1 lt1342 5v rs232 transceiver with 3v logic interface s f ea t u re the lt ? 1342 is an advanced low power three-driver, five- receiver rs232 transceiver. the lt1342 operates from a 5v supply and a 3v logic supply. receiver outputs can interface directly to 3v logic circuits. included on the chip is a shutdown pin for reducing supply current to near zero. all receivers and drivers assume high impedance states during shutdown. the driver disable function provides additional control of operating mode. when driver disable is high the charge pump and drivers turn off. receivers continue to operate during driver disable. new esd structures on the chip allow the lt1342 to survive multiple 10kv strikes, eliminating the need for costly transzorbs ? on the rs232 line pins. the lt1342 is fully compliant with all eia rs232 specifi- cations and operates in excess of 120kbaud even driving heavy capacitive loads. n esd protection over 10kv n 3v logic interface n uses small capacitors: 0.1 m f, 0.2 m f n 1 m a supply current in shutdown n low power driver disable operating mode n pin compatible with lt1137a n 120kbaud operation for r l = 3k, c l = 2500pf n 250kbaud operation for r l = 3k, c l = 1000pf n cmos comparable low power: 60mw n operates from a 5v supply and 3v logic supply n easy pc layout: flowthrough architecture n rugged bipolar design n outputs assume a high impedance state when off or powered down n absolutely no latchup d u escriptio , ltc and lt are registered trademarks of linear technology corporation. transzorb is a registered trademark of general instruments, gsi. n notebook computers n palmtop computers u s a o pp l ic at i output waveforms r lt1342 ? ta02 u a o pp l ic at i ty p i ca l receiver output v l = 3v c l = 50pf driver output r l = 3k c l = 2500pf input 1
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5v v cc
driver 1 out
rx1 in
driver 2 out
rx2 in
rx3 in
rx4 in
driver 3 out
rx5 in
on/off
3v v l
driver 1 in
rx1 out
driver 2 in
rx2 out
rx3 out
rx4 out
driver 3 in
rx5 out
v + 0.1 m f 2 0.1 m f 2 0.1 m f 0.1 m f gnd driver disable to line to 3v logic v lt1342 ?ta01 lt1342 nc
2 lt1342 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 order part number 1
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14 v +
5v v cc
c1 +
c1
driver 1 out
rx1 in
driver 2 out
rx2 in
rx3 in
rx4 in
driver 3 out
on/off
3v v l
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c2
c2 +
driver 1 in
rx1 out
driver 2 in
rx2 out
rx3 out
rx4 out
driver 3 in
gnd
nc nw package
28-lead wide pdip top view sw package
28-lead wide plastic so g package
28-lead plastic ssop
rx5 in rx5 out
driver
disable consult factory for industrial and military grade parts. lt1342cg lt1342cnw lt1342csw parameter conditions min typ max units power supply generator v + output 8.6 v v C output C7 v supply current (v cc ) (note 3) 12 17 ma logic supply current (v l ) (note 4) 0.1 1 ma supply current when off (v cc ) shutdown (note 5) l 110 m a driver disable 3 ma logic supply current (v l ) when off shutdown (note 5) l 110 m a driver disable 0.1 1 ma supply rise time c1 = c2 = 0.2 m f, 0.2 ms shutdown to turn-on c + = c C = 0.1 m f on/off pin thresholds input low level (device shutdown) l 1.4 0.8 v input high level (device enabled) l 2.4 1.4 v on/off pin current 0v v on/off 5v l C15 80 m a driver disable pin thresholds input low level (drivers enabled) l 1.4 0.8 v input high level (drivers disabled) l 2.4 1.4 v driver disable pin current 0v v driver disable 5v l C10 500 m a oscillator frequency 130 khz e lectr ic al c c hara terist ics (note 2) t jmax = 125 c, q ja = 96 c/ w (g) t jmax = 125 c, q ja = 56 c/ w (nw) t jmax = 125 c, q ja = 85 c/ w (sw) (note 1) supply voltage (v cc ) ................................................ 6v supply voltage (v l ) .................................................. 6v v + ........................................................................ 13.2v v C ...................................................................... C13.2v input voltage driver ........................................................... v C to v + receiver ................................................ C 30v to 30v output voltage driver .................................................... C 30v to 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
3 lt1342 e lectr ic al c c hara terist ics (note 2) the l denotes specifications which apply over the full operating temperature range (0 c t a 70 c for commercial 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, v l = 3.3v and v on/off = 3v. note 3: supply current is measured with external capacitors c + = c C = 0.1 m f, c1 = c2 = 0.2 m f. all outputs are open with all driver inputs tied high. note 4: v l supply current is measured with all receiver outputs high. note 5: supply current and leakage measurements in shutdown are performed with v on/off 0.1v. supply current measurements using driver disable are performed with v driver disable 3 3v. note 6: 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 7: 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 8: data rate operation guaranteed by slew rate, short-circuit current and propagation delay tests. parameter conditions min typ max units any driver output voltage swing load = 3k to gnd positive l 5 7.3 v negative l C 6.5 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 1.4 v logic input current 0.8v v in 2v l 520 m a output short-circuit current v out = 0v 917 ma output leakage current shutdown, v out = 30v (note 5) l 10 100 m a data rate (note 8) 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 6) 0.6 1.3 m s output transition t lh low to high 0.5 1.3 m s any 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 357 k w output leakage current shutdown (note 4) 0 v out v cc l 110 m a receivers 1 through 4 output voltage output low, i out = C 1.6ma l 0.2 0.4 v output high, i out = 160 m a l 2.7 2.9 v output short-circuit current sinking current, v out = v cc C 20 C10 ma sourcing current, v out = 0v 10 20 ma propagation delay output transition t hl high to low (note 7) 250 600 ns output transition t lh low to high 350 600 ns receiver 5 output voltage output low, i out = C 500 m a l 0.2 0.4 v output high, i out = 160 m a l 2.7 2.9 v output short-circuit current sinking current, v out = v cc C4 C2 ma sourcing current, v out = 0v 2 4 ma propagation delay output transition t hl high to low (note 7) 1 3 m s output transition t lh low to high 1 3 m s
4 lt1342 cc hara terist ics uw a t y p i ca lper f o r c e driver output voltage driver disable threshold supply current in shutdown on/off thresholds driver leakage in shutdown supply current vs data rate temperature (?) ?5 ?0 driver output voltage (v) ? ? ? 0 10 4 0 50 75 lt1342 ?tpc01 ? 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 temperature (?) ?5 0.50 threshold voltage (v) 0.75 1.25 1.50 1.75 3.00 2.25 0 50 75 lt1342 ?tpc02 1.00 2.50 2.75 2.00 ?5 25 100 125 input high input low receiver input thresholds data rate (kbaud) 0 0 supply current (ma) 20 30 40 60 25 50 125 150 lt1342 ?tpc03 70 80 50 10 75 100 3 drivers active
r l = 3k
c l = 2500pf temperature (?) ?5 0 supply current (ma) 2 5 0 50 75 lt1342 ?tpc05 1 4 3 ?5 25 100 125 temperature (?) ?5 threshold voltage (v) 2.0 2.5 3.0 25 75 lt1342 ?tpc06 1.5 1.0 ?5 0 50 100 125 0.5 0 temperature (?) ?5 threshold voltage (v) 2.0 2.5 3.0 25 75 lt1342 ?tpc07 1.5 1.0 ?5 0 50 100 125 0.5 0 on threshold off threshold temperature (?) 0 supply current (ma) 10 15 20 30 lt1341 ?tpc08 35 40 25 5 ?5 0 50 75 ?5 25 100 125 no load 1 driver loaded r l = 3k
2 drivers loaded r l = 3k
3 drivers loaded r l = 3k
supply current temperature (?) 0.1 leakage current ( m a) 10 100 lt1342 ?tpc09 1 ?5 0 50 75 ?5 25 100 125 v out = 30v v out = 30v temperature (?) ?5 supply current ( m a) 100 125 150 25 75 lt1342 ?tpc04 75 50 ?5 0 50 100 125 25 0 supply current in driver disable
5 lt1342 cc hara terist ics uw a t y p i ca lper f o r c e receiver output waveforms receiver short-circuit current driver output waveforms driver output r l = 3k c l = 2500pf input driver output r l = 3k pi fu ctio s u uu 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. v l : 3v logic supply pin. provides power to the receiver outputs. decouple with a 0.1 m f ceramic capacitor. gnd: ground pin. on/off: a ttl/cmos compatible operating mode con- trol. a logic low puts the device in the low power shutdown mode. drivers and receivers assume a high impedance state in shutdown. the transceiver consumes almost no supply current while in shutdown. a logic high fully enables the transceiver. an on/off logic low signal super- sedes the state of the driver disable pin. driver disable: this pin provides an alternate control for the charge pump and rs232 drivers. a logic high on this pin shuts down the charge pump and places all drivers in a high impedance state. all five receivers remain active under these conditions. floating the driver disable pin or driving it to a logic low level fully enables the trans- ceiver. a logic low on the on/off pin supersedes the state of the driver disable pin. supply current drops to 3ma when in driver disable mode. 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 . with multiple transceivers, the v + and v C pins may be paralleled into common charge storage capacitors. larger value capaci- tors may be used to reduce supply ripple. lt1342 ? tpc13 driver short-circuit current rx5 output c l = 50pf rx1 to rx4 output c l = 50pf input lt1342 ? tpc12 v l = 3v temperature ( c) ?5 short-circuit current (ma) 20 25 30 25 75 lt1342 ?tpc10 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 lt1342 ?tpc11 10 40 30 ?5 25 100 125 rx1 to rx4
i sc + rx1 to rx4
i sc rx5 i sc rx5 i sc +
6 lt1342 pi fu ctio s u uu 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. to reduce supply ripple, increase the size of the storage capacitor. c1 + , c1 C , c2 + , c2 C : commutating capacitor inputs. these pins require two external capacitors c 3 0.2 m f: one from c1 + to c1 C , and another from c2 + to c2 C . the capacitors effective series resistance should be less than 2 w . for c 3 1 m f, low esr tantalum capacitors work well in this application, although small value ceramic capacitors may be used with a minimal reduction in charge pump compli- ance. for operation with an external 12v supply, omit c1 and connect the 12v supply to pin c1 + . pin v + may also be shorted to c1 + when a separate supply is used. the 12v supply must be bypassed with a 0.1f capacitor. driver in: rs232 driver input pins. these inputs are compatible with ttl or cmos logic. tie unused inputs to v cc or v l . driver 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 condi- tions up to 2500pf. outputs are in a high impedance state when in shutdown mode, v cc = 0v, or when the driver disable pin is active. outputs are fully short- circuit protected from v C + 30v to v + C 30v. 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 10v for human body model discharges. rx in: 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 immunity. open receiver inputs assume a logic low state. rx out: receiver outputs with 3.3v logic compatible 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 or v l with the power on, off, or in shutdown mode. receiver output level is determined by v l supply voltage. use v l = 3.3v for interfacing with 3.3v logic, v l = 5v for interfacing with 5v logic. esd protectio u the rs232 line inputs of the lt1342 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 lt1342 must be connected to ground through low imped- ances. 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 lt1342 ?esd tc 5v v cc 0.1 m f 0.2 m f 0.1 m f rs232
line pins
protected
to 10kv lt1342 1
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rx1 in
driver 2 out
rx2 in
rx3 in
rx4 in
driver 3 out
rx5 in
3v v l 28
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rx1 out
driver 2 in
rx2 out
rx3 out
rx4 out
driver 3 in
rx5 out v v + 0.1 m f gnd driver disable 0.1 m f nc on/off
7 lt1342 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. package descriptio u dimensions in inches (millimeters) unless otherwise noted. g package 28-lead plastic ssop (0.209) (ltc dwg # 05-08-1640) 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 s28 (wide) 0996 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 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
*
** g28 ssop 0694 0.301 ?0.311
(7.65 ?7.90) 1234 5 6 7 8 9 10 11 12 14 13 0.397 ?0.407*
(10.07 ?10.33)
25 26 22 21 20 19 18 17 16 15 23 24 27 28 0.068 ?0.078
(1.73 ?1.99) 0.002 ?0.008
(0.05 ?0.21) 0.0256
(0.65)
bsc 0.010 ?0.015
(0.25 ?0.38) 0.005 ?0.009
(0.13 ?0.22) 0 ?8 0.022 ?0.037
(0.55 ?0.95) 0.205 ?0.212**
(5.20 ?5.38) dimensions do not include mold flash. mold flash
shall not exceed 0.006" (0.152mm) per side
dimensions do not include interlead flash. interlead
flash shall not exceed 0.010" (0.254mm) per side
*
** n28 1197 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 0.070
(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 0.010
(2.540 0.254) 0.045 ?0.065
(1.143 ?1.651) 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) *these dimensions do not include mold flash or protrusions.
mold flash or protrusions shall not exceed 0.010 inch (0.254mm) nw package 28-lead pdip (wide 0.600) (ltc dwg # 05-08-1520) sw package 28-lead plastic small outline (wide 0.300) (ltc dwg # 05-08-1620)
8 lt1342 ? linear technology corporation 1993 typical applicatio s u operation using 5v and 12v power supplies linear technology corporation 1630 mccarthy blvd., milpitas, ca 95035-7417 (408) 432-1900 l fax: (408) 434-0507 l www.linear-tech.com 1342fa lt/tp 1098 rev a 2k ? printed in usa lt1342 ?ta03 5v v cc 12v v + 0.1 m f to
line lt1342 1
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rx1 in
driver 2 out
rx2 in
rx3 in
rx4 in
driver 3 out
rx5 in
on/0ff = 5v
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rx1 out
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rx2 out
rx3 out
rx4 out
driver 3 in
rx5 out
to logic v v + v cc c1 c1 + 0.1 m f 0.1 m f gnd nc driver disable 0.1 m f related parts part number description comments lt1137a 3-dr/5-rx rs232 transceiver 15kv iec-1000-4-2 esd protection ltc1327 3-dr/5-rx rs562 transceiver 3.3v operation lt1330 3-dr/5-rx rs232 3v logic interface lt1331 3-dr/5-rx rs232/rs562 transceiver 5v rs232 or 3v rs562 operation ltc1347 3-dr/5-rx micropower rs232 transceiver 5 receivers active in shutdown ltc1348 3-dr/5-rx rs232 transceiver true rs232 from 3v typical mouse driving application lt1342 ?ta04 5v v cc 0.1 m f 2 0.1 m f 0.1 m f db9 lt1342 1
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rx1 in
driver 2 out
rx2 in
rx3 in
rx4 in
driver 3 out
rx5 in
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driver 2 in
rx3 out
driver 3 in
mouse v v + logic ? logic ? mouse data logic ? dcd
dsr
rx
rts
tx
cts
dtr
ri (1) (9) (5) logic optics v + v on/off
3v v l rx1 out rx2 out rx4 out rx5 out driver disable
nc gnd
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