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________________________________________________________________________ http://www.union-ic.com rev.02 jun.2012 1/14 um3491 +3.3v low power 15kv esd-protected, fail- safe, rs-422 transceivers in sop14/dip14 general description the um3491 is 15kv electrostatic discharge (esd)-protected, high-speed transceivers for rs-422 communication that contain one driver and one receiver. the device features fail-safe circuitry, which guarantees a logic-high receiver output when the receiver inputs are open or shorted. this means that the receiver output will be a logic high if all transmitters on a terminated bus are disabled (high impedance). the um 3491 allowing transmit speeds up to 10mbps. the device features enhanced esd protection. all transmitter outputs and receiver inputs are protected to 15kv using the human body model. these transceivers typically draw 180 a of supply current when unloaded, or when fully loaded with the dri vers disabled. the device has a 1/8-unit-load receiver input impe dance that allows up to 256 transceivers on the bus. the um3491 is intended for full-duplex communications. applications features z rs-422 communications z level translators z transceivers for emi-sensitive applications z industrial-control local area networks z esd protection for rs-422 i/o pins 15kv, human body model z true fail-safe receiv er while maintaining eia/tia-422 compatibility z maximum data rate up to 10mbps z error-free data transmission z 1na low-current shutdown mode z allow up to 256 transceivers on the bus pin configurations top view xx: week code um3491eese sop14 xx: week code UM3491EEPE dip14 selector guide part number half/full duplex data rate (mbps) slew- rate limited low- power shutdown receiver/ driver enable quiescent current ( a) transceivers on bus pin count um3491 full 10 yes yes yes 180 256 14 1 2 3 4 5 6 7 8 9 10 11 12 13 14 r d nc ro re de di gnd gnd vcc nc a b z y nc
________________________________________________________________________ http://www.union-ic.com rev.02 jun.2012 2/14 um3491 ordering information part number temperature range packaging type shipping qty um3491eese -40c to +85c sop14 2500pcs/13 inch tape & reel UM3491EEPE -40c to +85c dip14 25pcs tube absolute maximum ratings symbol parameter value unit v cc supply voltage +7 v control input voltage (re, de) -0.3v to (vcc + 0.3v) v driver input voltage (di) -0.3v to (vcc + 0.3v) v driver output voltage (a, b, y, z) 13 v receiver input voltage (a, b) 25 v receiver output voltage (ro) -0.3v to (vcc + 0.3v) v 14-pin plastic dip (derate 10.0mw/c above +70c) 800 p d 14-pin so (derate 8.33mw/c above +70c) 667 mw t a ambient temperature -40 to +85 c t stg storage temperature range -65 to +150 c t l lead temperature for sold ering 10 seconds +300 c dc electrical characteristics (v cc = +3.3v 5%, t a = t min to t max , unless otherwise noted. typical values are at v cc = +3.3v and t a = +25c.) (note 1) parameter symbol test conditions min typ max unit driver differential driver output (no load) v od1 figure 3 vcc v differential driver output v od2 figure 3 , r = 50 ? 1.8 vcc v differential driver output v od3 figure 3 , r = 27 ? 1.3 vcc v change-in-magnitude of differential output voltage (note 2) v od figure 3 , r = 50 ? 0.2 v driver common-mode output voltage v oc figure 3 , r = 50 ? 3.0 v input high voltage v ih de, di, re ______ 2.0 v input low voltage v il de, di, re ______ 0.8 v di input hysteresis v hys 100 mv
________________________________________________________________________ http://www.union-ic.com rev.02 jun.2012 3/14 um3491 dc electrical characteristics (continued) (v cc = +3.3v 5%, t a = t min to t max , unless otherwise noted. typical values are at v cc = +3.3v and t a = +25c.) (note 1) parameter symbol test conditions min typ max unit driver -7v v out v cc -250 driver short-circuit output current (note 3) v od1 0v v out 12v 250 ma receiver v in = 12v 125 a input current (a and b) i in de = gnd, v cc = gnd or 3.465v v in = -7v -75 receiver differential threshold voltage v th -7v v cm 12v -200 -125 -50 mv receiver input hysteresis v th 25 mv receiver output high voltage v oh i o = -4ma, v id = -50mv vcc -0.4 v receiver output low voltage v ol i o = 4ma, v id = -200mv 0.4 v three-state output current at receiver i ozr 0.4v v o 2.4v 1 a receiver input resistance r in -7v v cm 12v 96 k ? receiver output short circuit current i osr 0v v ro v cc 7 95 ma supply current re = v cc 20 60 supply current i cc no load, de =di=gnd or v cc re = gnd 180 300 a supply current in shutdown mode i shdn de = gnd, v re = v cc 0.001 10 a esd protection for y, z, a, b human body model 15 kv note 1: all currents into the device are positive; all currents out of the device are negative. all voltages are referred to device ground unless otherwise noted. note 2: v od and v oc are the changes in v od and v oc , respectively, when the di input changes state. note 3: maximum current level applies to peak current just prior to foldback-current limiting; minimum current level applies during current limiting.
________________________________________________________________________ http://www.union-ic.com rev.02 jun.2012 4/14 um3491 switching characteristics (v cc = +3.3v 5%, t a = t min to t max , unless otherwise noted. typical values are at v cc = +3.3v and t a = +25c.) parameter symbol test conditions min typ max unit t dplh 10 30 60 driver input-to-output t dphl figures 5 and 7 , r diff = 54 ? , c l1 = c l2 = 100pf 10 30 60 ns driver output skew | t dplh - t dph l | t dskew figures 5 and 7 , r diff = 54 ? , c l1 = c l2 = 100pf 10 25 ns driver rise or fall time t dr , t df figures 5 and 7 , r diff = 54 ? , c l1 = c l2 = 100pf 5 15 30 ns maximum data rate f max 10 mbps driver enable to output high t dzh figures 6 and 8 , c l = 100pf, s2 closed 40 70 ns driver enable to output low t dzl figures 6 and 8 , c l = 100pf, s1 closed 40 70 ns driver disable time from low t dlz figures 6 and 8 , c l = 15pf, s1 closed 40 70 ns driver disable time from high t dhz figures 6 and 8 , c l = 15pf, s2 closed 40 70 ns receiver input to output t rplh , t rphl figures 9 and 11; | v id | 2.0v; rise and fall time of v id 1 5ns 20 100 180 ns | t rplh - t rphl | differential receiver skew t rskd figures 9 and 11; | v id | 2.0v; rise and fall time of v id 1 5ns 13 ns receiver enable to output low t rzl figures 4 and 10, c l = 100pf, s1 closed 40 100 ns receiver enable to output high t rzh figures 4 and 10, c l = 100pf, s2 closed 40 100 ns receiver disable time from low t rlz figures 4 and 10, c l = 100pf, s1 closed 40 100 ns receiver disable time from high t rhz figures 4 and 10, c l = 100pf, s2 closed 40 100 ns time to shutdown t shdn (note 4 ) 50 200 600 ns driver enable from shutdown to output high t dzh(shdn ) figures 6 and 8 , c l = 15pf, s2 closed 40 200 ns driver enable from shutdown to output low t dzl(shdn ) figures 6 and 8 , c l = 15pf, s1 closed 40 200 ns receiver enable from shutdown- to-output high t rzh(shdn ) figures 4 and 10, c l = 100pf, s2 closed 150 500 ns receiver enable from shutdown- to-output low t rzl(shdn) figures 4 and 10, c l = 100pf, s1 closed 150 500 ns note 4 : the device is put into shutdown by bringing re _______ high and de low. if the enable inputs are in this state for less than 50ns, the device is guaranteed not to enter shutdown. if the enable inputs are in this state for at least 600ns, the device is guaranteed to have entered shutdown.
________________________________________________________________________ http://www.union-ic.com rev.02 jun.2012 5/14 um3491 typical operating characteristics (v cc = +3.3v, t a = +25c, unless otherwise noted.) no load supply current vs. temperature 100 125 150 175 200 225 250 -60 -40 -20 0 20 40 60 80 100 temperature( ) no load supply current( a) re=l,de=h output current vs.receiver output high voltage 0 5 10 15 20 25 30 01234 output high voltage (v) output current ( a) output current vs. receiver output low voltage 0 10 20 30 40 50 60 01234 output low voltage (v) output current ( a) receiver output high voltage vs. temperature 2.5 2.55 2.6 2.65 2.7 2.75 2.8 2.85 2.9 2.95 3 -60 -40 -20 0 20 40 60 80 100 temperature( ) receiver output high voltage(v) i ro =8ma
________________________________________________________________________ http://www.union-ic.com rev.02 jun.2012 6/14 um3491 typical operating characteristics (continued) (v cc = +3.3v, t a = +25c, unless otherwise noted.) receiver output low voltage vs. temperature 0.1 0.15 0.2 0.25 0.3 0.35 0.4 -60 -40 -20 0 20 40 60 80 100 temperature( ) receiver output low voltage(v) i ro =8ma driver differential output voltage vs. temperature 1 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2 -60 -40 -20 0 20 40 60 80 100 temperature( ) output voltage(v) r t =54ohm driver output current vs.differential output voltage 0.1 1 10 100 00.511.522.533.5 differential output voltage (v) output current (ma)
________________________________________________________________________ http://www.union-ic.com rev.02 jun.2012 7/14 um3491 pin description pin number symbol function 1 nc not connected 2 ro receiver output. when r e ________ is low and if a - b -50mv, ro will be high; if a - b -200mv, ro will be low. 3 re _______ receiver output enable. drive re ______ low to enable ro; ro is high impedance when re ______ is high. drive re ______ high and de low to enter low-power shutdown mode. 4 de driver output enable. drive de high to enable driver outputs. these outputs are high impedance when de is low. drive re ______ high and de low to enter low-power shutdown mode. 5 di driver input. with de high, a low on di forces non-inverting output low and inverting output high. similarly, a high on di forces non-inverting output high and inverting output low. 6 gnd ground 7 gnd ground 8 nc not connected 9 y non-inverting driver output 10 z inverting driver output 11 b inverting receiver input 12 a non-inverting receiver input 13 nc not connected 14 vcc positive supply 3.135v v cc 3.465v functions tables transmitting inputs outputs re ______ de di z y x 1 1 0 1 x 1 0 1 0 0 0 x high-z high-z 1 0 x shutdown receiving inputs output re ______ de a-b ro 0 x -0.05v 1 0 x -0.2v 0 0 x open/short 1 1 1 x high-z 1 0 x shutdown
________________________________________________________________________ http://www.union-ic.com rev.02 jun.2012 8/14 um3491 typical operating circuit figure 1: um3491 pin configuration and typical full-duplex operating circuit r d r d ro re de di a b z y 120ohm 120ohm di de re ro yzb a r d di de re ro yzb a 120ohm 120ohm d r a b z y di de re ro figure 2: typical full-duplex rs-422 network
________________________________________________________________________ http://www.union-ic.com rev.02 jun.2012 9/14 um3491 detailed description the um3491 high-speed transceivers for rs-422 communication contain one driver and one receiver. the device features fail-safe circuitry, which guarantees a logic-high receiver output when the receiver inputs are open or shorted, or when they are connected to a terminated transmission line with all drivers disabled. the um3491 offer higher driver output slew-rate limits, allowing transmit speeds up to 10mbps. the um3491 is full-duplex transceiver. it operat es from a single +3.3v supply. drivers are output short-circuit current limited. thermal shutdown ci rcuitry protects drivers against excessive power dissipation. when activated, the thermal shutdown circuitry places the driver outputs into a high- impedance state. receiver input filtering the receivers of the um3491 incorporate input filtering in addition to input hysteresis. this filtering enhances noise immunity with differential si gnals that have very slow rise and fall times. receiver propagation delay increases by 20% due to this filtering. fail-safe the um3491 guarantees a logic-high receiver output when the receiver inputs are shorted or open, or when they are connected to a terminated tran smission line with all drivers disabled. this is done by setting the receiver threshold between - 50mv and -200mv. if the differential receiver input voltage (a-b) is greater than or equal to -50mv, ro is logic high. if a-b is less than or equal to -200mv, ro is logic low. in the case of a terminated bus with all transmitters disabled, the receiver?s differential input voltage is pulled to 0v by the termination. with the receiver thresholds of the um3491, this results in a logic high with a 50mv minimum noise margin. unlike previous fail-safe devices, the -50mv to -200mv threshold complies with the 200mv eia/tia-422 standard. 15kv esd protection as with all union devices, esd-protection structures are incorporated on all pins to protect against electrostatic discharges encountered dur ing handling and assembly. the driver outputs and receiver inputs of the um3491 have extra protectio n against static electricity. union?s engineers have developed state-of-the-art structures to protect these pins against esd of 15kv without damage. the esd-protected pins are test ed with reference to the ground pin in a powered-down condition. they are tested to 15kv using the human body model.
________________________________________________________________________ http://www.union-ic.com rev.02 jun.2012 10/14 um3491 test circuit figure 3. driver dc test load figu re 4. receiver enable/disable timing test load figure 5. driver timing test circuit figure 6. driver enable and disable timing test load figure 7. driver propagation delays figure 8. driver enable and disable times figure 9. receiver propagation delays figure 10. receiver enable and disable times figure 11. receiver propagation delay test circuit figure 12: line repeater y z r r v od v oc 1k 1k vcc s1 s2 + c rl 15pf test point receive output z y di de 3v v od2 c l1 c l2 r diff + c l s1 s2 vcc output under test 500ohm di 0v 3.3v 1.5v z y v o 1/2v o t dphl 1/2v o 1.5v t dplh v diff 0 v o v o 10 90 10 90 t dr t df v diff =v(y)-v(z) t skew =t dplh - t dphl 1.5v 1.5v de 0v 3.3v y,z y,z 0 v ol v ol +0.5v v oh- 0.5v 2.3v 2.3v output normally low output normally high t dzl(shdn), tdzl t dzh(shdn), tdzh tdhz tdlz 1.5v 1.5v input a b 1v -1v v oh v ol ro output t rplh t rphl 1.5v 1.5v re 0v 3.3v ro 0 vcc v ol +0.5v v oh- 0.5v 1.5v 1.5v output normally low output normally high t rzl(shdn), trzl t rzh(shdn), trzh trhz trlz ate v d r b a receiver output 120ohm di ro r d y z b a 120ohm data in data out re de
________________________________________________________________________ http://www.union-ic.com rev.02 jun.2012 11/14 um3491 applications information 256 transceivers on the bus the standard rs-422 receiver input impedance is 12k ? (one-unit load), and the standard driver can drive up to 32 unit loads. the um3491 has a 1/8-unit-load receiver input impedance (96k ? ), allowing up to 256 transceivers to be connect ed in parallel on one communication line. any combination of these devices and/or other rs-422 tr ansceivers with a total of 32 unit loads or less can be connected to the line. reduced emi and reflections the um3491 is slew-rate limited, minimizing em i and reducing reflections caused by improperly terminated cables. it?s high-frequency harmonic components are much lower in amplitude, and the potential for emi is significantly reduced. in general, a transmitter?s rise time relates direc tly to the length of an unterminated stub, which can be driven with only minor waveform reflections. the following equation expresses this relationship conservatively: length = t rise / (10 1.5ns/ft) where t rise is the transmitter?s rise time. low-power shutdown mode low-power shutdown mode is initiated by bringing both re _____ high and de low. in shutdown, the devices typically draw only 1na of supply current. re _____ and de may be driven simultaneously; the parts 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 least 600ns , the parts are guaranteed to enter shutdown. enable times t zh and t zl in the switching characteristics tables assume the part was not in a low-power shutdown state. enable times t zh(shdn) and t zl(shdn) assume the parts were shut down. it takes drivers and receivers longer to become enabled from low-power shutdown mode (t zh(shdn) , t zh(shdn) ) than from driver/receiver-disable mode (t zh , t zl ). driver output protection two mechanisms prevent excessive output current and power dissipation caused by faults or by bus contention. the first, a foldback current limit on the output stage, provides immediate protection against short circuits over the whol e common-mode voltage range. the second, a ther- mal shutdown circuit, forces the driver outputs into a high-impedance state if the die temperature becomes excessive. line length vs. data rate the rs-422 standard covers line lengths up to 400 0 feet. for line lengths greater than 4000 feet, use the repeater application shown in figure 12.
________________________________________________________________________ http://www.union-ic.com rev.02 jun.2012 12/14 um3491 package information um3491eese sop14 outline drawing dimensions millimeters inches symbol min max min max a 1.35 1.75 0.053 0.069 a1 0.10 0.25 0.004 0.010 b 0.35 0.49 0.014 0.019 c 0.19 0.25 0.007 0.010 e 3.80 4.00 0.150 0.157 d 8.55 8.75 0.337 0.344 e 1.27 0.050 h 5.80 6.20 0.228 0.244 l 0.40 1.27 0.016 0.050 land pattern notes: 1. compound dimension: 8.653.90 2. unit: mm; 3. general tolerance 0.05mm unless otherwise specified; 4. the layout is just for reference. tape and reel orientation
________________________________________________________________________ http://www.union-ic.com rev.02 jun.2012 13/14 um3491 um391eepe dip14 outline drawing dimensions millimeters inches symbol min max min max a - 5.08 - 0.200 a1 0.38 - 0.015 - a2 3.18 4.45 0.125 0.175 a3 1.40 2.03 0.055 0.080 b 0.41 0.56 0.016 0.022 b1 1.14 1.65 0.045 0.065 c 0.20 0.30 0.008 0.012 d 18.67 19.43 0.735 0.765 d1 0.13 2.03 0.005 0.080 e 7.62 8.26 0.300 0.325 e1 6.10 7.87 0.240 0.310 e 2.54 - 0.100 - ea 7.62 - 0.300 - eb - 10.16 - 0.400 l 2.92 3.81 0.115 0.150
________________________________________________________________________ http://www.union-ic.com rev.02 jun.2012 14/14 um3491 important notice the information in this document has been ca refully reviewed and is believed to be accurate. nonetheless, this document is subjec t to change without notice. union assumes no responsibility for any inaccuracies that may be contained in this document, and makes no commitment to update or to keep current the contained information, or to notify a person or organization of any update. union rese rves the right to make changes, at any time, in order to improve reliability, function or design and to attempt to supply the best product possible. union semiconductor, inc add: 7f, no. 5, bibo road, shanghai 201203 tel: 021-51097928 fax: 021-51026018 website: www.union-ic.com

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