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1 lt1780/lt1781 low power 5v rs232 dual driver/receiver with 15kv esd protection transzorb is a registered trademark of general instruments, gsi. r output waveforms 1780/81 ? ta02 driver output r l = 3k c l = 2500pf receiver output c l = 50pf input 0.1 m f 0.1 m f 0.1 m f 0.1 m f logic inputs logic outputs on/off 18 10 13 11 12 6 5 4 2 16 9 14 8 15 7 3 17 5v input v + out v out rs232 output rs232 output rs232 input rs232 input 1780/81 ta01 5k 5k lt1780 u a o pp l ic at i ty p i ca l s f ea t u re d u escriptio the lt ? 1780/lt1781 are dual rs232 driver/receiver pairs with integral charge pump to generate rs232 voltage levels from a single 5v supply. using only 0.1 m f external capacitors, these circuits consume only 40mw of power, and can operate to 120kbaud even while driving heavy capacitive loads. new esd structures on the chip allow the lt1780/lt1781 to survive 15kv air gap and 8kv con- tact esd tests per iec 1000-4-2, eliminating the need for costly transzorbs ? on the rs232 line pins. the lt1780/ lt1781 are fully compliant with eia rs232 standards. driver outputs are protected from overload, and can be shorted to ground or up to 30v without damage. during shutdown or power-off conditions, driver and receiver outputs are in a high impedance state, allowing line sharing. the lt1780/lt1781 are direct upgrades to the lt1180a/ lt1181a, lt1280a/lt1281a and lt1381 for applications which require the utmost esd protection. the lt1781 is available in 16-pin dip,so and sw pack- ages. the lt1780 is supplied in 18-pin dip and sw packages for applications which require shutdown. n 10ma max supply current n esd protection to iec 1000-4-2 level 4 15kv air gap, 8kv contact n uses small capacitors: 0.1 m f n 120kbaud operation for r l = 3k, c l = 2500pf n 250kbaud operation for r l = 3k, c l = 1000pf n outputs withstand 30v without damage n cmos comparable low power: 40mw n operates from a single 5v supply n rugged bipolar design n outputs assume a high impedance state when off or powered down n meets all rs232 specifications n available with or without shutdown n absolutely no latch-up n portable computers n battery-powered systems n power supply generator n terminals n modems u s a o pp l ic at i , ltc and lt are registered trademarks of linear technology corporation.
2 lt1780/lt1781 a u g w a w u w a r b s o lu t exi t i s supply voltage (v cc ) ................................................ 6v v + ........................................................................ 13.2v v C ...................................................................... C13.2v input voltage driver ........................................................... v C to v + receiver ............................................... C 30v to 30v on/off ................................................. C 0.3v to 12v output voltage driver ...................................... v + C 30v to v C + 30v receiver .................................... C 0.3v to v cc + 0.3v short-circuit duration v + ................................................................... 30 sec v C ................................................................... 30 sec driver output .............................................. indefinite receiver output .......................................... indefinite operating temperature range ..................... 0 c to 70 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 order part number order part number lt1780cn lt1780csw lt1781cn lt1781cs lt1781csw (note 2) e lectr ic al c c hara terist ics parameter conditions min typ max units power supply generator v + output 7.9 v v C output C7 v supply current (v cc ) (note 3), t a = 25 c 8 10 ma l 14 ma supply current when off (v cc ) shutdown (note 4) lt1780 only l 110 m a supply rise time c1 = c2 = c3 = c4 = 0.1 m f 0.2 ms shutdown to turn-on lt1780 only 0.2 ms on/off pin thresholds input low level (device shutdown) l 0.8 1.2 v input high level (device enabled) l 1.6 2.4 v on/off pin current 0v v on/off 5v l C15 80 m a oscillator frequency 130 khz driver output voltage swing load = 3k to gnd positive l 5.0 7.5 v negative l C 6.3 C 5 v logic input voltage level input low level (v out = high) l 1.4 0.8 v input high level (v out = low) l 2.0 1.4 v 1 2 3 4 5 6 7 8 9 top view 18 17 16 15 14 13 12 11 10 nc c1 + v + c1 c2 + c2 v tr2 out rec2 in n package 18-lead plastic dip on/off v cc gnd tr1 out rec1 in rec1 out tr1 in tr2 in rec2 out sw package 18-lead plastic so t jmax = 125 c, q ja = 80 c/ w, q jc = 36 c/w (n) t jmax = 125 c, q ja = 90 c/ w, q jc = 26 c/w (sw) 1 2 3 4 5 6 7 8 top view 16 15 14 13 12 11 10 9 c1 + v + c1 c2 + c2 v tr2 out rec2 in v cc gnd tr1 out rec1 in rec1 out tr1 in tr2 in rec2 out n package 16-lead plastic dip s package 16-lead plastic so sw package 16-lead plastic so t jmax = 125 c, q ja = 90 c/ w, q jc = 46 c/w (n) t jmax = 125 c, q ja = 95 c/ w, q jc = 34 c/w (s) t jmax = 125 c, q ja = 95 c/ w, q jc = 27 c/w (sw) consult factory for industrial and military grade parts. (note 1)
3 lt1780/lt1781 e lectr ic al c c hara terist ics (note 2) parameter conditions min typ max units logic input current 0.8v v in 2.0v l 520 m a output short-circuit current v out = 0v 717 ma output leakage current shutdown v out = 30v (note 4) l 10 100 m a data rate r l = 3k, c l = 2500pf 120 kbaud r l = 3k, c l = 1000pf 250 kbaud slew rate r l = 3k, c l = 51pf 15 30 v/ m s r l = 3k, c l = 2500pf 4 7 v/ m s propagation delay output transition t hl high-to-low (note 5) 0.6 1.3 m s output transition t lh low-to-high 0.5 1.3 m s receiver input voltage thresholds input low threshold (v out = high) 0.8 1.3 v input high threshold (v out = low) 1.7 2.4 v hysteresis l 0.1 0.4 1 v input resistance v in = 10v 357 k w output leakage current shutdown (note 4) 0 v out v cc l 110 m a output voltage output low, i out = C 1.6ma l 0.2 0.4 v output high, i out = 160 m a (v cc = 5v) l 3.5 4.2 v output short-circuit current sinking current, v out = v cc C10 ma sourcing current, v out = 0v 10 20 ma propagation delay output transition t hl high-to-low (note 6) 250 600 ns output transition t lh low-to-high 350 600 ns note 4: supply current measurements in shutdown are performed with v on/off 0.1v. note 5: for driver delay measurements, r l = 3k and c l = 51pf. trigger points are set between the drivers input logic threshold and the output transition to the zero crossing (t hl = 1.4v to 0v and t lh = 1.4v to 0v). note 6: for receiver delay measurements, c l = 51pf. trigger points are set between the receivers input logic threshold and the output transition to standard ttl/cmos logic threshold (t hl = 1.3v to 2.4v and t lh = 1.7v to 0.8v). the l denotes specifications which apply over the operating temperature range. note 1: absolute maximum ratings are those values beyond which the life of the device may be impaired. note 2: testing done at v cc = 5v and v on/off = 3v, unless otherwise specified. note 3: supply current is measured as the average over several charge pump cycles. c + = c C = c1 = c2 = 0.1 m f. all outputs are open, with all driver inputs tied high. C20
4 lt1780/lt1781 cc hara terist ics uw a t y p i ca lper f o r c e receiver input thresholds on/off thresholds temperature ( c) ?5 0.50 threshold voltage (v) 0.75 1.25 1.50 1.75 3.00 2.25 0 50 75 1780 ?g04 1.00 2.50 2.75 2.00 ?5 25 100 125 input high input low data rate (kbaud) 0 0 supply current (ma) 10 20 30 40 50 25 50 75 100 1780 ?g05 125 150 2 drivers active r l = 3k c l = 2500pf supply current vs data rate temperature ( c) ?5 threshold voltage (v) 2.0 2.5 3.0 25 75 1780 ?g06 1.5 1.0 ?5 0 50 100 125 0.5 0 on threshold off threshold supply current temperature ( c) ?5 0 supply current (ma) 10 25 0 50 75 1780 ?g07 5 20 15 ?5 25 100 125 2 drivers loaded r l = 3k 1 driver loaded r l = 3k no load driver output voltage driver minimum output voltage vs load capacitance driver maximum output voltage vs load capacitance load capacitance (nf) 0 5.0 peak output voltage (v) 5.5 6.0 6.5 7.0 7.5 8.0 2468 1780 ?g01 10 13579 20k baud 60k baud 120k baud load capacitance (nf) 0 7.0 peak output voltage (v) 6.5 6.0 5.5 5.0 4.5 4.0 2468 1780 ?g02 10 13579 120k baud 60k baud 20k baud temperature ( c) ?5 ?0 driver output voltage (v) ? ? ? 0 10 4 0 50 75 1780 ?g03 ? 6 8 2 ?5 25 100 125 output high output low r l = 3k v cc = 5v v cc = 4.5v v cc = 5.5v v cc = 4.5v v cc = 5v v cc = 5.5v
5 lt1780/lt1781 cc hara terist ics uw a t y p i ca lper f o r c e shutdown to driver outputs driver output waveforms 1780 ? g13 1780 ? g12 input driver output r l = 3k driver output r l = 3k c l = 2500pf 10v 5v gnd driver 1 output driver 2 output on/off pin gnd C 10v C5v driver leakage in shutdown receiver short-circuit current slew rate vs load capacitance temperature ( c) 0.1 leakage current ( m a) 10 100 1780 ?g08 1 ?5 0 50 75 ?5 25 100 125 v out = 30v v out = 30v driver short-circuit current temperature ( c) ?5 short-circuit current (ma) 20 25 30 25 75 1780 ?g09 15 10 ?5 0 50 100 125 5 0 isc + isc temperature ( c) ?5 0 short-circuit current (ma) 20 50 0 50 75 1780 ?g10 10 40 30 ?5 25 100 125 rx isc rx isc + load capacitance (nf) 0 slew rate (v/ s) 12 16 4.0 1780 ?g11 8 4 0 1.0 2.0 3.0 5.0 10 14 6 2 3.5 0.5 1.5 2.5 4.5 +slew slew
6 lt1780/lt1781 v cc : 5v input supply pin. this pin should be decoupled with a 0.1 m f ceramic capacitor close to the package pin. insufficient supply bypassing can result in low output drive levels and erratic charge pump operation. gnd: ground pin. on/off: a ttl/cmos compatible operating mode con- trol. a logic low puts the lt1780 in shutdown mode. supply current drops to zero and both driver and receiver outputs assume a high impedance state. a logic high fully enables the device. v + : positive supply output (rs232 drivers). v + ? 2v cc C 1.5v. this pin requires an external charge storage capacitor c 3 0.1 m f, tied to ground or v cc . larger value capacitors may be used to reduce supply ripple. with multiple transceivers, the v + and v C pins may be paralleled into common capacitors. v C : negative supply output (rs232 drivers). v C ? C(2v cc C 2.5v). this pin requires an external charge storage capacitor c 3 0.1 m f. larger value capacitors may be used to reduce supply ripple. with multiple transceiv- ers, the v + and v C pins may be paralleled into common capacitors. tr1 in, tr2 in: rs232 driver input pins. these inputs are ttl/cmos compatible. inputs should not be allowed to float. tie unused inputs to v cc . tr1 out, tr2 out: driver outputs at rs232 voltage levels. driver output swing meets rs232 levels for loads up to 3k. slew rates are controlled for lightly loaded lines. output current capability is sufficient for load conditions up to 2500pf. outputs are in a high impedance state when in shutdown mode or v cc = 0v. outputs are fully short- circuit protected from v C + 30v to v + C 30v. applying higher voltages will not damage the device if the overdrive is moderately current limited. short circuits on one output can load the power supply generator and may disrupt the signal levels of the other outputs. the driver outputs are protected against esd to iec-1000-4-2 level 4 discharges. rec1 in, rec2 in: receiver inputs. these pins accept rs232 level signals ( 30v) into a protected 5k terminat- ing resistor. the receiver inputs are protected against esd to iec-1000-4-2 level 4 discharges. each receiver pro- vides 0.4v of hysteresis for noise immunity. open receiver inputs result in a logic high receiver output state. rec1 out, rec2 out: receiver outputs with ttl/cmos voltage levels. outputs are in a high impedance state when in shutdown mode to allow data line sharing. outputs are fully short-circuit protected to ground or v cc with the power on, off or in the shutdown mode. c1 + , c1 C , c2 + , c2 C : commutating capacitor inputs. these pins require two external capacitors c 3 0.1 m f: one from c1 + to c1 C and another from c2 + to c2 C . c1 should be deleted if a separate 12v supply is available and connected to pin c1 + . similarly, c2 should be deleted if a separate C 12v supply is connected to pin v C . pi fu ctio s u uu
7 lt1780/lt1781 esd protectio u the rs232 line inputs of the lt1780/lt1781 have on-chip protection from esd transients up to 15kv air gap and 8kv contact tested to iec-1000-4-2 test methods. the protection structures act to divert the static discharge safely to system ground. in order for the esd protection to function effectively, the power supply and ground pins of the circuit must be connected to ground through low impedances. the power supply decoupling capacitors and charge pump storage capacitors provide this low imped- ance in normal application of the circuit. the only con- straint is that low esr capacitors must be used for bypassing and charge storage. esd testing must be done with pins v cc , v l , v + , v C , and gnd shorted to ground or connected with low esr capacitors. operation using 5v and 12v power supplies 1780 ?esd tc 0.1 m f rs232 line pins protected to iec-1000-4-2 level 4 1 2 3 4 5 6 7 8 9 18 17 16 15 14 13 12 11 10 0.1 m f 0.1 m f 0.1 m f nc c1 + v + c1 c2 + c2 v dr2 out lt1780 0.1 m f on/off 5v v cc gnd dr1 out rx1 in rx1 out dr1 in dr2 in rs232 line pins protected to iec-1000-4-2 level 4 rx2 in rx2 out esd test circuit 5k 5k 0.1 m f 0.1 m f logic inputs logic outputs on/off 18 10 13 11 12 6 5 4 2 16 9 14 8 15 7 3 17 5v input 12v out rs232 output rs232 output rs232 input rs232 input 1780/81 ta03 lt1780 12v input u typical applicatio
8 lt1780/lt1781 n package 16-lead pdip (narrow 0.300) (ltc dwg # 05-08-1510) n package 18-lead pdip (narrow 0.300) (ltc dwg # 05-08-1510) package descriptio u dimensions in inches (millimeters) unless otherwise noted. n16 1197 0.255 0.015* (6.477 0.381) 0.770* (19.558) max 16 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 0.020 (0.508) min 0.125 (3.175) min 0.130 0.005 (3.302 0.127) 0.065 (1.651) typ 0.045 ?0.065 (1.143 ?1.651) 0.018 0.003 (0.457 0.076) 0.100 0.010 (2.540 0.254) 0.009 ?0.015 (0.229 ?0.381) 0.300 ?0.325 (7.620 ?8.255) 0.325 +0.035 0.015 +0.889 0.381 8.255 () *these dimensions do not include mold flash or protrusions. mold flash or protrusions shall not exceed 0.010 inch (0.254mm) n18 1197 0.020 (0.508) min 0.125 (3.175) min 0.130 0.005 (3.302 0.127) 0.065 (1.651) typ 0.045 ?0.065 (1.143 ?1.651) 0.018 0.003 (0.457 0.076) 0.005 (0.127) min 0.100 0.010 (2.540 0.254) 0.255 0.015* (6.477 0.381) 0.900* (22.860) max 18 12 3 4 56 7 8 9 10 11 12 13 14 16 15 17 0.009 ?0.015 (0.229 ?0.381) 0.300 ?0.325 (7.620 ?8.255) 0.325 +0.035 0.015 +0.889 0.381 8.255 () *these dimensions do not include mold flash or protrusions. mold flash or protrusions shall not exceed 0.010 inch (0.254mm)
9 lt1780/lt1781 package descriptio u dimensions in inches (millimeters) unless otherwise noted. sw package 16-lead plastic small outline (wide 0.300) (ltc dwg # 05-08-1620) s16 (wide) 0396 note 1 0.398 ?0.413* (10.109 ?10.490) 16 15 14 13 12 11 10 9 1 23 4 5 6 78 0.394 ?0.419 (10.007 ?10.643) 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) typ 0.014 ?0.019 (0.356 ?0.482) typ 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) 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 * **
10 lt1780/lt1781 package descriptio u dimensions in inches (millimeters) unless otherwise noted. sw package 18-lead plastic small outline (wide 0.300) (ltc dwg # 05-08-1620) s18 (wide) 0396 see note 0.447 ?0.463* (11.354 ?11.760) 15 14 13 12 11 10 16 9 1 23 4 5 6 78 0.394 ?0.419 (10.007 ?10.643) 17 18 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) typ 0.014 ?0.019 (0.356 ?0.482) typ 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) 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 * **
11 lt1780/lt1781 package descriptio u dimensions in inches (millimeters) unless otherwise noted. s package 16-lead plastic small outline (narrow 0.150) (ltc dwg # 05-08-1610) 0.016 ?0.050 0.406 ?1.270 0.010 ?0.020 (0.254 ?0.508) 45 0 ?8 typ 0.008 ?0.010 (0.203 ?0.254) 1 2 3 4 5 6 7 8 0.150 ?0.157** (3.810 ?3.988) 16 15 14 13 0.386 ?0.394* (9.804 ?10.008) 0.228 ?0.244 (5.791 ?6.197) 12 11 10 9 s16 0695 0.053 ?0.069 (1.346 ?1.752) 0.014 ?0.019 (0.355 ?0.483) 0.004 ?0.010 (0.101 ?0.254) 0.050 (1.270) typ 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 * ** 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.
12 lt1780/lt1781 17801f lt/tp 0498 4k ? printed in usa ? linear technology corporation 1998 u typical applicatio supporting an lt1039 (triple driver/receiver) 30k 30k rs232 output rs232 output rs232 input rs232 input 1780/81 ta04 lt1039 ttl input 30k rs232 input v cc ttl input ttl input ttl output ttl output ttl output on/off rs232 output 5k rs232 output rs232 input lt1780 ttl input 5k rs232 input v cc ttl input ttl output ttl output on/off rs232 output 1 m f 2 4 1 m f 5 6 3 7 18 17 1 m f 1 m f gnd 16 gnd 10 v + v 1 9 18 17 5v shutdown c2 c2 + c1 c1 + v + v 11 12 13 10 15 14 9 8 12 14 16 11 13 15 7 5 3 8 6 4 related parts part number description comments LT1137A 3driver/5receiver rs232 transceiver iec-1000-4-2 level 4 esd compliance ltc1383 5v low power rs232 2driver/2receiver transceiver low supply current i cc = 220 m a ltc1387 single 5v rs232/rs485 multiprotocol transceiver configurable as dual rs232 or single rs485 transceiver linear technology corporation 1630 mccarthy blvd., milpitas, ca 95035-7417 (408) 432-1900 l fax: (408) 434-0507 l www.linear-tech.com

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