1 lt1381 low power 5v rs232 dual driver/receiver with 0.1 m f capacitors r output waveforms driver output r l = 3k c l = 2500pf receiver output c l = 50pf input u s a o pp l ic at i n portable computers n battery-powered systems n power supply generator n terminals n modems u a o pp l ic at i ty p i ca l d u escriptio s f ea t u re n esd protection over 10kv n low cost n uses small capacitors: 0.1 m f n cmos comparable low power: 40mw n operates from a single 5v supply n 120kbaud operation for r l = 3k, c l = 2500pf n 250kbaud operation for r l = 3k, c l = 1000pf n rugged bipolar design n outputs assume a high impedance state when powered down n absolutely no latchup n available in narrow so package 5k 5k 0.1 f logic inputs logic outputs 9 12 10 11 5 4 3 1 15 8 13 7 14 6 2 16 5v input v + out v out rs232 output rs232 output rs232 input rs232 input lt1381 ta01 lt1381 0.1 f 0.1 f 0.1 f + + + + s , ltc and lt are registered trademarks of linear technology corporation. transzorb ? is a registered trademark of general instruments, gsi the lt ? 1381 is a dual rs232 driver/receiver pair with integral charge pump to generate rs232 voltage levels from a single 5v supply. the circuit features rugged bipolar design to provide operating fault tolerance and esd protection unmatched by competing cmos designs. using only 0.1 m f external capacitors, the circuit con- sumes only 40mw of power and can operate to 120kbaud even while driving heavy capacitive loads. new esd struc- tures on the chip allow the lt1381 to survive multiple 10kv strikes, eliminating the need for costly transzorbs ? on the rs232 line pins. driver outputs are protected from overload and can be shorted to ground or up to 25v without damage. during power-off conditions, driver and receiver outputs are in a high impedance state, allowing line sharing. lt1381 ? ta02
2 lt1381 a u g w a w u w a r b s o lu t exi t i s wu u package / o rder i for atio (note 1) supply voltage (v cc ) ................................................ 6v v + ........................................................................ 13.2v v C ...................................................................... C13.2v input voltage driver ........................................................... v C to v + receiver ............................................... C 30v to 30v 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 lt1381c ................................................. 0 c to 70 c lt1381i .............................................. C 40 c to 85 c storage temperature range ................ C 65 c to 150 c lead temperature (soldering, 10 sec)................. 300 c order part number lt1381cn lt1381cs lt1381is 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 soic t jmax = 125 c, q ja = 90 c/ w, q jc = 46 c/w (n) t jmax = 125 c, q ja = 110 c/ w, q jc = 34 c/w (s) consult factory for military grade parts. (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 C 7.0 v supply current (v cc ) (note 3), t a = 25 c814ma l 16 ma supply rise time c1 = c2 = c3 = c4 = 0.1 m f 0.2 ms 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 5.0 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 logic input current 0.8v v in 2.0v l 520 m a output short-circuit current v out = 0v 9 17 ma output leakage current power off v out = 15v 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 6 v/ m s propagation delay output transition t hl high to low (note 4) 0.6 1.3 m s output transition t lh low to high 0.5 1.3 m s
3 lt1381 parameter conditions min typ max units 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 1.0 v input resistance (note 6) 3 5 7 k w 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 5) 250 600 ns output transition t lh low-to-high 350 600 ns e lectr ic al c c hara terist ics (note 2) typical perfor a ce characteristics wu driver maximum output voltage vs load capacitance temperature (?) ?5 ?0 driver output voltage (v) ? ? ? 0 10 4 0 50 75 lt1381 ?tpc03 ? 6 8 2 ?5 25 100 125 r l = 3k v cc = 5.5v v cc = 5v v cc = 4.5v v cc = 4.5v v cc = 5v v cc = 5.5v output high output low driver minimum output voltage vs load capacitance driver output voltage note 4: 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 5: 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). note 6: tested at v in = 10v. the l denotes specifications which apply over the full 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, 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 load capacitance (nf) 7.0 peak output voltage (v) 6.0 5.0 4.0 2468 lt1381 ?tpc02 10 13579 5.5 4.5 6.5 0 2 drivers loaded 120k baud 60k baud 20k baud load capacitance (nf) 0 peak output voltage (v) 8.0 9.0 8 lt1381 ?tpc01 7.0 6.0 5.0 2 4 6 10 7.5 8.5 6.5 5.5 7 1 3 5 9 2 drivers loaded 20k baud 60k baud 120k baud
4 lt1381 typical perfor a ce characteristics wu temperature (?) ?5 0.50 threshold voltage (v) 0.75 1.25 1.50 1.75 3.00 2.25 0 50 75 lt1381 ?tpc04 1.00 2.50 2.75 2.00 ?5 25 100 125 input high input low receiver input threshold supply current vs data rate data rate (kbaud) 0 0 supply current (ma) 10 20 30 40 50 25 50 75 100 lt1381 ?tpc05 125 150 2 drivers active r l = 3k c l = 2500pf driver leakage in shutdown temperature (?) 0.1 leakage current ( m a) 10 100 lt1381 ?tpc06 1 ?5 0 50 75 ?5 25 100 125 v out = 30v v out = 30v receiver short-circuit current temperature (?) ?5 0 short-circuit current (ma) 20 50 0 50 75 ltlt1381 ?tpc07 10 40 30 ?5 25 100 125 isc isc + driver short-circuit current slew rate vs load capacitance v + compliance curve load current + (ma) 0 0 v + (v) 2 4 6 8 10 510 lt1381 ?tpc10 15 v + (0.1 m f) v + (1 m f) temperature (?c) ?5 short-circuit current (ma) 20 25 30 25 75 lt1381 ?tpc08 15 10 ?5 0 50 100 125 5 0 isc + isc capacitance (nf) 0 slew rate (v/ m s) 12 16 20 4 lt1381 ?tpc09 8 4 0 1 2 3 5 10 14 18 6 2 +slew rate slew rate v C compliance curve load current (ma) 0 0 v (v) ? ? ? ? ?0 510 lt1381 ?tpc11 15 v (0.1 m f) v (1 m f)
5 lt1381 pi fu ctio s u uu c1 + , c1 C , c2 + , c2 C (pins 1, 3, 4, 5): commutating capacitor inputs. these pins require two external capaci- tors c 3 0.1 m f: one from c1 + to c1 C and another from c2 + to c2 C . c1 may be deleted if a separate 12v supply is available and connected to pin c1 + . v + (pin 2): positive supply output (rs232 drivers). v + ? 2v cc C 2.1v. 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 (pin 6): negative supply output (rs232 drivers). v C ? C(2v cc C 3v). 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. tr2 out, tr1 out (pin 7, 14): 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 v cc = 0v. outputs are fully short- circuit protected from v C + 25v to v + C 25v. applying higher voltages will not damage the device if the over- drive 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 10kv for human body model discharges. rec2 in, rec1 in (pins 8, 13): receiver inputs. these pins accept rs232 level signals ( 30v) into a protected 5k terminating resistor. the receiver inputs are protected against esd to 10kv for human body model discharges. each receiver provides 0.4v of hysteresis for noise immu- nity. open receiver inputs assume a logic low state. rec2 out, rec1 out (pins 9, 12): receiver outputs with ttl/cmos voltage levels. outputs are fully short-circuit protected to ground or v cc with the power on or off. tr2 in, tr1 in (pins 10, 11): rs232 driver input pins. these inputs are ttl/cmos compatible. inputs should not be allowed to float. tie unused inputs to v cc . gnd (pin 15): ground pin. v cc (pin 16): 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. esd protectio u the rs232 line inputs of the lt1381 have on-chip protec- tion from esd transients up to 10kv. 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 impedance in normal application of the circuit. the only constraint is that low esr capacitors must be used for bypassing and charge storage. esd testing must be done with pins v cc , v + , v C and gnd shorted to ground or connected with low esr capacitors. esd test circuit lt1381 ?esd tc 0.1 f rs232 line pins protected to 10kv 1 2 3 4 5 6 7 8 16 15 14 13 12 11 10 9 0.1 f 0.1 f 0.1 f c1 + v + c1 c2 + c2 v tr2 out lt1381 0.1 f 5v v cc gnd tr1 out rec1 in rec1 out tr1 in tr2 in rs232 line pins protected to 10kv rec2 in rec2 out + + + + +
6 lt1381 typical applicatio s u isolated rs232 driver/receiver i lim lt1111 fb sw2 v in sw1 gnd 1n5818 l1 20 m h ctx20-1 1:1 47 10k 1k 1n5818 100 f 1 lt1121-5 100 f v in = 5v 10% from system 5v 10% v cc gnd1 in gnd2 13.7v lt1381 rs232 gnd2 os gnd1 v cc os in 1 3 4 5 16 2 6 98 11 14 rs232 input rs232 output v out v in isolator output (data to system) isolator input (data from system) ltc1145 ltc1145 isolation barrier floating ground lt1381 ?ta03 r x d x v cc 15 system ground + + 10 f + 0.1 f + 0.1 f + 0.1 f + 0.1 f + 1 f 0.1 f + isolator output rs232 input isolator input rs232 output data transmission across isolation barrier 1381 ta04 1381 ta05
7 lt1381 package descriptio u dimensions in inches (millimeters) unless otherwise noted. n package 16-lead pdip (narrow 0.300) (ltc dwg # 05-08-1510) 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) 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 * ** s package 16-lead plastic small outline (narrow 0.150) (ltc dwg # 05-08-1610) 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 circuits as described herein will not infringe on existing patent rights.
8 lt1381 ? linear technology corporation 1993 typical applicatio s u related parts 1381fa, sn1381 lt/tp 1098 rev a 2k ? printed in usa part number description comments lt1180a/lt1181a 5v 2-driver/2-receiver rs232 transceivers pin compatible with lt1280a/lt1280a lt1280a/lt1281a 5v 2-driver/2-receiver rs232 transceivers pin compatible with lt1180a/lt1181a lt1780/lt1781 5v 2-driver/2-receiver rs232 transceivers iec 1000-4-2 level 4 compliance operation using 5v and 12v power supplies sharing capacitors 16 11 10 12 2 14 13 98 14 5k 5k 6 7 5 3 v + v rs232 output rs232 output rs232 input rs232 input c2 + c2 c1 c1 + ttl output ttl output ttl input ttl input 5v v cc lt1381 lt1381 ?ta07 0.1 f + 0.1 f + + + 16 11 10 12 2 14 13 98 14 5k 5k 6 7 5 3 v + v rs232 output rs232 output rs232 input rs232 input c2 + c2 c1 c1 + ttl output ttl output ttl input ttl input 5v v cc lt1381 0.1 f 0.1 f + 0.1 f + 5k 5k s logic inputs logic outputs 9 12 10 11 5 4 2 1 15 8 13 7 14 16 3 16 5v input 12v out rs232 output rs232 output rs232 input rs232 input lt1381 ta06 lt1381 12v input 0.1 f + 0.1 f + 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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