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exar corporation 48720 kato road, fremont ca, 94538 ? (510) 668-7000 ? fax (510) 668-7017 ? www.exar.com xr3170e-3178e 3.3v high speed rs-485/rs-422 transceivers with 1/8 th unit load december 2009 rev. 1.0.0 general description the xr3170e - xr3178e family of rs-485 devices are designed for reliable, bidirectional communication on multipoint bus transm ission lines. each device contains one differential driver and one differential receiver. xr3172e , xr3175e and xr3178e are half- duplex devices; other part numbers are full-duplex. all devices comply with ti a/eia-485 and tia/eia-422 standards. lead free and rohs compliant packages are available for all models. these devices are ruggedized for use in harsh o perating conditions over the entire common-mode voltage range from -7v to +12v. receivers are specially designed to fail-safe to a logic high output state if the inputs are left un-driven or shorted. all rs- 485 bus pins are protected against severe esd events up to +/-15kv (air-gap and human body model) and up to +/-8kv contact discharge (iec 61000-4-2). drivers are protected from excess current flow caused by bus contention or output short-circuits by both an internal current limit and a thermal-overload shutdown. devices are rated for industrial (-40 to +85c) operating temperatures. receivers have exceptionally high input impedance, which places only 1/8 th the standard load on a shared bus. up to 256 transcei vers may coexist while preserving full signal margin. all devices operate from a single 3.3v power supply a nd draw negligible quiescent power. all versions except the xr3171e, xr3174e and xr3177e may independently enable and disable their driver and receiver and enter a low power shutdown mode if both driver and receiver are disabled. all outputs maintain high impedance in shutdown or when powered off. features ? 3.3v single supply operation ? high speed 20mbps data rate ? slew rate limited - 250kbps and 500kbps data rate ? 1/8 th unit load, 256 transceivers on bus ? enhanced failsafe for receiver - open, short or terminated lines ? robust esd protection for rs-485 pins +/-15kv air-gap discharge +/-15kv human body model +/-8kv contact discharge ? hot swap glitch protection ? driver short circuit current limit and thermal shutdown for overload protection ? ultra-low 650ua qu iescent current ? 1 a shutdown mode ? industry standard package footprints typical applications ? motor control ? building automation ? security systems ? remote utility meter reading ? long or un-terminated transmission lines f igure 1. t ypical a pplication c ircuit r t r t stub xr3178e xr3178e xr3178e xr3178e a aa a b bb b di ro re de de de de re re di di di ro ro ro re
f igure 2. p in o ut a ssignment nc nc vcc 2 1 3 4 5 6 78 9 10 11 12 13 14 di nc ro re de gnd gnd y z b a 2 1 3 45 6 7 8 vcc ro di gnd a b z y 2 1 3 45 6 7 8 8-pin nsoic half duplex xr3172e xr3175e xr3178e ro re de di gnd a b vcc 8-pin nsoic full duplex xr3171e xr3174e xr3177e 14-pin nsoic full duplex xr3170e xr3173e xr3176e ordering information p art n umber p ackage o perating t emperature r ange d evice s tatus xr3170eid 14-pin narrow soic -40c to +85c active xr3171eid 8-pin narrow soic -40c to +85c active xr3172eid 8-pin narrow soic -40c to +85c active xr3173eid 14-pin narrow soic -40c to +85c active xr3174eid 8-pin narrow soic -40c to +85c active XR3175EID 8-pin narrow soic -40c to +85c active xr3176eid 14-pin narrow soic -40c to +85c active xr3177eid 8-pin narrow soic -40c to +85c active xr3178eid 8-pin narrow soic -40c to +85c active xr3170e-3178e 2 3.3v high speed rs-485/rs-422 transceivers with 1/8 th unit load rev. 1.0.0 note: please visit www.exar.com for ta pe and reel option part numbers.
xr3170e-3178e 3 rev. 1.0.0 3.3v high speed rs-485/rs- 422 transceivers with 1/8 th unit load pin descriptions pin assignments p in n umber p in n ame t ype d escription h alf d uplex f ull d uplex 1 2 2 ro o receiver output. when re is low and if (a- b) -50mv, ro is high. if (a-b) -200mv, ro is low. 2 - 3 re i receiver output enable. when re is low, ro is enabled. when re is high, ro is high impedance. re should be high and de should be low to enter shutdown mode. re is a hot-swap input. 3 - 4 de i driver output enable. when de is high, output s are enabled. when de is low, out - puts are high impedance. de should be low and re should be high to enter shutdown mode. de is a hot-swap input. 4 3 5 di i driver input. with de hi gh, a low level on di forces non-inverting output low and invert - ing output high. similarly, a high level on di fo rces non-inverting output high and invert - ing output low. 5 4 6, 7 gnd pwr ground. 6 - - a i/o non-inverting receiver input and non- in verting driver output. 7 - - b i/o inverting receiver input and inverting driver ou tput. 8 1 14 vcc pwr +3.3v power supply input. bypass with 0.1uf capacitor. - 8 12 a i non-inverting receiver input. - 7 11 b i inverting reciever input. - 5 9 y o non-inverting driver output. - 6 10 z o inverting driver output. - - 1, 8, 13 nc - no connect, not internally connected. pin type: i=input, o=output. xr3172e xr3175e xr3178e xr3171e xr3174e xr3177e xr3170e xr3173e xr3176e
absolute maximum ratings these are stress ratings only and functional operation of the dev ice at these ratings or any other above those indicated in the operation sections to the specifications below is not implied. ex posure to absolute maximum rating conditions for extended periods of time may affect re liability and cause permanent damage to the device. v cc +6.0v input voltage at control pins ( re , de and di) -0.3v to (v cc + 0.3v) driver output voltage (a, b, y and z) -8v to +13v receiver output voltage (ro) -0.3v to (v cc + 0.3v) receiver input voltage (a and b) -8v to +13v storage temperature range -65c to + 150c lead temperature (soldering, 10s) +300c package power dissipation maximum junction temperature 150c 8-pin so ja = 128.4c/w 14-pin so ja = 86c/w xr3170e-3178e 4 3.3v high speed rs-485/rs-422 transceivers with 1/8 th unit load rev. 1.0.0 caution: esd (electrostatic discharge) sensitive device. permanent dama ge may occur on unconnected devices subject to high energy elect rostatic fields. unused devices must be stored in conductive foam or shunts. personnel should be properly grounded prior to handling this device. the protective foam should be discharged to the destination so cket before devices are removed. electrical characteristics u nless otherwise noted : v cc = +3.0v to +3.6v with t a from -40 o c to +85 o c. t ypical values are at v cc = +3.3v and 25 o c. s ymbol p arameters m in . typ. m ax . u nits c onditions driver dc characteristics v od differential driver output vcc v no load 2.0 2.65 r l = 100 ? (rs-422), figure 3 1.7 2.35 r l = 54 ? (rs-485), figure 3 1.7 2.35 v cm = -7v, figure 4 1.7 2.35 v cm = +12v, figure 4 ? v od change in magnitude of differential output -0.20 0.20 v r l = 100 ? (rs-422), figure 3, see note 1 -0.20 0.20 r l = 54 ? (rs-485), figure 3, see note 1 -0.20 0.20 v cm = -7v, figure 4, see note 1 -0.20 0.20 v cm = +12v, figure 4, see note 1 v oc driver common mode output voltage steady state 3.0 v figure 3
xr3170e-3178e 5 rev. 1.0.0 3.3v high speed rs-485/rs- 422 transceivers with 1/8 th unit load ? v oc change in magnitude of common mode output voltage -0.2 0.2 v figure 3, see note 1 i osd driver short circuit current limit -250 250 ma -7v v out 12v, figure 5 v ih logic input thresholds (di, de, re ) 2.0 v logic input high v il 0.8 v logic input low v hys driver input hysteresis 100 mv t a = 25c i in logic input current (di, de and re ) -1 1 a 0v in +vcc, after first tran - sition, note 2 i ol output leakage current (full-duplex versions, y and z pins) note 2 125 a vout = 12v, de = 0v, re = 0v, vcc = 0v or 3.3v. -100 a vout = -7v, de = 0v, re = 0v, vcc = 0v or 3.3v. receiver dc characteristics r in receiver input resistance 96 160 k? -7v v cm 12v i in input current (a, b pins) 70 125 a de = 0v, vcc = 0v or 3.3v, v in = 12v -100 -55 a de = 0v, vcc = 0v or 3.3v, v in = -7v v ih, v il receiver differential thresholds (v a - v b ) -200 -120 -50 mv -7v v cm 12v receiver input hysteresis 25 mv v cm = 0v v oh receiver output voltage high vcc - 0.6 v i out = -8ma, v id = -50mv v ol receiver output voltage low 0.4 v i out = 8ma, v id = -200mv i oz high-z receiver output current +/- 0.03 +/-1.0 a vcc = 3.3v, 0.40v vout 2.4v i osc receiver output short circuit cur - rent +/-95 ma 0v v ro vcc supply and protection i cc1 supply current - driver enabled 650 950 a no load, de = vcc, di = 0v or vc c i cc2 supply current - shutdown mode 1 a de = 0v, re = vcc, di = 0v or vcc t sd thermal shutdown temperature 165 c junction temperature, note 4 thermal shutdown hysteresis 15 c note 4 xr3170e, xr3171e, xr3172e driver ac characteristics freq max. data signaling rate 250 kbps 1/t ui , duty cycle 40 to 60% u nless otherwise noted : v cc = +3.0v to +3.6v with t a from -40 o c to +85 o c. t ypical values are at v cc = +3.3v and 25 o c. s ymbol p arameters m in .typ.m ax .u nits c onditions
xr3170e-3178e 6 3.3v high speed rs-485/rs-422 transceivers with 1/8 th unit load rev. 1.0.0 t plh driver propagation delay (low to high) 250 1500 ns c l = 50pf, r l = 54 ?, figures 6 and 7 t phl driver propagation delay (high to low) 250 1500 ns c l = 50pf, r l = 54 ?, figures 6 and 7 t r driver rise time 350 1600 ns c l = 50pf, r l = 54 ?, figures 6 and 7 t f driver fall time 350 1600 ns c l = 50pf, r l = 54 ?, figures 6 and 7 | t plh- t phl | differential pulse skew 200 ns figures 6 and 7 t zh driver enable to output high 2500 ns c l = 50pf, r l = 500 ?, figures 8 and 9 t zl driver enable to output low 2500 ns c l = 50pf, r l = 500 ?, figures 10 and 11 t hz driver disable from output high 150 ns c l = 50pf, r l = 500 ?, figures 8 and 9 t lz driver disable from output low 150 ns c l = 50pf, r l = 500 ?, figures 10 and 11 t ozv shutdown to driver output valid 3500 ns c l = 50pf, r l = 500 ? t shdn time to shutdown 50 200 600 ns notes 3 and 4 receiver ac characteristics freq data signaling rate 250 kbps 1/t ui , duty cycle 40 to 60% t plh receiver propagation delay (low to high) 200 ns v id = +/-2v, c l = 15pf, figures 12 and 13 t phl receiver propagation delay (high to low) 200 ns v id = +/-2v, c l = 15pf, figures 12 and 13 skew receiver propagation delay skew 30 ns v id = +/-2v, c l = 15pf, figures 12 and 13 skew = | t plh- t phl | t r receiver output rise time 3 6 ns c l = 15pf, figure 12 t f receiver output fall time 3 6 ns c l = 15pf, figure 12 t zh receiver enable to output high 50 ns c l = 15pf, figure 14 t zl receiver enable to output low 50 ns c l = 15pf, figure 14 t hz receiver disable from output high 50 ns c l = 15pf, figure 14 t lz receiver disable from output low 50 ns c l = 15pf, figure 14 t zh(shdn) shutdown to receiver output valid high 3500 ns c l = 15pf, figure 14 t zl(shdn) shutdown to receiver output valid low 3500 ns c l = 15pf, figure 14 u nless otherwise noted : v cc = +3.0v to +3.6v with t a from -40 o c to +85 o c. t ypical values are at v cc = +3.3v and 25 o c. s ymbol p arameters m in .typ.m ax .u nits c onditions
xr3170e-3178e 7 rev. 1.0.0 3.3v high speed rs-485/rs- 422 transceivers with 1/8 th unit load t shdn time to shutdown 50 200 600 ns notes 3 and 4 xr3173e, xr3174e and xr3175e driver ac characteristics freq max. data signaling rate 500 kbps 1/t ui , duty cycle 40 to 60% t plh driver propagation delay (low to high) 180 800 ns c l = 50pf, r l = 54 ?, figures 6 and 7 t phl driver propagation delay (high to low) 180 800 ns c l = 50pf, r l = 54 ?, figures 6 and 7 t r driver rise time 200 800 ns c l = 50pf, r l = 54 ?, figures 6 and 7 t f driver fall time 200 800 ns c l = 50pf, r l = 54 ?, figures 6 and 7 | t plh- t phl | differential pulse skew 100 ns figures 6 and 7 t zh driver enable to output high 2500 ns c l = 50pf, r l = 500 ?, figures 8 and 9 t zl driver enable to output low 2500 ns c l = 50pf, r l = 500 ?, figures 10 and 11 t hz driver disable from output high 150 ns c l = 50pf, r l = 500 ?, figures 8 and 9 t lz driver disable from output low 150 ns c l = 50pf, r l = 500 ?, figures 10 and 11 t ozv shutdown to driver output valid 3500 ns c l = 50pf, r l = 500 ? t shdn time to shutdown 50 200 600 ns notes 3 and 4 receiver ac characteristics freq data signaling rate 500 kbps 1/t ui , duty cycle 40 to 60% t plh receiver propagation delay (low to high) 200 ns v id = +/-2v, c l = 15pf, figures 12 and 13 t phl receiver propagation delay (high to low) 200 ns v id = +/-2v, c l = 15pf, figures 12 and 13 skew receiver propagation delay skew 30 ns v id = +/-2v, c l = 15pf, figures 12 and 13 skew = | t plh- t phl | t r receiver output rise time 3 6 ns c l = 15pf t f receiver output fall time 3 6 ns c l = 15pf t zh receiver enable to output high 50 ns c l = 15pf, figure 14 t zl receiver enable to output low 50 ns c l = 15pf, figure 14 t hz receiver disable from output high 50 ns c l = 15pf, figure 14 u nless otherwise noted : v cc = +3.0v to +3.6v with t a from -40 o c to +85 o c. t ypical values are at v cc = +3.3v and 25 o c. s ymbol p arameters m in .typ.m ax .u nits c onditions
xr3170e-3178e 8 3.3v high speed rs-485/rs-422 transceivers with 1/8 th unit load rev. 1.0.0 t lz receiver disable from output low 50 ns c l = 15pf, figure 14 t zh(shdn) shutdown to receiver output valid high 3500 ns c l = 15pf, figure 14 t zl(shdn) shutdown to receiver output valid low 3500 ns c l = 15pf, figure 14 t shdn time to shutdown 50 200 600 ns notes 3 and 4 xr3176e, xr3177e and xr3178e driver ac characteristics freq max. data signaling rate 20 mbps 1/t ui , duty cycle 40 to 60% t plh driver propagation delay (low to high) 4 12 40 ns c l = 50pf, r l = 54 ?, figures 6 and 7 t phl driver propagation delay (high to low) 4 12 40 ns c l = 50pf, r l = 54 ?, figures 6 and 7 t r driver rise time 2 3 10 ns c l = 50pf, r l = 54 ?, figures 6 and 7 t f driver fall time 2 3 10 ns c l = 50pf, r l = 54 ?, figures 6 and 7 | t plh- t phl | differential pulse skew 5 ns figures 6 and 7 t zh driver enable to output high 150 ns c l = 50pf, r l = 500 ?, figures 8 and 9 t zl driver enable to output low 150 ns c l = 50pf, r l = 500 ?, figures 10 and 11 t hz driver disable from output high 150 ns c l = 50pf, r l = 500 ?, figures 8 and 9 t lz driver disable from output low 150 ns c l = 50pf, r l = 500 ?, figures 10 and 11 t ozv shutdown to driver output valid 3500 ns c l = 50pf, r l = 500 ? t shdn time to shutdown 50 200 600 ns notes 3 and 4 receiver ac characteristics freq data signaling rate 20 mbps 1/t ui , duty cycle 40 to 60% t plh receiver propagation delay (low to high) 4 22 40 ns v id = +/-2v, c l = 15pf, figures 12 and 13 t phl receiver propagation delay (high to low) 4 22 40 ns v id = +/-2v, c l = 15pf, figures 12 and 13 skew receiver propagation delay skew 5 ns v id = +/-2v, c l = 15pf, figures 12 and 13 skew = | t plh- t phl | t r receiver output rise time 3 6 ns c l = 15pf u nless otherwise noted : v cc = +3.0v to +3.6v with t a from -40 o c to +85 o c. t ypical values are at v cc = +3.3v and 25 o c. s ymbol p arameters m in .typ.m ax .u nits c onditions
xr3170e-3178e 9 rev. 1.0.0 3.3v high speed rs-485/rs- 422 transceivers with 1/8 th unit load n ote : 1. change in magnitude of dif ferential output voltage and change in magnitude of common mode output voltage are the changes in output voltage when di input changes state. 2. except devices which do not have de or re inputs. 3. the transceivers are put into shutdown by bringing re high and de low simultaneously for at least 600ns. if the control inputs are in this state for less than 50ns, the devi ce is guaranteed not enter shutdown. if the enable inputs are held in this state for at least 600ns the device is assur ed to be in shutdown. note that the receiver and driver enable times increase during shutdown. 4. guaranteed by design and bench characterization. t f receiver output fall time 3 6 ns c l = 15pf t zh receiver enable to output high 50 ns c l = 15pf, figure 14 t zl receiver enable to output low 50 ns c l = 15pf, figure 14 t hz receiver disable from output high 50 ns c l = 15pf, figure 14 t lz receiver disable from output low 50 ns c l = 15pf, figure 14 t zh(shdn) shutdown to receiver output valid high 3500 ns c l = 15pf, figure 14 t zl(shdn) shutdown to receiver output valid low 3500 ns c l = 15pf, figure 14 t shdn time to shutdown 50 200 600 ns notes 3 and 4 u nless otherwise noted : v cc = +3.0v to +3.6v with t a from -40 o c to +85 o c. t ypical values are at v cc = +3.3v and 25 o c. s ymbol p arameters m in .typ.m ax .u nits c onditions
f igure 3. d river dc t est c ircuit r l /2 r l /2 v oc d v cc v od di f igure 4. d river c ommon m ode l oad t est a/y b/z d di = 0 or vcc 60? de = 3.3v v od 375? 375? v cm f igure 5. d river s hort c ircuit c urrent l imit t est a/y d di = 0 or vcc b/z de = 0 or vcc i os d -7v to +12v v xr3170e-3178e 10 3.3v high speed rs-485/rs-422 transceivers with 1/8 th unit load rev. 1.0.0
f igure 6. d river p ropagation d elay t est c ircuit y z d di r l 54? c l 50pf 3.3v v od f igure 7. d river p ropagation d elay t iming d iagram vcc 0v di y z v o + v diff v y C v z 0v v o C vcc/2 vcc/2 t plh t f t r v o 1/2v o 1/2v o t phl t skew = |t dplh - t dphl | t dplh t dphl 10% 90% 10% 90% f igure 8. d river e nable and d isable t ime t est c ircuit 1 generator 50? s1 r l = 500? out c l = 50pf d 0 or vcc z y di xr3170e-3178e 11 rev. 1.0.0 3.3v high speed rs-485/rs- 422 transceivers with 1/8 th unit load
f igure 9. d river e nable d isable t iming d iagram 1 de out vcc/2 t zh , t zh(shdn) v om = (v ol + vcc)/2 t hz 0.25v vcc 0 0 f igure 10. d river e nable and d isable t ime t est c ircuit 2 generator 50? s1 r l = 500? out c l = 50pf d 0 or vcc z y di vcc xr3170e-3178e 12 3.3v high speed rs-485/rs-422 transceivers with 1/8 th unit load rev. 1.0.0
f igure 11. d river e nable and d isable t iming d iagram 2 de out vcc/2 t zl , t zl(shdn) v om = (v ol + vcc)/2 t lz 0.25v vcc 0 v ol f igure 12. r eceiver p ropagation d elay t est c ircuit out r a b v id re c l 15pf f igure 13. r eceiver p ropagation d elay t iming d iagram b a out t phl t plh +1v -1v v oh v ol 1.5v xr3170e-3178e 13 rev. 1.0.0 3.3v high speed rs-485/rs- 422 transceivers with 1/8 th unit load
f igure 14. r eceiver e nable and d isable t imes t est c ircuit 1.5v -1.5v s3 a generator 50? c l = 15pf r 1k? s1 s2 vcc b re f igure 15. r eceiver e nable and d isable t iming d iagram 1 3v 1.5v 0v re out s1 is open, s2 is closed, s3 = 1.5v v oh t zh, t zh(shdn) v oh /2 f igure 16. r eceiver e nable and d isable t iming d iagram 2 3v 0v 1.5v v cc re out s1 is closed, s2 is open, s3 = -1.5v t zl, t zl(shdn) v o l = v cc /2 v ol xr3170e-3178e 14 3.3v high speed rs-485/rs-422 transceivers with 1/8 th unit load rev. 1.0.0
f igure 17. r eceiver e nable and d isable t iming d iagram 3 3v 1.5v 0v re out s1 is open, s2 is closed, s3 = 1.5v v oh t hz 0.25v f igure 18. r eceiver e nable and d isable t iming d iagram 4 3v 0v 1.5v v cc re out s1 is closed, s2 is open, s3 = -1.5v t lz v ol 0.25v xr3170e-3178e 15 rev. 1.0.0 3.3v high speed rs-485/rs- 422 transceivers with 1/8 th unit load
xr3170e-3178e 16 3.3v high speed rs-485/rs-422 transceivers with 1/8 th unit load rev. 1.0.0 1.0 product description xr3170e-xr3178e is a family of adv anced rs-485/rs-422 transceivers. each contains one driver and one receiver. all devices operate from a single +3.3v supply. the xr3172e, xr3175e and xr3178e are a half- duplex design while the other devices are full-duplex designs. the control pins re and de feature a hotswap capability allowing live insertion without spurious data transfer. drivers are output short-circuit current limited. thermal-shutdown circuitry protects drivers against exce ssive power dissipation. when activited, the thermal- shutdown circuitry forces the driver outptus into a high-impedance state. advanced failsafe ordinary rs-485 differential receiver s will be in an indetermin ate state whenever the data bus is not being actively driven. the advanced failsaf e feature of the xr3170e family guar antees 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. in a terminated bus with all tr ansmitters disabled, the receivers? differential input voltage is pulled to 0v by the termination. the xr3170e family interprets 0v differential as a logic high with a minimum 50mv noise margin while maintaining compliance with the ei a/tia-485 standard of +/-200mv. receiver input filtering xr3170e-xr3175e receivers incorpoprate input filtering in ad dition to input hysteresis. this filtering enhances noise immunity with differential signals that have very slow rise and fall times. receiver propagation delay increases slightly due to this filter ing. xr3176e, xr3177e abd xr3178e hi gh speed devices do not have this input filtering. hot-swap capability when vcc is first applied the xr3170e family holds the d river enable and receiver enable inactive for approximately 10 microseconds. during power ramp-up other system ic?s may drive unpredictable values. hot-swap capability prevents the xr3170e family from driving any output signal until power has stabilized. after the initial power-up sequence, the hot-swap circui t becomes transparent and driver enable and receiver enable resume their normal functions and timings. if circuit boards are inserted into an energized backpl ane (commonly called "live insertion" or "hot-swap") power may suddenly be applied to all circuits. without the hot-swap capability, this situat ion could improperly enable the transceiver?s driver or rece iver, driving invalid data onto shared busses and possibly causing driver contention or device damage. +/-15kv esd protection esd protection structures are incorporated on all pins to pr otect against electros tatic discharges encountered during handling and assembly. the driver outputs and receiver inputs of the xr3170e family have extra protection against static electricity. exar uses state of the art structures to protect these pins against esd of +/-15kv without damage. the esd struct ures withstand high esd in all states: normal operation, shutdown and powered down. after an esd event, the xr3170e-xr3178e keep operating without latch-up or damage. esd protection can be tested in various ways. the tran smitte r outputs and receiver inputs of the xr3170e- xr3178e are characterized for protection to the following limits: +/-15kv using the human body model +/-8kv using the contact discharge model +/-15kv air-gap discharge model esd test conditions esd performance depends on a variety of conditions. contact exar for a re liability report that documents test setup, methodology and results.
xr3170e-3178e 17 rev. 1.0.0 3.3v high speed rs-485/rs- 422 transceivers with 1/8 th unit load iec 61000-4-2 the iec 61000-4-2 standard covers esd testing and perform ance of finished equipment. however, it does not specifically refer to integrated circuits. the xr 3170e family helps you design equipment to meet iec 61000-4-2, without sacrificing board-space and cost for external esd-protection components. the major differences between tests done using the hu ma n body model and iec 61000-4-2 is a higher peak current in iec 61000-4-2. series resistance is lower in the iec 61000-4-2 model. hence, the esd withstand voltage measured to iec 61000-4-2 is genera lly lower than that of human body model. the air-gap test involves approaching the device with a charged probe. the contact discharge method con nects the probe to the device before the probe is energized. machine model the machine model for esd tests all pins using a 200pf storage capacitor and zero discharge resistance. the o bjective is to emulate the stress caused when i/o pins are contacted by handling equipment during test and assembly. 256 transceivers on the bus the standard rs-485 receiver input impedance is 12k ohms (1 unit load). a standard driver can drive up to 32 u nit loads. the xr3170e family of transceivers have only a 1/8 th unit load receiver input impedance of 96k ohms, thereby allowing eight times as many, up to 256, transceivers to be connected in parallel on a communication line. any combination of these devices and other rs-485 transceivers up to a total of 32 unit loads may be connected to the line. low power shutdown mode low-power shutdown mode is initiated by bringing both re high and de low simultaneously. while in shutdown devices draw less than 1 a of supply current. de and re may be tied together and driven by a single control signal. devices are guaranteed not to enter shutdown if re is high and de is low for less than 50ns. if the inputs are in this state for at leas t 600ns, the parts will enter shutdown. enable times t zh and t zl apply when the part is not in low-power shutdown state. enable times t zh(shdn) and t zl(shdn) apply when the parts are shutdown. the drivers and receivers take longer to become enabled from low-power shutdown t zh(shdn) and t zl(shdn) than from driver / receiver disable mode ( t zh and t zl ). driver output protection two mechanisms prevent excessive output current and power dissipation caused by faults or by bus contention. first, a driver current limit on the output stage provides immediate protection against short circuits over the whole common-mode voltage range. second, a the rmal-shutdown circuit forces the driver outputs into a high-impedance state if junction temperature becomes excessive. line length the rs-485/rs-422 standard covers line lengths up to 40 00f t. maximum achievable line length is a function of signal attenuation and noise. termination prevents sign al reflections by eliminating the impedance mismatches on a transmission line. line termination is generaly used if rise and fall times are shorter than the round-trip signal propagation time
xr3170e-3178e 18 3.3v high speed rs-485/rs-422 transceivers with 1/8 th unit load rev. 1.0.0 2.0 function tables t able 1: full duplex 14 pin - xr3170e, xr3173e and xr3176e inputs outputs re de di y z x 1 1 1 0 x 1 0 0 1 0 0 x high-z 1 0 x shutdown t able 2: full duplex 8 pi n - xr3171e, xr3174e and xr3177e input outputs di y z 1 1 0 0 0 1 t able 3: half duplex 8 pin - xr3172e, xr2175e and xr3178e inputs outputs re de di a b x 1 1 1 0 x 1 0 0 1 0 0 x high-z 1 0 x shutdown transmitting transmitting transmitting
t able 4: full duplex 14 pin - xr3170e, xr3173e and xr3176e inputs ouptut re de v - v ro 0 x -50mv 1 0 x -200mv 0 0 x open/shorted 1 1 1 x high-z 1 0 x shutdown t able 5: full duplex 8 pi n - xr3171e, xr3174e and xr3177e inputs output v - v ro -50m v 1 -200mv 0 open/shorted 1 t able 6: half duplex 8 pin - xr3172e, xr2175e and xr3178e inputs output re de v - v ro 0 x -50mv 1 0 x -200mv 0 0 x open/shorted 1 1 1 x high-z 1 0 x shutdown xr3170e-3178e 19 rev. 1.0.0 3.3v high speed rs-485/rs- 422 transceivers with 1/8 th unit load note: receiver inputs -200mv < v a - v b < -50mv should be considered indeterminate. receiving a b receiving a b receiving a b
xr3170e-3178e 20 3.3v high speed rs-485/rs-422 transceivers with 1/8 th unit load rev. 1.0.0 3.0 product selector guide t able 7: selection guide bps xr3170e full 250k yes yes 256 sn75180 xr3171e full 250k no no 256 sn75179 xr3172e half 250k yes yes 256 sn75176 xr3173e full 500k yes yes 256 sn75180 xr3174e full 500k no no 256 sn75179 xr3175e half 500k yes yes 256 sn75176 xr3176e full 20m yes yes 256 sn75180 xr3177e full 20m no no 256 sn75179 xr3178e half 20m yes yes 256 sn75176 part number duplex data rate shutdown receiver a nd driver enable trans on bus foot-print
xr3170e-3178e 21 rev. 1.0.0 3.3v high speed rs-485/rs- 422 transceivers with 1/8 th unit load 4.0 typical applications: r t r t stub half-duplex network bi-directional full-duplex network repeater (optional) repeater (optional) point to multi-point with repeater
package dimensions (14 pin nsoic) xr3170e-3178e 22 3.3v high speed rs-485/rs-422 transceivers with 1/8 th unit load rev. 1.0.0
package dimensions (8 pin nsoic) xr3170e-3178e 23 rev. 1.0.0 3.3v high speed rs-485/rs- 422 transceivers with 1/8 th unit load
revision history d ate r evision d escription 12/03/09 1.0.0 production release. 24 notice exar corporation reserves the right to make changes to the products contained in this publicat ion in order to improve design, performanc e or reliability. exar corp oration assumes no responsibility for the use of any circuits described herein, conveys no license under any patent or other right, and makes no representation that the circuits are free of patent infr ingement. charts and schedules contai ned here in are only for illustration purposes and may vary depending upon a user?s specific application. while the information in this publication has been carefully ch ecked; no responsibility, however , is assumed for inaccuracies. exar corporation does not re commend the use of any of its products in life suppo rt applications where the failure or malfunction of the product can reasonably be ex pected to cause failure of the life support system or to significantly affect its safety or effectiveness. products ar e not authorized for use in such applications unless exar corporation receives , in writing, assuranc es to its satisfaction that: (a) th e risk of injury or damage has been minimized; (b) th e user assumes all such ris ks; (c) potential liability of exar corporation is adequately protected under the circumstances. copyright 2009 exar corporation datasheet december 2009. send your uart technical inquiry with technical details to hotline: uarttechsupport@exar.com . reproduction, in part or whole, without the prior written consent of exar co rporation is prohibited. xr3170e-3178e 3.3v high speed rs-485/rs-422 transceivers with 1/8 th unit load rev. 1.0.0

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