1 LT1280A/lt1281a low power 5v rs232 dual driver/receiver with 0.1 m f capacitors r output waveforms LT1280A ? ta02 driver output r l = 3k c l = 2500pf receiver output c l = 50pf input s f ea t u re d u escriptio the lt ? 1280a/lt1281a are dual rs232 driver/receiver pairs with integral charge pump to generate rs232 volt- age levels from a single 5v supply. these circuits feature rugged bipolar design to provide operating fault tolerance and esd protection unmatched by competing cmos designs. using only 0.1 m f external capacitors, these cir- cuits consume only 40mw of power, and can operate to 120kbaud even while driving heavy capacitive loads. new esd structures on the chip allow the LT1280A/lt1281a to survive multiple 10kv strikes, eliminating the need for costly transzorbs ? on the rs232 line pins. the LT1280A/ lt1281a 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 lt1281a is available in 16-pin dip and so packages. the LT1280A is supplied in 18-pin dip and so packages for applications which require shutdown. , ltc and lt are registered trademarks of linear technology corporation. transzorb is a registered trademark of general instruments, gsi n portable computers n battery-powered systems n power supply generator n terminals n modems u s a o pp l ic at i u a o pp l ic at i ty p i ca l 5k 5k 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 LT1280A ta01 LT1280A + + + + n 10ma max supply current n esd protection over 10kv 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 available in so package
2 LT1280A/lt1281a 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 LT1280Ac/lt1281ac ............................. 0 c to 70 c LT1280Ai/lt1281ai .......................... 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 order part number order part number (note 2) e lectr ic al c c hara terist ics consult factory for military grade parts. 1
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nc
c1 +
v +
c1
c2 +
c2
v
tr2 out
rec2 in n package 18-lead pdip
sw package
18-lead plastic so wide on/off
v cc
gnd
tr1 out
rec1 in
rec1 out
tr1 in
tr2 in
rec2 out
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) LT1280Acn LT1280Ain LT1280Acsw LT1280Aisw 1
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8 top view 16
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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 pdip
sw package
16-lead plastic so wide
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 = 27 c/w (sw) lt1281acn lt1281ain lt1281acsw lt1281aisw (note 1) 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 c 8 10 ma l 14 ma supply current when off (v cc ) shutdown (note 4) LT1280A only l 110 m a supply rise time c1 = c2 = c3 = c4 = 0.1 m f 0.2 ms shutdown to turn-on LT1280A 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 5.0 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
3 LT1280A/lt1281a driver output voltage temperature (?) ?5 ?0 driver output voltage (v) ? ? ? 0 10 4 0 50 75 LT1280A ?tpc03 ? 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 cc hara terist ics uw a t y p i ca lper f o r c e 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 917 ma output leakage current shutdown v out = 30v (note 4) l 10 100 m a data rate (note 7) 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) c grade l 0.8 1.3 v input high threshold (v out = low) c grade l 1.7 2.4 v input low i grade l 0.2 1.3 v input high i grade l 1.7 3.0 v hysteresis l 0.1 0.4 1.0 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 C20 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). note 7: data rate operation guaranteed by slew rate, short-circuit current and propagation delay tests. the l denotes specifications which apply over the operating temperature range (0 c t a 70 c for commercial grade, and C 40 c t a 85 c for industrial grade. 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. 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 LT1280A ?tpc01 10 13579 20k baud 60k baud 120k baud driver minimum output voltage vs load capacitance load capacitance (nf) 0 7.0 peak output voltage (v) 6.5 6.0 5.5 5.0
4.5 4.0 2468 LT1280A ?tpc02 10 13579 120k baud 60k baud 20k baud
4 LT1280A/lt1281a cc hara terist ics uw a t y p i ca lper f o r c e receiver input thresholds driver leakage in shutdown on/off thresholds receiver short-circuit current slew rate vs load capacitance temperature (?) ?5 0.50 threshold voltage (v) 0.75 1.25 1.50 1.75 3.00 2.25 0 50 75 LT1280A ?tpc04 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 LT1280A ?tpc05 125 150 2 drivers active
r l = 3k
c l = 2500pf supply current vs data rate temperature (?) ?5 threshold voltage (v) 2.0 2.5 3.0 25 75 LT1280A ?tpc06 1.5 1.0 ?5 0 50 100 125 0.5 0 on threshold off threshold supply current temperature (?) ?5 0 supply current (ma) 10 25 0 50 75 LT1280A ?tpc07 5 20 15 ?5 25 100 125 2 drivers loaded r l = 3k 1 driver loaded r l = 3k no load driver short-circuit current load capacitance (nf) 0 slew rate (v/?) 12 16 4.0 LT1280A ?tpc11 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 temperature (?) 0.1 leakage current ( m a) 10 100 LT1280A ?tpc08 1 ?5 0 50 75 ?5 25 100 125 v out = 30v v out = 30v temperature ( c) ?5 short-circuit current (ma) 20 25 30 25 75 LT1280A ?tpc09 15 10 ?5 0 50 100 125 5 0 i sc + i sc temperature ( c) ?5 0 short-circuit current (ma) 20 50 0 50 75 LT1280A ?tpc10 10 40 30 ?5 25 100 125 rx i sc rx i sc +
5 LT1280A/lt1281a cc hara terist ics uw a t y p i ca lper f o r c e shutdown to driver outputs driver output waveforms LT1280A ? tpc13 LT1280A ? tpc12 pi fu ctio s u uu 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 10kv for human body model 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 10kv for human body model discharges. each receiver provides 0.4v of hysteresis for noise immunity. open receiver inputs assume a logic low 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. out- puts 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 . 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 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 LT1280A 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 capaci- tor c 3 0.1 m f, tied to ground or v cc . larger value capaci- tors 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 transceivers, 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.
6 LT1280A/lt1281a esd protectio u the rs232 line inputs of the LT1280A/lt1281a have on- chip protection 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 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. esd test circuit 1280a esd tc 0.1 m f rs232
line pins
protected
to 10kv 1
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10 0.1 m f 0.1 m f 0.1 m f nc c1 + v + c1 c2 + c2 v dr2 out LT1280A 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 10kv rx2 in rx2 out + + + + + 5
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9 u a o pp l ic at i ty p i ca l supporting an lt1039 (triple driver/receiver) 30k 30k rs232 output rs232 output rs232 input rs232 input LT1280A 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 LT1280A 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 + + + +
7 LT1280A/lt1281a package descriptio u dimensions in inches (millimeters) unless otherwise noted. 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. 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
*
** sw package 16-lead plastic small outline (wide 0.300) (ltc dwg # 05-08-1620) n package 16-lead pdip (narrow 0.300) (ltc dwg # 05-08-1510) n16 1197 0.770*
(19.558)
max 16 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 0.255 0.015*
(6.477 0.381) 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) n package 18-lead pdip (narrow 0.300) (ltc dwg # 05-08-1510) n18 1197 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 0.020
(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) 0.009 ?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)
8 LT1280A/lt1281a package descriptio u dimensions in inches (millimeters) unless otherwise noted. ? linear technology corporation 1993 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
*
** u a o pp l ic at i ty p i ca l 12801afa lt/tp 1098 rev a 2k ? printed in usa 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 LT1280A ta03 LT1280A 12v input + + operation using 5v and 12v power supplies part number description comments lt1180a/lt1181a 5v 2-driver/2-receiver rs232 transceivers pin compatible with LT1280A/LT1280A lt1381 5v 2-driver/2-receiver rs232 transceiver narrow 16-pin so package lt1780/lt1781 5v 2-driver/2-receiver rs232 transceiver iec 1000-4-2 level 4 compliance related parts 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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