3 220 h2 h1 h4 h5 h6 ltm2892-s 1 8 2 4 v cc2 3 5 7 6 3v to 5.5v ro di d r 1 2 v l2 3 4 isolated ground m12 connector (female) isolated 5v in gnd di re ro de on2 pa pb ltc2876 v cc eouta

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