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1 ltc1334 single 5v rs232/rs485 multiprotocol transceiver the ltc ? 1334 is a low power cmos bidirectional trans- ceiver featuring two reconfigurable interface ports. it can be configured as two rs485 differential ports, as two dual rs232 single-ended ports or as one rs485 differential port and one dual rs232 single-ended port. an onboard charge pump requires four 0.1 m f capacitors to generate boosted positive and negative supplies, allowing the rs232 drivers to meet the rs232 5v output swing requirement with only a single 5v supply. a shutdown mode reduces the i cc supply current to 10 m a. the rs232 transceivers are in full compliance with rs232 specifications. the rs485 transceivers are in full compli- ance with rs485 and rs422 specifications. all interface drivers feature short-circuit and thermal shutdown pro- tection. an enable pin allows rs485 driver outputs to be forced into high impedance, which is maintained even when the outputs are forced beyond supply rails or power is off. both driver outputs and receiver inputs feature 10kv esd protection. a loopback mode allows the driver outputs to be connected back to the receiver inputs for diagnostic self-test. n four rs232 transceivers or two rs485 transceivers on one chip n operates from a single 5v supply n withstands repeated 10kv esd pulses n uses small charge pump capacitors: 0.1 m f n low supply current: 8ma typical n 10 m a supply current in shutdown n self-testing capability in loopback mode n power-up/down glitch-free outputs n driver maintains high impedance in three-state, shutdown or with power off n thermal shutdown protection n receiver inputs can withstand 25v n low power rs485/rs422/rs232/eia562 interface n software-selectable multiprotocol interface port n cable repeaters n level translators , ltc and lt are registered trademarks of linear technology corporation. 21 5v 8 5v 9 5v 20 0v 26 3 26 3 27 28 v cc1 5v 120 w 4 ltc1334 ltc1334 ?ta01 rx out 23 rs485 interface dr enable 5 6 7 14 24 dr in 22 15 13 21 ltc1334 rx out 18 5v dr enable 12 11 10 9 8 14 17 dr in 19 5v 20 15 120 w 4000-ft 24-gauge twisted pair 5v 0v 11 dr in 19 4 24 rx out 12 16 rx out 7 dr in 23 rs232 interface all capacitors: 0.1 m f monolithic ceramic type 10 dr in 18 5 25 rx out 13 17 rx out 6 dr in 22 1 2 2 1 28 27 v cc2 5v descriptio u features applicatio s u typical applicatio u
2 ltc1334 a u g w a w u w a r b s o lu t exi t i s order part number ltc1334cg ltc1334cnw ltc1334csw ltc1334ig ltc1334isw (note 1) supply voltage (v cc ) ............................................. 6.5v input voltage drivers ................................... C 0.3v to (v cc + 0.3v) receivers ............................................. C 25v to 25v on/off, lb, sel1, sel2 ........ C 0.3v to (v cc + 0.3v) output voltage drivers ................................................. C 18v to 18v receivers ............................... C 0.3v to (v cc + 0.3v) short-circuit duration output ........................................................ indefinite v dd , v ee , c1 + , c1 C , c2 + , c2 C .......................... 30 sec operating temperature range commercial ........................................... 0 c to 70 c industrial ............................................ C 40 c to 85 c storage temperature range ................ C 65 c to 150 c lead temperature (soldering, 10 sec)................ 300 c wu u package / o rder i for atio t jmax = 125 c, q ja = 90 c/w (g) t jmax = 125 c, q ja = 56 c/w (nw) t jmax = 125 c, q ja = 85 c/w (sw) 1 2 3 4 5 6 7 8 9 10 11 12 13 14 top view 28 27 26 25 24 23 22 21 20 19 18 17 16 15 c2 + c2 v cc r b1 r a1 d z1 /de1 d y1 lb on/off d y2 d z2 /de2 r a2 r b2 v ee c1 + c1 v dd a1 b1 y1 z1 sel1 sel2 z2 y2 b2 a2 gnd sw package 28-lead plastic so wide g package 28-lead plastic ssop nw package 28-lead pdip wide consult factory for military grade parts. dc electrical characteristics symbol parameter conditions min typ max units rs485 driver (sel1 = sel2 = high) v od1 differential driver output voltage (unloaded) i o = 0 l 6v v od2 differential driver output voltage (with load) figure 1, r = 50 w (rs422) l 2.0 6 v figure 1, r = 27 w (rs485) l 1.5 6 v d v od change in magnitude of driver differential figure 1, r = 27 w or r = 50 w l 0.2 v output voltage for complementary output states v oc driver common mode output voltage figure 1, r = 27 w or r = 50 w l 3v d? v oc ? change in magnitude of driver common mode figure 1, r = 27 w or r = 50 w l 0.2 v output voltage for complementary output states i osd driver short-circuit current C 7v v o 12v, v o = high l 35 250 ma C 7v v o 12v, v o = low (note 4) l 10 250 ma i ozd three-state output current (y, z) C 7v v o 12v l 5 500 m a rs232 driver (sel1 = sel2 = low) v o output voltage swing figure 4, r l = 3k, positive l 5 6.5 v figure 4, r l = 3k, negative l C5 C6.5 v i osd output short-circuit current v o = 0v l 60 ma driver inputs and control inputs v ih input high voltage d, de, on/off, sel1, sel2, lb l 2v v il input low voltage d, de, on/off, sel1, sel2, lb l 0.8 v i in input current d, sel1, sel2 l 10 m a de, on/off, lb l C4 C15 m a the l denotes specifications which apply over the full operating temperature range, otherwise specifications are at t a = 25 c. v cc = 5v, c1 = c2 = c3 = c4 = 0.1 m f (notes 2, 3)
3 ltc1334 ac electrical characteristics symbol parameter conditions min typ max units rs485 receiver (sel1 = sel2 = high) v th differential input threshold voltage C 7v v cm 12v, ltc1334c l C 0.2 0.2 v C7v v cm 7v, ltc1334i l C0.3 0.3 v d v th input hysteresis v cm = 0v 70 mv i in input current (a, b) v in = C 7v l C 0.8 ma v in = 12v l 1.0 ma r in input resistance C 7v v in 12v l 12 24 k w rs232 receiver (sel1 = sel2 = low) v th receiver input threshold voltage input low threshold l 0.8 v input high threshold l 2.4 v d v th receiver input hysteresis 0.6 v r in receiver input resistance v in = 10v 3 5 7 k w receiver output v oh receiver output high voltage i o = C 3ma, v in = 0v, sel1 = sel2 = low l 3.5 4.6 v v ol receiver output low voltage i o = 3ma, v in = 3v, sel1 = sel2 = low l 0.2 0.4 v i osr short-circuit current 0v v o v cc l 785ma i ozr three-state output current on/off = low l 10 m a r ob inactive b output pull-up resistance (note 5) on/off = high, sel1 = sel2 = high 50 k w power supply generator v dd v dd output voltage no load, on/off = high 8.5 v i dd = C 10ma, on/off = high 7.6 v v ee v ee output voltage no load, on/off = high C 7.7 v i ee = 10ma, on/off = high C 6.9 v power supply i cc v cc supply current no load, sel1 = sel2 = high l 825 ma no load shutdown, on/off = 0v l 10 100 m a symbol parameter conditions min typ max units rs232 mode (sel1 = sel2 = low) sr slew rate figure 4, r l = 3k, c l = 15pf l 30 v/ m s figure 4, r l = 3k, c l = 1000pf l 4v/ m s t t transition time figure 4, r l = 3k, c l = 2500pf l 0.22 1.9 3.1 m s t plh driver input to output figures 4, 9, r l = 3k, c l = 15pf l 0.6 4 m s t phl driver input to output figures 4, 9, r l = 3k, c l = 15pf l 0.6 4 m s t plh receiver input to output figures 5, 10 l 0.3 6 m s t phl receiver input to output figures 5, 10 l 0.4 6 m s rs485 mode (sel1 = sel2 = high) t plh driver input to output figures 2, 6, r l = 54 w , c l = 100pf l 20 40 70 ns t phl driver input to output figures 2, 6, r l = 54 w , c l = 100pf l 20 40 70 ns t skew driver output to output figures 2, 6, r l = 54 w , c l = 100pf l 515 ns t r , t f driver rise and fall time figures 2, 6, r l = 54 w , c l = 100pf l 31540 ns dc electrical characteristics the l denotes specifications which apply over the full operating temperature range, otherwise specifications are at t a = 25 c. v cc = 5v, c1 = c2 = c3 = c4 = 0.1 m f (notes 2, 3) the l denotes specifications which apply over the full operating temperature range, otherwise specifications are at t a = 25 c. v cc = 5v, c1 = c2 = c3 = c4 = 0.1 m f (notes 2, 3)
4 ltc1334 ac electrical characteristics note 1: absolute maximum ratings are those values beyond which the safety of the device cannot be guaranteed. 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: all typicals are given at v cc = 5v, c1 = c2 = c3 = c4 = 0.1 m f and t a = 25 c. note 4: short-circuit current for rs485 driver output low state folds back above v cc . peak current occurs around v o = 3v. note 5: the b rs232 receiver output is disabled in rs485 mode (sel1 = sel2 = high). the unused output driver goes into a high impedance mode and has a resistor to v cc . see applications information section for more details. typical perfor m a n ce characteristics u w receiver output high voltage vs temperature temperature ( c) ?0 output voltage (v) 5.0 4.9 4.8 4.7 4.6 4.5 4.4 4.3 4.2 4.1 4.0 0 50 75 ltc1334 ?tpc01 ?5 25 100 125 i out = 3ma v cc = 5v temperature ( c) ?0 time (ns) 20 18 16 14 12 10 8 6 4 2 0 0 50 75 ltc1334 ?tpc03 ?5 25 100 125 v cc = 5v rs485 receiver skew ? t plh C t phl ? vs temperature temperature ( c) ?0 output voltage (v) 0.5 0.4 0.3 0.2 0.1 0 0 50 75 ltc1334 ?tpc02 ?5 25 100 125 i out = 3ma v cc = 5v receiver output low voltage vs temperature the l denotes specifications which apply over the full operating temperature range, otherwise specifications are at t a = 25 c. v cc = 5v, c1 = c2 = c3 = c4 = 0.1 m f (notes 2, 3) symbol parameter conditions min typ max units rs485 mode (sel1 = sel2 = high) t zl driver enable to output low figures 3, 7, c l = 100pf, s1 closed l 50 90 ns t zh driver enable to output high figures 3, 7, c l = 100pf, s2 closed l 50 90 ns t lz driver disable from low figures 3, 7, c l = 15pf, s1 closed l 50 90 ns t hz driver disable from high figures 3, 7, c l = 15pf, s2 closed l 60 90 ns t plh receiver input to output figures 2, 8, r l = 54 w , c l = 100pf l 20 60 140 ns t phl receiver input to output figures 2, 8, r l = 54 w , c l = 100pf l 20 70 140 ns t skew differential receiver skew, ? t plh C t phl ? figures 2, 8, r l = 54 w , c l = 100pf 10 ns
5 ltc1334 typical perfor m a n ce characteristics u w receiver output current vs output high voltage rs232 receiver input threshold voltage vs temperature receiver output current vs output low voltage output voltage (v) 2.0 output current (ma) 2.5 3.0 3.5 4.0 ltc1334 ?tpc04 4.5 20 18 16 14 12 10 8 6 4 2 0 5.0 t a = 25 c v cc = 5v output voltage (v) 0 0.5 output current (ma) 1.0 2.0 1.5 2.5 3.0 ltc1334 ?tpc05 40 35 30 25 20 15 10 5 0 t a = 25 c v cc = 5v temperature ( c) ?0 input threshold voltage (v) 2.0 1.8 1.6 1.4 1.2 1.0 0.8 25 75 ltc1334 ?tpc06 ?5 0 50 100 125 input high input low v cc = 5v charge pump output voltage vs temperature supply current vs temperature (rs232) supply current vs temperature (rs485) temperature ( c) ?0 output voltage (v) 10 8 6 4 2 0 ? ? ? ? ?0 0 50 75 ltc1334 ?tpc07 ?5 25 100 125 v dd (no load) v dd (?0ma load) v ee (10ma load) v ee (no load) v cc = 5v temperature ( c) ?0 0 supply current (ma) 10 25 0 50 75 ltc1334 ?tpc08 5 20 15 ?5 25 100 125 v cc = 5v no load sel 1 = sel 2 = high temperature ( c) ?0 supply current (ma) 10 9 8 7 6 5 4 3 2 1 0 0 50 75 ltc1334 ?tpc09 ?5 25 100 125 v cc = 5v no load sel 1 = sel 2 = high rs485 driver differential output voltage vs temperature rs485 driver skew vs temperature rs485 driver differential output current vs output voltage temperature ( c) ?0 differential output voltage (v) 2.6 2.5 2.4 2.3 2.2 2.1 2.0 1.9 1.8 1.7 1.6 0 50 75 ltc1334 ?tpc10 ?5 25 100 125 r l = 54 w v cc = 5v differential output voltage (v) 0 70 60 50 40 30 20 10 0 34 ltc1334 ?tpc11 12 5 differential output current (ma) t a = 25 c v cc = 5v temperature ( c) ?0 time ( m s) 15 12 9 6 3 0 0 50 75 ltc1334 ?tpc12 ?5 25 100 125 v cc = 5v
6 ltc1334 typical perfor m a n ce characteristics u w rs485 driver output high voltage vs output current rs485 driver output short-circuit current vs temperature rs485 driver output low voltage vs output current rs232 driver output voltage vs temperature driver output leakage current (disable/shutdown) vs temperature rs232 driver short-circuit current vs temperature output voltage (v) 0 output current (ma) 3 5 ltc1334 ?tpc13 12 4 ?0 ?0 ?0 ?0 ?0 ?0 ?0 ?0 0 t a = 25 c v cc = 5v output voltage (v) 0 output current (ma) 120 100 80 60 40 20 0 1234 ltc1334 ?tpc14 5 t a = 25 c v cc = 5v temperature ( c) ?0 output short-circuit current (ma) 160 140 120 100 80 60 40 25 75 ltc1334 ?tpc15 ?5 0 50 100 125 source (v out = 0v) sink (v out = 5v) v cc = 5v temperature ( c) ?0 output voltage (v) 10 8 6 4 2 0 ? ? ? ? ?0 0 50 75 ltc1334 ?tpc16 ?5 25 100 125 v cc = 5v r l = 3k output high output low temperature ( c) ?0 output short-circuit current (ma) 30 25 20 15 10 5 0 25 75 ltc1334 ?tpc17 ?5 0 50 100 125 source sink v out = 0v v cc = 5v temperature ( c) ?0 output leakage current ( a) 500 450 400 350 300 250 200 150 100 50 0 0 50 75 ltc1334 ?tpc18 ?5 25 100 125 v cc = 5v pi n fu n ctio n s uuu c1 + (pin 1): commutating capacitor c1 positive terminal. requires 0.1 m f external capacitor between pins 1 and 2. c1 C (pin 2): commutating capacitor c1 negative terminal. v dd (pin 3): positive supply output for rs232 drivers. requires an external 0.1 m f capacitor to ground. a1 (pin 4): receiver input. b1 (pin 5): receiver input. y1 (pin 6): driver output. z1 (pin 7): driver output. sel1 (pin 8): interface mode select input. sel2 (pin 9): interface mode select input. z2 (pin 10) : driver output. y2 (pin 11): driver output. b2 (pin 12): receiver input. a2 (pin 13): receiver input. gnd (pin 14): ground. v ee (pin 15): negative supply output. requires an exter- nal 0.1 m f capacitor to ground.
7 ltc1334 pi fu ctio s u uu r b2 (pin 16): receiver output. r a2 (pin 17): receiver output. d z2 /de2 (pin 18): rs232 driver input in rs232 mode. rs485 driver enable with internal pull-up in rs485 mode. d y2 (pin 19): driver input. on/off (pin 20): a high logic input enables the transceiv- ers. a low puts the device into shutdown mode and reduces i cc to 10 m a. this pin has an internal pull-up. lb (pin 21): loopback control input. a low logic level enables internal loopback connections. this pin has an internal pull-up. d y1 (pin 22): driver input. d z1 /de1 (pin 23): rs232 driver input in rs232 mode. rs485 driver enable with internal pull-up in rs485 mode. r a1 (pin 24): receiver output. r b1 (pin 25): receiver output. v cc (pin 26): positive supply; 4.75v v cc 5.25v c2 C (pin 27): commutating capacitor c2 negative termi- nal. requires 0.1 m f external capacitor between pins 27 and 28. c2 + (pin 28): commutating capacitor c2 positive terminal. fu ctio tables uu rs485 driver mode inputs outputs on/off sel de d conditions z y 1 1 1 0 no fault 0 1 1 1 1 1 no fault 1 0 1 1 1 x thermal fault z z 110x x zz 01xx x zz rs232 driver mode inputs outputs on/off sel d conditions y, z 1 0 0 no fault 1 1 0 1 no fault 0 1 0 x thermal fault z 00x x z rs485 receiver mode inputs outputs on/off sel b C a r a r b * 1 1 < C 0.2v 0 1 1 1 > 0.2v 1 1 1 1 inputs open 1 1 01 xzz *see note 5 of electrical characteristics table. rs232 receiver mode inputs outputs on/off sel a, b r a , r b 10 0 1 10 1 0 1 0 inputs open 1 00 x z 1 28 c2 + c2 c1 + v ee r b2 r a2 d z2 /de2 d y2 on/off lb d y1 d z1 /de1 r a1 r b1 v cc 14 15 13 12 11 10 9 8 7 6 5 4 3 2 16 17 18 19 20 21 22 23 24 25 26 27 gnd a2 b2 y2 z2 sel2 sel1 z1 y1 b1 a1 v dd c1
8 ltc1334 block diagra s m w interface configuration with loopback disabled interface configuration with loopback enabled port 1 = rs232 mode port 2 = rs232 mode lb 20 21 14 r b1 c2 c1 r a1 d z1 d y1 b1 a1 v dd v cc sel1 = 0v 27 28 1 4 2 3 6 7 8 26 24 23 22 on v ee 15 y1 z1 5 25 d y2 d z2 r a2 r b2 d y2 d z2 r a2 r b2 y2 z2 sel2 = 0v 12 13 10 9 18 17 16 b2 a2 gnd 11 19 ltc1334 ?bd01 v dd v dd v dd port 1 = rs485 mode port 2 = rs232 mode lb 20 21 14 r b1 c2 c1 r a1 de1 d y1 b1 a1 v cc sel1 = 5v 27 28 1 4 2 3 6 7 8 26 24 23 22 on v ee 15 y1 z1 5 25 y2 z2 sel2 = 0v 12 13 10 9 18 17 16 b2 a2 gnd 11 19 port 1 = rs232 mode port 2 = rs485 mode lb 20 21 14 r b1 c2 c1 r a1 d z1 d y1 b1 a1 v cc sel1 = 0v 27 28 1 4 2 3 6 7 8 26 24 23 22 on v ee 15 y1 z1 5 25 d y2 de2 r a2 r b2 y2 z2 sel2 = 5v 12 13 10 9 18 17 16 b2 a2 gnd 11 19 port 1 = rs485 mode port 2 = rs485 mode lb 20 21 14 r b1 c2 c1 r a1 de1 d y1 b1 a1 v cc sel1 = 5v 27 28 1 4 2 3 6 7 8 26 24 23 22 on v ee 15 y1 z1 5 25 d y2 de2 r a2 r b2 y2 z2 sel2 = 5v 12 13 10 9 18 17 16 b2 a2 gnd 11 19 port 1 = rs232 mode port 2 = rs232 mode 20 21 14 r b1 c2 c1 r a1 d z1 d y1 v dd v cc sel1 = 0v 27 28 1 2 3 6 7 8 26 24 23 22 on v ee 15 y1 z1 25 d y2 d z2 r a2 r b2 d y2 d z2 r a2 r b2 y2 z2 sel2 = 0v 10 9 18 17 16 gnd 11 19 ltc1334 ?bd02 v dd v dd v dd port 1 = rs485 mode port 2 = rs232 mode 20 21 14 r b1 c2 c1 r a1 de1 d y1 v cc sel1 = 5v 27 28 1 2 3 6 7 8 26 24 23 22 on v ee 15 y1 z1 25 y2 z2 sel2 = 0v 10 9 18 17 16 gnd 11 19 port 1 = rs232 mode port 2 = rs485 mode 20 21 14 r b1 c2 c1 r a1 d z1 d y1 v cc sel1 = 0v 27 28 1 2 3 6 7 8 26 24 23 22 on v ee 15 y1 z1 25 d y2 de2 r a2 r b2 y2 z2 sel2 = 5v 10 9 18 17 16 gnd 11 19 port 1 = rs485 mode port 2 = rs485 mode 20 21 14 r b1 c2 c1 r a1 de1 d y1 v cc sel1 = 5v 27 28 1 2 3 6 7 8 26 24 23 22 on v ee 15 y1 z1 25 d y2 de2 r a2 r b2 y2 z2 sel2 = 5v 10 9 18 17 16 gnd 11 19 lb lb lb lb
9 ltc1334 test circuits figure 2. rs485 driver/receiver timing test circuit figure 1. rs422/rs485 driver test load r r v od y z ltc1334 ?f01 v oc r l c l ltc1334 ?f02 y 3v 3v sel de z c l a sel 3v r b 15pf d dr out c l 500 w s2 ltc1334 ?f03 v cc s1 figure 4. rs232 driver swing/timing test circuit r l ltc1334 ?f04 y, z 0v sel d c l figure 5. rs232 receiver timing test circuit switchi g wavefor s u w figure 3. rs485 driver output enable/disable timing test load 1.5v 3v 0v d f = 1mhz: t r 10ns: t f 10ns 1.5v z y ? o v o t skew 1/2 v o ltc1334 ?f06 t plh t r 90% 50% 10% t phl t f 90% 50% 10% v o t skew v diff = v(z) ?v(y) z y figure 6. rs485 driver propagation delays ltc1334 ?f05 15pf y, z 0v sel d r 0v sel a, b v in v out
10 ltc1334 switchi g wavefor s u w 1.5v 3v 0v de f = 1mhz: t r 10ns: t f 10ns 1.5v y, z v ol 5v t zl t lz 0.5v output normally low 0v ltc1334 ?f07 2.3v 2.3v t zh v oh output normally high t hz 0.5v z, y 0v v od2 b ?a f = 1mhz: t r 10ns: t f 10ns 1.5v r v ol v oh ltc1334 ?f08 t plh t phl input ? od2 output 0v 1.5v 3v d y, z ? o v o ltc1334 ?f09 t phl t plh 0v 0v 0v 1.5v 1.5v v ih a, b r v ol v oh ltc1334 f10 t phl t plh v il 2.4v 0.8v 1.3v 1.7v figure 7. rs485 driver enable and disable times figure 8. rs485 receiver propagation delays figure 10. rs232 receiver propagation delays figure 9. rs232 driver propagation delays
11 ltc1334 u s a o pp l ic at i wu u i for atio basic theory of operation the ltc1334 has two interface ports. each port may be configured as a pair of single-ended rs232 transceivers or as a differential rs485 transceiver by forcing the ports selection input to a low or high, respectively. the ltc1334 provides two rs232 drivers and two rs232 receivers or one rs485 driver and one rs485 receiver per port. all the interface drivers feature three-state outputs. interface outputs are forced into high imped- ance when the driver is disabled, in the shutdown mode or with the power off. all the interface driver outputs are fault-protected by a current limiting and thermal shutdown circuit. the ther- mal shutdown circuit disables both the rs232 and rs485 driver outputs when the die temperature reaches 150 c. the thermal shutdown circuit reenables the drivers when the die temperature cools to 130 c. in rs485 mode, shutdown mode or with the power off, the input resistance of the receiver is 24k. the input resistance drops to 5k in rs232 mode. a logic low at the on/off pin shuts down the device and forces all the outputs into a high impedance state. a logic high enables the device. an internal 4 m a current source to v cc pulls the on/off pin high if it is left open. figure 11. rs232/rs485 interfaces 1 28 v cc 5v ltc1334 ?f11 120 w 12 21 ltc1334 rx out 18 5v 13 10 11 9 8 14 17 16 rs485 i/o rs232 dr out 19 5v 20 15 v ee 5v 3 5v into 3k w load 5 4 27 26 24 rx out 6 rs232 rx in 23 2 3 rx out 7 dr in dr enable dr in dr in 22 rs232 dr out rs232 rx in v dd c1 c2 0.1 f 0.1 f 0.1 f 0.1 f 0.1 f in rs485 mode, an internal 4 m a current source pulls the driver enable pin high if left open. the rs485 receiver has a 4 m a current source at the noninverting input. if both the rs485 receiver inputs are open, the output goes to a high state. both the current sources are disabled in the rs232 mode. the receiver output b is inactive in rs485 mode and has a 50k pull-up resistor to provide a known output state in this mode. a loopback mode enables internal connections from driver outputs to receiver inputs for self-test when the lb pin has a low logic state. the driver outputs are not isolated from the external loads. this allows transmitter verification under the loaded condition. an internal 4 m a current source pulls the lb pin high if left open and disables the loopback configuration. rs232/rs485 applications the ltc1334 can support both rs232 and rs485 levels with a single 5v supply as shown in figure 11. multiprotocol applications the ltc1334 is well-suited for software controlled inter- face mode selection. each port has a selection pin as shown in figure 12. the single-ended transceivers sup- port both rs232 and eia562 levels. the differential trans- ceivers support both rs485 and rs422.
12 ltc1334 u s a o pp l ic at i wu u i for atio figure 12. multiprotocol interface with optional, switchable terminations 326 25 rx out 24 rx out 22 dr in 8 sel1 23 21 dr in/enable lb v cc 5v ltc1334 ?f12 ltc1334 28 c2 c1 2 1 27 v ee v dd 4 input a k1a k1b 120 5 input b 6 output a 7 output b 13 input a 12 input b 11 output a 10 14 output b port 1 interface 20 16 on/off rx out 17 rx out 19 dr in 9 sel2 18 15 dr in/enable port 2 interface aromat corp (800) 276-6289 zetex (516) 543-7100 * ** 0.1 f 0.1 f 0.1 f 0.1 f 0.1 f 120 k2a 120 k2b 120 term1 360k fmmt619** k1* tx2a-5v 7.5k term2 360k fmmt619** k2* tx2a-5v 7.5k 5v 5v figure 13. typical connection for rs232/eia562 interface 1/2 ltc1334 1/2 ltc1334 ltc1334 ?f13 19 18 17 16 9 dr in dr in rx out rx out 4 5 6 7 11 10 13 12 24 25 22 23 8 rx out rx out dr in dr in rs232/ eia562 interface lines each receiver in the ltc1334 is designed to present one unit load (5k w nominal for rs232 and 12k w minimum for rs485) to the cable. some rs485 and rs422 applications call for terminations, but these are only necessary at two nodes in the system and they must be disconnected when operating in the rs232 mode. a relay is the simplest, low- est cost method of switching terminations. in figure 12 term1 and term2 select 120 w terminations as needed. if terminations are needed in all rs485/rs422 applica- tions, no extra control signals are required; simply con- nect term1 and term2 to sel1 and sel2. typical applications a typical rs232/eia562 interface application is shown in figure 13 with the ltc1334. a typical connection for a rs485 transceiver is shown in figure 14. a twisted pair of wires connects up to 32 drivers and receivers for half duplex multipoint data transmission. the wires must be terminated at both ends with resistors equal to the wires characteristic impedance. an optional shield around the twisted pair helps to reduce unwanted noise and should be connected to ground at only one end. figure 14. typical connection for rs485 interface 5v 4 1/2 ltc1334 1/2 ltc1334 1/2 ltc1334 ltc1334 f14 rx out dr enable dr in 5v 120 w 5 6 7 24 23 22 8 13 12 11 10 9 rx out 18 5v dr enable 76 54 22 dr in rx out dr enable 23 24 8 17 dr in 19 120 w
13 ltc1334 figure 18. typical cable extension for rs232/eia562 interface u s a o pp l ic at i wu u i for atio rs422 rs232/eia562 ltc1334 ?f18 100 w 100 w 13 11 9 19 24 23 22 17 8 dr out rx in 5v 4 5 6 7 ltc1334 rs232/eia562 22 11 13 17 5v 9 19 24 23 8 4 5 6 7 rx in dr out ltc1334 rs422 rs232/eia562 ltc1334 ?f17 100 w 13 11 9 19 24 23 22 17 8 tx out tx out rx in rx in 5v 4 5 6 7 ltc1334 figure 17. typical rs232/eia562 to rs422 level translator figure 16. typical cable repeater for rs422 interface 1/2 ltc1334 tx out rx in ltc1334 ?f16 100 w 4 5 6 8 23 22 24 7 5v 1/2 ltc1334 1/2 ltc1334 1/2 ltc1334 ltc1334 ?f15 100 w 22 23 8 24 8 17 18 19 5v 5v rx out rx out rx out dr enable dr enable dr in dr in 5 4 8 5v 4 5 6 7 11 10 13 24 12 100 w figure 15. typical connection for rs422 interface a typical rs422 connection (figure 15) allows one driver and ten receivers on a twisted pair of wires terminated with a 100 w resistor at one end. a typical twisted-pair line repeater is shown in figure 16. as data transmission rate drops with increased cable length, repeaters can be inserted to improve transmission rate or to transmit beyond the rs422 4000-foot limit. the ltc1334 can be used to translate rs232 to rs422 interface levels or vice versa as shown in figure 17. one port is configured as an rs232 transceiver and the other as an rs485 transceiver. using two ltc1334s as level translators, the rs232/ eia562 interface distance can be extended to 4000 feet with twisted-pair wires (figure 18). appletalk ? /localtalk ? applications two appletalk applications are shown in figure 19 and 20 with the ltc1323 and the ltc1334. appletalk and localtalk are registered trademarks of apple computer, inc.
14 ltc1334 5v 0.33 m f 0.33 m f 1 m f 3 26 5v 1 txd rxd txd + rxd + 120 w 2 ltc1323cs-16 ltc1334 ?f19 txd 7 3 4 1k 1k rxen 5 6 21 ltc1334 18 r a1 4 5 10 9 8 13 14 17 de1 d y1 19 5v 5v 20 16 15 120 w sel1, 5v sel2, 5v 11 24 6 23 8 16 15 10 14 13 12 11 9 12 25 7 22 28 2 1 27 txden shdn rxdo 1k 1k charge pump 0.1 m f 0.1 m f 0.1 m f 0.1 m f emi emi emi emi emi emi emi emi 100pf 100pf 5 w to 22 w 5 w to 22 w 100pf ferrite bead ferrite bead = or or emi nc nc nc nc nc nc nc nc nc u s a o pp l ic at i wu u i for atio figure 20. appletalk direct connect using the ltc1323 dte and the ltc1334 for dce transceivers 5v 0.33 m f 0.33 m f 1 m f 3 26 5v 1 txd txo txd + rxi 120 w 2 ltc1323cs ltc1334 ?f20 cpen 7 3 4 txden 5 6 21 ltc1334 18 r a1 r a2 4 5 10 9 8 13 14 17 de1 d y1 d y2 d z2 19 5v 5v 20 16 15 120 w 120 w 120 w sel1 5v sel2 11 24 6 23 12 24 23 18 22 21 20 19 17 rxi 16 rxd 15 rxd + 14 13 12 25 7 22 28 2 1 27 txd txi shdn 8 rxen 9 rxo 10 11 rxo rxdo charge pump 0.1 m f 0.1 m f 0.1 m f 0.1 m f emi emi emi emi emi emi emi emi emi emi emi emi nc nc nc 100pf 100pf 5 w to 22 w 5 w to 22 w 100pf ferrite bead ferrite bead = or or emi emi emi figure 19. appletalk/localtalk implemented using the ltc1323cs-16 and ltc1334 transceivers
15 ltc1334 dimensions in inches (millimeters) unless otherwise noted. package descriptio n u nw package 28-lead pdip (wide 0.600) (ltc dwg # 05-08-1520) g package 28-lead plastic ssop (0.209) (ltc dwg # 05-08-1640) g28 ssop 1098 0.13 ?0.22 (0.005 ?0.009) 0 ?8 0.55 ?0.95 (0.022 ?0.037) 5.20 ?5.38** (0.205 ?0.212) 7.65 ?7.90 (0.301 ?0.311) 1234 5 6 7 8 9 10 11 12 14 13 10.07 ?10.33* (0.397 ?0.407) 25 26 22 21 20 19 18 17 16 15 23 24 27 28 1.73 ?1.99 (0.068 ?0.078) 0.05 ?0.21 (0.002 ?0.008) 0.65 (0.0256) bsc 0.25 ?0.38 (0.010 ?0.015) note: dimensions are in millimeters dimensions do not include mold flash. mold flash shall not exceed 0.152mm (0.006") per side dimensions do not include interlead flash. interlead flash shall not exceed 0.254mm (0.010") per side * ** 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 represen- tation that the interconnection of its circuits as described herein will not infringe on existing patent rights. n28 1098 0.505 ?0.560* (12.827 ?14.224) 1.455* (36.957) max 12 3 4 5 6 7 8 9 10 27 19 20 21 22 24 23 25 26 28 11 12 13 14 15 16 17 18 0.009 ?0.015 (0.229 ?0.381) 0.625 +0.035 0.015 +0.889 0.381 15.87 () 0.600 ?0.625 (15.240 ?15.875) 0.070 (1.778) typ 0.015 (0.381) min 0.125 (3.175) min 0.150 0.005 (3.810 0.127) 0.018 0.003 (0.457 0.076) 0.035 ?0.080 (0.889 ?2.032) 0.100 (2.54) bsc 0.045 ?0.065 (1.143 ?1.651) *these dimensions do not include mold flash or protrusions. mold flash or protrusions shall not exceed 0.010 inch (0.254mm)
16 ltc1334 1334fa lt/tp 1099 2k rev a ? printed in usa ? linear technology corporation 1995 dimensions in inches (millimeters) unless otherwise noted. package descriptio n u sw package 28-lead plastic small outline (wide 0.300) (ltc dwg # 05-08-1690) related parts part number description comments ltc485 low power rs485 interface transceiver single 5v supply, wide common mode range lt ? 1137a low power rs232 transceiver 15kv iec-1000-4-2 esd protection, three drivers, five receivers ltc1320 appletalk transceiver appletalk/local talk compliant ltc1321/ltc1322/ltc1335 rs232/eia562/rs485 transceivers configurable, 10kv esd protection ltc1323 single 5v appletalk transceiver localtalk/appletalk compliant 10kv esd ltc1347 5v low power rs232 transceiver three drivers/five receivers, five receivers alive in shutdown ltc1387 single 5v rs232/rs485 transceiver single port, configurable, 10kv esd linear technology corporation 1630 mccarthy blvd., milpitas, ca 95035-7417 (408) 432-1900 l fax: (408) 434-0507 l www.linear-tech.com s28 (wide) 1098 0 ?8 typ note 1 0.009 ?0.013 (0.229 ?0.330) 0.016 ?0.050 (0.406 ?1.270) 0.291 ?0.299** (7.391 ?7.595) 45 0.010 ?0.029 (0.254 ?0.737) 0.037 ?0.045 (0.940 ?1.143) 0.004 ?0.012 (0.102 ?0.305) 0.093 ?0.104 (2.362 ?2.642) 0.050 (1.270) bsc 0.014 ?0.019 (0.356 ?0.482) typ note 1 0.697 ?0.712* (17.70 ?18.08) 1 23 4 5 6 78 0.394 ?0.419 (10.007 ?10.643) 910 25 26 11 12 22 21 20 19 18 17 16 15 23 24 14 13 27 28 note: 1. pin 1 ident, notch on top and cavities on the bottom of packages are the manufacturing options. the part may be supplied with or without any of the options dimension does not include mold flash. mold flash shall not exceed 0.006" (0.152mm) per side dimension does not include interlead flash. interlead flash shall not exceed 0.010" (0.254mm) per side * **

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