1 l t c1 3 1 8 single 5v rs232/rs422/applet alk dce t ransceiver descriptio n u n dual-mode rs232/rs422 peripherals n appletalk peripherals n single 5v systems applicatio n s u the ltc 1318 is a single 5v, rs232/rs422 transceiver for connection to the dce, or peripheral side of an interface link. it includes an on-board charge pump to generate a 8v supply which allows true rs232 output swings. the charge pump requires only four external 0.1 m f capacitors. the ltc1318 includes two rs232 drivers, a differential rs422 driver, a dedicated rs232 receiver, and a pin selectable rs232/rs422 receiver which can receive either single-ended or differential signals. the ltc1318 features driver outputs which can be taken to common-mode voltages outside the power supply rails without damage. additionally, the driver outputs assume a high impedance state when the power is shut off, preventing externally applied signals from feeding back into the power supplies. the rs232 devices will operate at speeds up to 100kbaud. the rs422 devices will operate up to 2mbaud. the ltc1318 is available in a 24-lead so wide package. n single chip provides dce rs232 or rs422/appletalk dce port n operates from a single 5v supply n charge pump uses 0.1 m f capacitors n output common-mode voltage range exceeds power supply rails for all drivers n driver outputs are high impedance with power off n pin selectable rs232/rs422 receiver n thermal shutdown protection n drivers are short-circuit protected features , ltc and lt are registered trademarks of linear technology corporation. appletalk and localtalk are registered trademarks of apple computer, inc. typical applicatio n s u charge pump rs232 lines appletalk network localtalk transformer 100pf 4 22 w 22 w 22 w 22 w 22 w 22 w 22 w 22 w v + c1 + c1 rxi1 txo1 txo2 v cc rxd + rxd /rxi2 txd + txd nc v c2 c2 + rxo1 txi1 txi2 gnd rxdo/rxo2 txd rxmode gnd nc 0.1 m f 0.1 m f 0.1 m f rs232 rs232 rs232 rs422 rs422 5v 1k 1k 0.1 m f ltc1318 to digital system lt1318 ta01 rs232 r l = 100 w 200ns/div 1318 ta02 c l = 100pf driver output waveforms txd (5v/div) txd + , txd (2v/div) rxdo (5v/div) for information purposes only obsolete: contact linear technology for potential replacement
2 ltc1318 absolute m axi m u m ratings w ww package/order i n for m atio n w uu supply voltage: v cc ...................................................................................... 7v v + ................................................................................... 13.2v v C ............................................................................... C 13.2v input voltage: all drivers .............................. C 0.3 to (v cc + 0.3v) all receivers ...................................... C 25v to 25v rxmode pin ....................... C 0.3v to (v cc + 0.3v) output voltage: rs232 drivers ................ (v + C 30v) to (v C + 30v) rs422 drivers ................................................ 15v all receivers ........................ C 0.3v to (v cc + 0.3v) short-circuit duration: v + or v C to gnd .......................................... 30 sec driver or receiver outputs ...................... indefinite operating temperature range .................... 0 c to 70 c lead temperature (soldering, 10 sec)................. 300 c (note 1) electrical characteristics consult factory for industrial and military grade parts symbol parameter conditions min typ max units supplies i cc supply current no load l 930 ma v + positive charge pump output voltage i out = 0ma l 7.8 8.8 v i out = 10ma, v cc = 5v l 6.8 7.4 v v C negative charge pump output voltage i out = 0ma l C7.3 C8.6 v i out = C 5ma, v cc = 5v l C 6.3 C7.3 v differential driver v od differential driver output voltage no load (figure 1) l 4v r l = 100 w (figure 1) l 2v dv od change in magnitude of differential r l = 100 w (figure 1) l 0.2 v output voltage v oc common-mode output voltage r l = 100 w (figure 1) l 3v i dss short-circuit output current C 1v < v cmr < 7v l 35 200 ma v il input low voltage l 0.8 v v ih input high voltage l 2.0 v single-ended driver v o output voltage swing r l = 3k l 5 7.3/C6.5 v i oss short-circuit output current v out = ov l 5 17 ma v il input low voltage l 0.8 v v ih input high voltage l 2v sr output slew rate r l = 3k, c l = 51pf l 42030 v/ m s t jmax = 125 c, q ja = 85 c/w v s = 5v 5%, c1 = c2 = 0.1 m f, t a = 0 c to 70 c, unless otherwise specified. (notes 2, 3) 1
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12 top view sw package
24-lead plastic so wide 24
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v +
c1 +
c1
rxi1
txo1
txo2
v cc
rxd +
rxd /rxi2
txd +
txd
nc v
c2
c2 +
rxo1
txi1
txi2
gnd
rxdo/rxo2
txd
rxmode
gnd
nc
order part number ltc1318csw
3 ltc1318 electrical characteristics symbol parameter conditions min typ max units differential receiver v th differential receiver threshold l C 0.2 0.2 v cmr common-mode input range l C7 7 v hysteresis v cm = ov l 30 mv r in input resistance ta = 25 c 357 k w v ol output low voltage i out = C1.6ma 0.4 v v oh output high voltage i out = 160 m a, v cc = 5v l 3.5 v i oss short-circuit output current v o = gnd or v cc l 7 85 ma single-ended receiver v l input voltage low threshold l 0.8 1.4 v v ih input voltage high threshold l 1.8 2.4 v hysteresis l 0.1 0.4 1.0 v r in input resistance ta = 25 c 357 k w v ol output low voltage i out = C4ma l 0.2 0.4 v v oh output high voltage i out = 4ma, v cc = 5v l 3.5 4.8 C v i oss short-circuit output current v o = gnd or v cc l 7 85 ma v ilrxm rxmode input low voltage l 0.8 1.6 v v ihrxm rxmode input high voltage l 1.6 2.0 v i inrxm rxmode input current v in = ov or v cc l 2 m a switching characteristics t plh,hl differential driver propagation delay r l = 100 w , c l = 100pf (figures 2,3) l 35 100 ns t skew differential driver output to output r l = 100 w , c l = 100pf (figures 2,3) l 535 ns t r,f differential driver rise, fall time r l = 100 w , c l = 100pf (figures 2,3) l 15 50 ns t plh,hl differential receiver propagation delay c l = 15pf, (figures 4) l 110 200 ns t sel receiver mode switching time l 25 100 ns 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: all currents into device pins are negative, all currents out of device pins are positive. all voltages are referenced to ground unless otherwise specified. note 3: all typicals are given at v cc = 5v, t a = 25 c. v s = 5v 5%, c1 = c2 = 0.1 m f, t a = 0 c to 70 c, unless otherwise specified. (notes 2, 3)
4 ltc1318 typical perfor m a n ce characteristics uw load current (ma) 0 charge pump output voltage (v) 10
8
6
4
2
0
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10
12 1318 g02 3 6 9 15 v + v t a = 25 c
v cc = 5v
i load = v + to v temperature ( c) 0 supply current (ma) 10.0
9.8
9.6
9.4
9.2
9.0
8.8
8.6
8.4
8.2
8.0 20 40 50 1318 g01 10 30 60 70 v cc = 5v charge pump output voltage vs load current temperature ( c) 0 threshold voltage (v) 60 1318 g03 20 40 2.4
2.2
2.0
1.8
1.6
1.4
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0.8 10 30 50 70 v cc = 5v input high (txi1, txi2) input high (txd) input low (txd) input low (txi1, txi2) ttl input threshold vs temperature rs422 driver single-ended output swing vs load current supply current vs temperature rs422 driver short-circuit current vs temperature load current (ma) 0 differential output swing (v) 10
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1
0
1318 g04 10
20 30 40 50 60 70 80 90 100 t a = 25 c
v cc = 5v
i load from
txd + to txd
load current (ma) 0 driver output swing (v) 5.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
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1318 g05 10
20 30 40 50 60 70 80 90 100 t a = 25 c
v cc = 5v
i load from txd + ,
txd ? to gnd temperature ( c) 0 short-circuit current (ma) 100
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80 20 40 50 1318 g06 10 30 60 70 v cc = 5v i sc + i sc rs422 driver differential output swing vs load current rs232 driver output swing vs resistive load rs232 driver slew rate vs load capacitance rs232 driver short-circuit current vs temperature resistive load (k w ) 1 driver output swing (v) 10
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?0 310 1318 g08 245 6 78 9 t a = 25 c
v cc = 5v positive swing negative swing capacitance (pf) 10 slew rate (v/ m s) 25
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0 100 1000 10000 1318 g07 sr sr + t a = 25 c
v cc = 5v temperature ( c) 0 short-circuit current (ma) 20.0
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15.0 20 40 50 1318 g09 10 30 60 70 v cc = 5v i sc + i sc
5 ltc1318 typical perfor m a n ce characteristics uw temperature ( c) 0 threshold voltage (mv) 60 1318 g10 20 40 100
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10 30 50 1318 g12 10 20 40 60 70 short-circuit current (ma) rxo1 v cc = 5v rxdo/rxo2 temperature ( c) 0 threshold voltage (v) 60 1318 g11 20 40 2.4
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0.8 10 30 50 70 input high (rxdo/rxo2) input high (rxo1) input low (rxo1) v cc = 5v input low (rxdo/rxo2) ttl output short-circuit current vs temperature rs232 receiver input threshold vs temperature v + (pin 1): charge pump positive output. this pin re- quires a 0.1 m f capacitor to ground. under normal opera- tion this pin maintains a voltage of about 8.8v above ground. an external load can be connected between this pin and ground or v C . c1 + , c1 C (pins 2, 3): c1 inputs. connect a 0.1 m f capacitor between c1 + and c1 C . rxi1 (pin 4): first rs232 single-ended receiver input. this is an inverting receiver. txo1, txo2 (pins 5,6): rs232 single-ended driver out- puts. v cc (pin 7): positive supply input. apply 4.75v v cc 5.25v to this pin. a 0.1 m f bypass capacitor is required. rxd + (pin 8): when rxmode (pin 15) is low, this pin acts as the differential rs422 receiver positive input. when rxmode is high, this pin is disabled. rxd C /rxi2 (pin 9): when rxmode (pin 15) is low, this pin acts as the differential rs422 receiver negative input. when rxmode is high, this pin acts as the second rs232 receiver input. the receiver is inverting in rs232 mode. txd + (pin 10): differential rs422 driver noninverting output. pi n fu n ctio n s uuu txd C (pin 11): differential rs422 driver inverting output. nc (pins 12,13): no internal connection. gnd (pins 14, 18): power supply ground. connect both pins to each other and to the ground. rxmode (pin 15): this pin controls the state of the differential/single-ended receiver. when rxmode is low, the receiver is in differential mode and will receive rs422 compatible signals at rxd + and rxd C /rxi2 (pins 8 and 9). when rxmode goes high, the receiver enters single-ended mode and will receive rs232 compatible signals at rxd C /rxi2. rxd + is disabled in single-ended mode. both modes use the rxdo/rxo2 pin (pin 17) as their output. txd (pin 16): differential rs422 driver input (ttl com- patible). rxdo/rxo2 (pin 17): this is the output of the configurable differential/single-ended receiver. txi1, txi2 (pins 20, 19): rs232 driver inputs (ttl compatible). both are inverting inputs. rxo1 (pin 21): first rs232 receiver outputs (ttl com- patible). rs422 receiver differential threshold vs temperature
6 ltc1318 pi n fu n ctio n s uuu c2 + , c2 C (pins 22, 23): c2 inputs. connect a 0.1 m f capacitor between c2 + and c2 C . v C (pin 24): charge pump negative output. this pin requires a 0.1 m f capacitor to ground. under normal opera- tion, this pin maintains a voltage of about 8.6v below ground. an external load can be connected between this pin and ground or v + . 1318 f01 v od v oc + + txd txd + txd r l /2 r l /2 figure 1. figure 2. 1318 f02 txd c l c l c l txd + rxd + rxd0/rxd2 rxd /
rxi2 txd r d test circuits
figure 4. differential receiver v od2 (rxd + ) ?(rxd ) rxdo v ol v oh lt1318 ?f04 t plh t phl ? od2 1.5v 1.5v f = 1mhz: t r 10ns: t f 10ns 1.5v 3v 0v txd f = 1mhz: t r 10ns: t f 10ns 1.5v ? o v o t skew 1/2 v o lt1318 ?f03 t plh t r 90% 50% 10% t phl t f 90% 50% 10% v o t skew v diff = v(txd + ) ?v(txd ) txd txd + figure 3. differential driver switchi n g wavefor m s u w
7 ltc1318 to the c1 + /c1 C and c2 + /c2 C pins, and two hold caps, one from v + to ground and one from v C to ground. the charge pump has enough extra capacity to drive light external loads and still meet rs232 specifications; it will support a 10ma load from v + to ground or a 5ma from v + to v C (figure 5). interface standards the ltc1318 provides compatibility with both rs232 and rs422/appletalk/localtalk standards in a single chip, enabling a system to communicate using either protocol as necessary. the ltc1318 provides two rs232 single- ended drivers, one rs422 differential driver, and two receivers. one of the receivers is a dedicated rs232 single-ended receiver, while the other can be configured for rs232 (single-ended) or rs422 (differential) opera- tion by controlling the logic state of the select pin. all single-ended drivers and receivers meet the rs232c specification for output swing, load driving capacity and input range, and can additionally transmit and receive signals as high as 100kbaud. the differential driver and receiver can interface to both rs422 and appletalk net- works, and can transmit and receive signals at rates exceeding 2mbaud. fault protection the ltc1318 incorporates many protection features to make it as bustproof as possible. all driver outputs and receiver inputs are protected against esd strikes to 6kv, eliminating the need for external protection devices in most applications. all driver outputs can be taken outside the power supply rails without damage and will not allow current to be forced back into the supplies, preventing the output fault from affecting other logic circuits using the same power supply. additionally, the driver outputs enter a high impedance state when the power is removed, preventing the system from loading the data lines when it is shut off. all driver and receiver outputs are protected against short circuits to ground or to the supply rails. charge pump power supply the ltc1318 includes an on-board charge pump to gen- erate the voltages necessary for true rs232 compatible output swing. this charge pump requires just four exter- nal 0.1 m f capacitors to operate; two flying caps connected 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. figure 5. configurable rs422/rs232 receiver there are two line receivers in the ltc1318. one is a dedicated rs232 receiver; the other can receive both single-ended rs232 signals and differential rs422 sig- nals. this second receiver has two inputs: rxd + (pin 8) and rxd C (pin 9) to accept differential signals. the rxd + input is disabled in single-ended mode. the receiver mode is set by the rxmode (pin 15). a low level on rxmode configures the receiver in differential mode; it accepts input at rxd + and rxd C and outputs the data at rxdo (pin 17). a high level at rxmode forces the receiver into single-ended mode; rxd + is disabled, pin 9 switches identity from rxd C to rxi2, and pin 17 switches from rxdo to rxo2, the single-ended data output. in this mode the receiver accepts rs232 signals at rxi2 and outputs the data through rxo2. the receiver becomes inverting in single-ended mode. this receiver can switch between its two modes within 100ns, allowing the system to sense the input signal and configure itself accordingly. external
device 1 0.1 m f 0.1 m f 0.1 m f 0.1 m f lt1318 ?f05 24 23 22 3 2 5v v + v 8v at 5ma 7v at 5ma ltc1318 applicatio n i n for m atio n wu u u
8 ltc1318 linear technology corporation 1630 mccarthy blvd., milpitas, ca 95035-7487 (408) 432-1900 l fax : (408) 434-0507 l telex : 499-3977 ? linear technology corporation 1995 lt/gp 0295 10k ? printed in usa package descriptio n u dimensions in inches (millimeters) unless otherwise noted. s package 24-lead plastic sol sol24 0392 note 1 0.598 ?0.614
(15.190 ?15.600)
(note 2) 22 21 20 19 18 17 16 15 1 23 4 5 6 78 0.394 ?0.419
(10.007 ?10.643) 910 13 14 11 12 23 24 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) 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)
(note 2) 45 0.010 ?0.029
(0.254 ?0.737) 0.005
(0.127)
rad min 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. 2. these dimensions do not include mold flash or protrusions.
mold flash or protrusions shall not exceed 0.006 inch (0.15mm).
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