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lt1785/lt1785a/ lt1791/lt1791a 1 178591fc typical application description 60v fault protected rs485/rs422 transceivers the lt ? 1785/lt1791 are half-duplex and full-duplex differ- ential bus transceivers for rs485 and rs422 applications which feature on-chip protection from overvoltage faults on the data transmission lines. receiver input and driver output pins can withstand voltage faults up to 60v with respect to ground with no damage to the device. faults may occur while the transceiver is active, shut down or powered off. data rates to 250kbaud on networks of up to 128 nodes are supported. controlled slew rates on the driver out- putscontrol emi emissions and improve data transmis- sion integrity on improperly terminated lines. drivers are speci? ed to operate with inexpensive cables as low as 72 characteristic impedance. the lt1785a/lt1791a devices have fail-safe receiver inputs to guarantee a receiver output high for shorted, open or inactive data lines. on-chip esd protection eliminates need for external protection devices. the lt1785/lt1785a are available in 8-lead dip and so packages and the lt1791/lt1791a in 14-lead dip and so packages. normal operation waveforms at 250kbaud l , lt, ltc and ltm are registered trademarks of linear technology corporation. all other trademarks are the property of their respective owners. features applications n protected from overvoltage line faults to 60v n pin compatible with ltc485 and ltc491 n high input impedance supports up to 128 nodes n no damage or latchup to esd iec-1000-4-2 level 4: 15kv air discharge iec-1000-4-2 level 2: 4kv contact discharge n controlled slew rates for emi emissions control n guaranteed high receiver output state for floating, shorted or inactive inputs n outputs assume a high impedance when off or powered down n drives low cost, low impedance cables n short-circuit protection on all outputs n thermal shutdown protection n guaranteed operation to 125c n industrial control data networks n can bus applications n hvac controls gnd1 gnd2 r term 178591 ta01 ro1 re 1 de1 di1 lt1785 ro2 re 2 de2 di2 lt1785 v cc1 v cc2 r term tx tx rx rx ro 178591 ta02 di y-z
lt1785/lt1785a/ lt1791/lt1791a 2 178591fc absolute maximum ratings (note 1) 1 2 3 4 8 7 6 5 top view v cc b a gnd n8 package 8-lead pdip s8 package 8-lead plastic so r d ro re de di t jmax = 150c, ja = 130c/w (n8) t jmax = 150c, ja = 150c/w (s8) top view n package 14-lead pdip s package 14-lead plastic so 1 2 3 4 5 6 7 14 13 12 11 10 9 8 nc ro re de di gnd gnd v cc nc a b z y nc r d t jmax = 150c, ja = 130c/w (n) t jmax = 150c, ja = 150c/w (s) pin configuration order information lead free finish tape and reel part marking* package description temperature range lt1785cn8#pbf lt1785cn8#trpbf 1785 8-lead pdip 0c to 70c lt1785cs8#pbf lt1785cs8#trpbf 1785 8-lead plastic so 0c to 70c lt1785in8#pbf lt1785in8#trpbf 1785i 8-lead pdip C40c to 85c lt1785is8#pbf lt1785is8#trpbf 1785i 8-lead plastic so C40c to 85c lt1785acn8#pbf lt1785acn8#trpbf 1785a 8-lead pdip 0c to 70c lt1785acs8#pbf lt1785acs8#trpbf 1785a 8-lead plastic so 0c to 70c lt1785ain8#pbf lt1785ain8#trpbf 1785ai 8-lead pdip C40c to 85c lt1785ais8#pbf lt1785ais8#trpbf 1785ai 8-lead plastic so C40c to 85c lt1785hn8#pbf lt1785hn8#trpbf 1785h 8-lead pdip C40c to 125c lt1785hs8#pbf lt1785hs8#trpbf 1785h 8-lead plastic so C40c to 125c lt1785ahn8#pbf lt1785ahn8#trpbf 1785ah 8-lead pdip C40c to 125c lt1785ahs8#pbf lt1785ahs8#trpbf 1785ah 8-lead plastic so C40c to 125c lt1791cn#pbf lt1791cn#trpbf 1791 14-lead pdip 0c to 70c lt1791cs#pbf lt1791cs#trpbf 1791 14-lead plastic so 0c to 70c supply voltage (v cc ) ................................................18v receiver enable input voltage ...................... C0.3v to 6v driver enable input voltage .......................... C0.3v to 6v driver input voltage ................................... C0.3v to 18v receiver input voltage ................................ C60v to 60v driver output voltage .................................. C60v to 60v receiver output voltage ................... C0.3v to (v cc + 6v) operating temperature range lt1785c/lt1791c/ lt1785ac/lt1791ac .................................... 0c to 70c lt1785i/lt1791i/ lt1785ai/lt1791ai .................................. C40c to 85c lt1785h/lt1791h/ lt1785ah/lt1791ah ............................. C40c to 125c storage temperature range ................... C65c to 150c lead temperature (soldering, 10 sec) .................. 300c
lt1785/lt1785a/ lt1791/lt1791a 3 178591fc lead free finish tape and reel part marking* package description temperature range lt1791in#pbf lt1791in#trpbf 1791i 14-lead pdip C40c to 85c lt1791is#pbf lt1791is#trpbf 1791i 14-lead plastic so C40c to 85c lt1791acn#pbf lt1791acn#trpbf 1791a 14-lead pdip 0c to 70c lt1791acs#pbf lt1791acs#trpbf 1791a 14-lead plastic so 0c to 70c lt1791ain#pbf lt1791ain#trpbf 1791ai 14-lead pdip C40c to 85c lt1791ais#pbf lt1791ais#trpbf 1791ai 14-lead plastic so C40c to 85c lt1791hn#pbf lt1791hn#trpbf 1791h 14-lead pdip C40c to 125c lt1791hs#pbf lt1791hs#trpbf 1791h 14-lead plastic so C40c to 125c lt1791ahn#pbf lt1791ahn#trpbf 1791ah 14-lead pdip C40c to 125c lt1791ahs#pbf lt1791ahs#trpbf 1791ah 14-lead plastic so C40c to 125c lead based finish tape and reel part marking* package description temperature range lt1785cn8 lt1785cn8#tr 1785 8-lead pdip 0c to 70c lt1785cs8 lt1785cs8#tr 1785 8-lead plastic so 0c to 70c lt1785in8 lt1785in8#tr 1785i 8-lead pdip C40c to 85c lt1785is8 lt1785is8#tr 1785i 8-lead plastic so C40c to 85c lt1785acn8 lt1785acn8#tr 1785a 8-lead pdip 0c to 70c lt1785acs8 lt1785acs8#tr 1785a 8-lead plastic so 0c to 70c lt1785ain8 lt1785ain8#tr 1785ai 8-lead pdip C40c to 85c lt1785ais8 lt1785ais8#tr 1785ai 8-lead plastic so C40c to 85c lt1785hn8 lt1785hn8#tr 1785h 8-lead pdip C40c to 125c lt1785hs8 lt1785hs8#tr 1785h 8-lead plastic so C40c to 125c lt1785ahn8 lt1785ahn8#tr 1785ah 8-lead pdip C40c to 125c lt1785ahs8 lt1785ahs8#tr 1785ah 8-lead plastic so C40c to 125c lt1791cn lt1791cn#tr 1791 14-lead pdip 0c to 70c lt1791cs lt1791cs#tr 1791 14-lead plastic so 0c to 70c lt1791in lt1791in#tr 1791i 14-lead pdip C40c to 85c lt1791is lt1791is#tr 1791i 14-lead plastic so C40c to 85c lt1791acn lt1791acn#tr 1791a 14-lead pdip 0c to 70c lt1791acs lt1791acs#tr 1791a 14-lead plastic so 0c to 70c lt1791ain lt1791ain#tr 1791ai 14-lead pdip C40c to 85c lt1791ais lt1791ais#tr 1791ai 14-lead plastic so C40c to 85c lt1791hn lt1791hn#tr 1791h 14-lead pdip C40c to 125c lt1791hs lt1791hs#tr 1791h 14-lead plastic so C40c to 125c lt1791ahn lt1791ahn#tr 1791ah 14-lead pdip C40c to 125c lt1791ahs lt1791ahs#tr 1791ah 14-lead plastic so C40c to 125c consult ltc marketing for parts speci? ed with wider operating temperature ranges. *the temperature grade is identi? ed by a label on the shipping container. for more information on lead free part marking, go to: http://www.linear.com/leadfree/ this product is only offered in trays. for more information go to: http://www.linear.com/packaging/ order information
lt1785/lt1785a/ lt1791/lt1791a 4 178591fc dc electrical characteristics the l denotes the speci? cations which apply over the full operating temperature range, otherwise speci? cations are at t a = 25c, v cc = 5v. symbol parameter conditions min typ max units v od1 differential driver output voltage (unloaded) i o = 0 l 4.1 5 v v od2 differential driver output voltage (with load) r = 50 (rs422), figure 1 r = 27 (rs485), figure 1 r = 18 l l l 2.0 1.5 1.2 2.70 2.45 2.2 v v v v od change in magnitude of driver differential output voltage for complementary output states r = 27 or r = 50, figure 1 l 0.2 v v oc driver common mode output voltage r = 27 or r = 50, figure 1 l 2 2.5 3 v |v oc | change in magnitude of driver common mode output voltage for complementary output states r = 27 or r = 50, figure 1 l 0.2 v v ih input high voltage di, de, re l 2v v il input low voltage di, de, re l 0.8 v i in1 input current di, de, re l 5a i in2 input current (a, b); (lt1791 or lt1785 with de = 0v) v in = 12v v in = C7v C60v v in 60v l l l C0.15 C6 0.15 C0.08 0.3 6 ma ma ma v th differential input threshold voltage for receiver lt1785/lt1791: C7v v cm 12v lt1785a/lt1791a: C7v v cm 12v l l C0.2 C0.2 0.2 0 v v v th receiver input hysteresis C7v < v cm < 12v 20 mv v oh receiver output high voltage i o = C400a, v id = 200mv l 3.5 4 v v ol receiver output low voltage i o = 1.6ma, v id = C200mv l 0.3 0.5 v three-state (high impedance) output current at receiver 0v < v out < 6v re > 2v or power off l C1 1 a r in receiver input resistance (lt1791) C7v v cm 12v C 60v v cm 60v l 85 125 125 k k lt1785 C7v v cm 12v l 50 90 k rs485 unit load 0.25 i sc driver short-circuit current v out = high, force v o = C7v v out = low, force v o = 12v l l 35 35 250 250 ma ma driver output fault current v o = 60v v o = C60v l l C6 6ma ma receiver short-circuit current 0v v o v cc l 35 ma driver three-state output current C7v v o 12v C60v v o 60v l l C0.2 C6 0.3 6 ma ma i cc supply current no load, re = 0v, de = 5v no load, re = 5v, de = 5v no load, re = 0v, de = 0v no load, re = 5v, de = 0v l l l l 5.5 5.5 4.5 0.2 9 9 8 0.3 ma ma ma ma
lt1785/lt1785a/ lt1791/lt1791a 5 178591fc switching characteristics the l denotes the speci? cations which apply over the full operating temperature range, otherwise speci? cations are at t a = 25c, v cc = 5v. symbol parameter conditions min typ max units t plh driver input to output figures 3, 5 l 700 2000 ns t phl driver input to output figures 3, 5 l 700 2000 ns t skew driver output to output figures 3, 5 100 ns t r , t f driver rise or fall time figures 3, 5 l 200 800 2000 ns t zh driver enable to output high figures 4, 6 l 500 3000 ns t zl driver enable to output low figures 4, 6 l 800 3000 ns t lz driver disable time from low figures 4, 6 l 200 5000 ns t hz driver disable time from high figures 4, 6 l 800 5000 ns t plh receiver input to output figures 3, 7 l 400 900 ns t phl receiver input to output figures 3, 7 l 400 900 ns t skd differential receiver skew 200 ns t zl receiver enable to output low figures 2, 8 l 300 1000 ns t zh receiver enable to output high figures 2, 8 l 300 1000 ns t lz receiver disable from low figures 2, 8 l 400 1000 ns t hz receiver disable from high figures 2, 8 l 400 1000 ns f max maximum data rate l 250 kbps t shdn time to shut down figures 2, 6, 8 3 s t zh(shdn) driver enable from shutdown to output high figures 2, 6; re = 5v 12 s t zl(shdn) driver enable from shutdown to output low figures 2, 6; re = 5v 12 s t zh(shdn) receiver enable from shutdown to output high figures 2, 8; de = 0v 4 s t zl(shdn) receiver enable from shutdown to output low figures 2, 8; de = 0v 4 s note 1: stresses beyond those listed under absolute maximum ratings may cause permanent damage to the device. exposure to any absolute maximum rating condition for extended periods may affect device reliability and lifetime.
lt1785/lt1785a/ lt1791/lt1791a 6 178591fc typical performance characteristics lt1785 input characteristics pins a or b; de = re = 0v supply current vs temperature receiver propagation delay vs differential input voltage driver differential output voltage vs load resistance driver differential output voltage vs temperature receiver propagation delay vs temperature driver propagation delay vs temperature lt1791 driver output leakage de = 0v lt1791 receiver input current vs v in load resistance () 10 output voltage (v) 4 3 2 1 0 100 1k 178591 g01 t a = 25c temperature (c) C40 differential voltage (v) 3.0 2.5 2.0 1.5 1.0 0.5 0 0 40 60 178591 g02 C20 20 80 100 r = 27 temperature (c) C40 delay (ns) 1000 800 600 400 200 0 0 40 60 178591 g03 C20 20 80 100 t plh t phl temperature (c) C40 propagation delay (ns) 1000 900 800 700 600 500 400 300 200 100 0 0 40 60 178591 g04 C20 20 80 100 hl lh 1ma/div 178591 g05 C60v v in 60v 200a/div 178591 g06 C60v v in 60v 1ma/div 178591 g07 C60v v a , v b 60v temperature (c) C40 i cc (ma) 7 6 5 4 3 2 1 0 0 40 60 178591 g08 C20 20 80 100 receiver only standby driver and receiver on v in differential (v) 0 delay (ns) 700 600 500 400 300 200 100 0 178591 g09 2 5 1 34 hl v cm = 12v hl v cm = C7v lh v cm = C7v lh v cm = 12v
lt1785/lt1785a/ lt1791/lt1791a 7 178591fc pin functions ro: receiver output. ttl level logic output. if the receiver is active ( re pin low), ro is high if receiver input a b by 200mv. if a b by 200mv, then ro will be low. ro assumes a high impedance output state when re is high or the part is powered off. ro is protected from output shorts from ground to 6v. re : receiver output enable. ttl level logic input. a logic low on re enables normal operation of the receiver output ro. a logic high level at re places the receiver output pin ro into a high impedance state. if receiver enable re and driver enable de are both in the disable state, the circuit- goes to a low power shutdown state. placing either re or de into its active state brings the circuit out of shutdown. shutdown state is not entered until a 3s delay after both re and de are disabled, allowing for logic skews in tog- gling between transmit and receive modes of operation. for can bus applications, re should be tied low to prevent the circuit from entering shutdown. de: driver output enable. ttl level logic input. a logic high on de enables normal operation of the driver out- puts (y and z on lt1791, a and b on lt1785). a logic low level at de places the driver output pins into a high impedance state. if receiver enable re and driver enable de are both in the disable state, the circuit goes to a low power shutdown state. placing either re or de into its active state brings the circuit out of shutdown. shutdown state is not entered until a 3s delay after both re and de are disabled, allowing for logic skews in toggling between transmit and receive modes of operation. for can bus operation the de pin is used for signal input to place the data bus in dominant or recessive states. di: driver input. ttl level logic input. a logic high at di causes driver output a or y to a high state, and output b or z to a low state. complementary output states occur for di low. for can bus applications di should be tied low. gnd: ground. y: driver output. the y driver output is in phase with the driver input di. in the lt1785 driver output y is internally connected to receiver input a. the driver output assumes a high impedance state when de is low, power is off or thermal shutdown is activated. the driver output is pro- tected from shorts between 60v in both active and high impedance modes. for can applications, output y is the canl output node. z: driver output. the z driver output is opposite in phase to the driver input di. in the lt1785 driver output z is internally connected to receiver input b. the driver output assumes a high impedance state when de is low, power is off or thermal shutdown is activated. the driver output is protected from shorts between 60v in both active and high impedance modes. for can applications, output z is the canh output node. a: receiver input. the a receiver input forces a high receiver output when v(a) [v(b) + 200mv]. v(a) [v(b)C 200mv] forces a receiver output low. receiver inputs a and b are protected against voltage faults between 60v. the high input impedance allows up to 128 lt1785 or lt1791 transceivers on one rs485 data bus. the lt1785a/lt1791a have guaranteed receiver input thresholds C200mv < v th < 0. receiver outputs are guaranteed to be in a high state for 0v inputs. b: receiver input. the b receiver input forces a high receiver output when v(a) [v(b) + 200mv]. when v(a) [v(b) C 200mv], the b receiver forces a receiver output low. receiver inputs a and b are protected against voltage faults between 60v. the high input impedance allows up to 128 lt1785 or lt1791 transceivers on one rs485 data bus. the lt1785a/lt1791a have guaranteed receiver input- thresholds C200mv < v th < 0. receiver outputs are guaranteed to be in a high state for 0v inputs. v cc : positive supply input. for rs422 or rs485 operation, 4.75v v cc 5.25v. higher v cc input voltages increase output drive swing. v cc should be decoupled with a 0.1f low esr capacitor directly at pin 8 (v cc ).
lt1785/lt1785a/ lt1791/lt1791a 8 178591fc test circuits figure 1. driver dc test load figure 2. receiver timing test load figure 3. driver/receiver timing test circuit figure 4. driver timing test load v od a b r r v oc 1785/91 f01 receiver output c rl 1k s1 s2 test point v cc 1k 1785/91 f02 5v de a b di r diff c l1 c l2 ro 15pf a b re 1785/91 f03 output under test c l s1 s2 v cc 500 1785/91 f04 lt1785 transmitting inputs outputs re de di a b ro 0100 1 0 0111 0 1 1 0 x hi-z hi-z hi-z 1 1 0 0 1 hi-z 1 1 1 1 0 hi-z lt1785 receiving inputs output re de di a-b ro 0 0 x C200mv 0 0 0 x 200mv* 1 0 0 x open 1 1 0 x x hi-z * 0mv for lt1785a lt1791 inputs outputs re de di a-b y z ro 0 0 x C200mv hi-z hi-z 0 0 0 x 200mv* hi-z hi-z 1 0 0 x open hi-z hi-z 1 0 1 0 C200mv 0 1 0 0 1 0 200mv* 0 1 1 0 1 0 open 0 1 1 0 1 1 C200mv 1 0 0 0 1 1 200mv* 1 0 1 0 1 1 open 1 0 1 1 0 x x hi-z hi-z hi-z 1 1 0 x 0 1 hi-z 1 1 1 x 1 0 hi-z * 0mv for lt1791a function tables
lt1785/lt1785a/ lt1791/lt1791a 9 178591fc switching time waveforms figure 5. driver propagation delays di 5v 1.5v t plh t r t skew 1/2 v o v o f = 125khz, t r 10ns, t f 10ns 90% 10% 0v b a v o Cv o 0v 90% 1.5v t phl t skew 1/2 v o 10% t f v diff = v(a) C v(b) 1785/91 f05 figure 6. driver enable and disable times 1.5v 2.3v 2.3v t zh(shdn) ,t zh t zl(shdn) ,t zl 1.5v t lz 0.5v 0.5v t hz output normally low output normally high 5v 0v de 5v v ol v oh 0v a, b a, b 178591 f06 f = 125khz, t r 10ns, t f 10ns figure 7. receiver propagation delays 1.5v t phl ro Cv od2 a C b 0v 0v 1.5v t plh output input v od2 v ol v oh 178591 f07 f = 125khz, t r 10ns, t f 10ns figure 8. receiver enable and disable times 1.5v t zl(shdn) , t zl t zh(shdn) , t zh 1.5v 1.5v 1.5v t lz 0.5v 0.5v t hz output normally low output normally high 5v 0v re 5v 0v ro ro 178591 f08 f = 125khz, t r 10ns, t f 10ns
lt1785/lt1785a/ lt1791/lt1791a 10 178591fc applications information overvoltage protection the lt1785/lt1791 rs485/rs422 transceivers answer an applications need for overvoltage fault tolerance on data networks. industrial installations may encounter common mode voltages between nodes far greater than the C7v to 12v range speci? ed for compliance to rs485 standards. cmos rs485 transceivers can be damaged by voltages above their absolute maximum ratings of typically C8v to 12.5v. replacement of standard rs485 transceiver components with the lt1785 or lt1791 devices eliminates ? eld failures due to overvoltage faults or the use of costly external protection devices. the limited overvoltage toler- ance of cmos rs485 transceivers makes implementation of effective external protection networks dif? cult without interfering with proper data network performance within the C7v to 12v region of rs485 operation. the high overvoltage rating of the lt1785/lt1791 facili- tates easy extension to almost any level. simple discrete component networks that limit the receiver input and driver output voltages to less than 60v can be added to the device to extend protection to any desired level. figure 11 shows a protection network against faults to the120vac line voltage. the lt1785/lt1791 protection is achieved by using a high voltage bipolar integrated circuit process for the transceiv- ers. the naturally high breakdown voltages of the bipolar process provides protection in powered-off and high impedance conditions. the driver outputs use a foldback current limit design to protect against overvoltage faults while still allowing high current output drive. esd protection the lt1785/lt1791 i/o pins have on-chip esd protection circuitry to eliminate ? eld failures caused by discharges to exposed ports and cables in application environments. the lt1785 pins a and b and the lt1791 driver output pins y and z are protected to iec-1000-4-2 level 2. these pins will survive multiple esd strikes of 15kv air discharge or 4kv contact discharge. due to their very high input impedance, the lt1791 receiver pins are protected to iec-1000-4-2 level 2, or 15kv air and 4kv contact discharges. this level of esd protection will guarantee immunity from ? eld failures in all but the most severe esd environments. the lt1791 receiver input esd tolerance may be increased to iec level 4 compliance by adding 2.2k resistors in series with these pins. low power shutdown the lt1785/lt1791 have re and de logic inputs to control the receive and transmit modes of the transceivers. the re input allows normal data reception when in the low state. the receiver output goes to a high impedance state when re is high, allowing multiplexing the ro data line. the de logic input performs a similar function on the driver outputs. a high state on de activates the differential driver outputs, a low state places both driver outputs in to high impedance. tying the re and de logic inputs together may be done to allow one logic signal to toggle the transceiver from receive to transmit modes. the de input is used as the data input in can bus applications. disabling both the driver and receiver places the device into a low supply current shutdown mode. an internal time delay of 3s minimum prevents entering shutdown due to small logic skews when a toggle between receive and transmit is desired. the recovery time from shutdown mode is typically 12s. the user must be careful to allow for this wake-up delay from shutdown mode. to allow full 250kbaud data rate transmission in can applications, the re pin should be tied low to prevent entering shutdown mode.
lt1785/lt1785a/ lt1791/lt1791a 11 178591fc applications information slew limiting for emi emissions control the lt1785/lt1791 feature controlled driver output slew rates to control high frequency emi emissions from equip- ment and data cables. the slew limiting limits data rate operation to 250kbaud. slew limiting also mitigates the adverse affects of imperfect transmission line termina- tion caused by stubs or mismatched cable. in some low speed, short distance networks, cable termination may be eliminated completely with no adverse effect on data transmission. data network cable selection and termination long distance data networks operating at high data trans- mission rates should use high quality, low attenuation cable with well-matched cable terminations. short distance networks at low data rates may use much less expensive pvc cable. these cables have characteristic impedances as low as 72. the lt1785/lt1791 output drivers are guaranteed to drive cables as low as 72. figure 9. full-duplex rs422 5 4 3 2 a b z y 12 11 10 9 ro re de di 178591 f09 tx 120 5 4 3 2 y z b a 9 10 11 12 ro lt1791 lt1791 re de di rx tx 120 rx
lt1785/lt1785a/ lt1791/lt1791a 12 178591fc package description n8 package 8-lead pdip (narrow 0.300) (ltc dwg # 05-08-1510) n8 1002 .065 (1.651) typ .045 ?.065 (1.143 ?1.651) .130 .005 (3.302 0.127) .020 (0.508) min .018 .003 (0.457 0.076) .120 (3.048) min 12 3 4 87 6 5 .255 .015* (6.477 0.381) .400* (10.160) max .008 ?.015 (0.203 ?0.381) .300 ?.325 (7.620 ?8.255) .325 +.035 ?015 +0.889 0.381 8.255 () note: 1. dimensions are inches millimeters *these dimensions do not include mold flash or protrusions. mold flash or protrusions shall not exceed .010 inch (0.254mm) .100 (2.54) bsc
lt1785/lt1785a/ lt1791/lt1791a 13 178591fc package description s8 package 8-lead plastic small outline (narrow 0.150) (ltc dwg # 05-08-1610) .016 ?.050 (0.406 ?1.270) .010 ?.020 (0.254 ?0.508) 45 0 ?8 typ .008 ?.010 (0.203 ?0.254) so8 0303 .053 ?.069 (1.346 ?1.752) .014 ?.019 (0.355 ?0.483) typ .004 ?.010 (0.101 ?0.254) .050 (1.270) bsc 1 2 3 4 .150 ?.157 (3.810 ?3.988) note 3 8 7 6 5 .189 ?.197 (4.801 ?5.004) note 3 .228 ?.244 (5.791 ?6.197) .245 min .160 .005 recommended solder pad layout .045 .005 .050 bsc .030 .005 typ inches (millimeters) note: 1. dimensions in 2. drawing not to scale 3. these dimensions do not include mold flash or protrusions. mold flash or protrusions shall not exceed .006" (0.15mm)
lt1785/lt1785a/ lt1791/lt1791a 14 178591fc package description n package 14-lead pdip (narrow 0.300) (ltc dwg # 05-08-1510) n14 1103 .020 (0.508) min .120 (3.048) min .130 .005 (3.302 0.127) .045 ?.065 (1.143 ?1.651) .065 (1.651) typ .018 .003 (0.457 0.076) .005 (0.127) min .255 .015* (6.477 0.381) .770* (19.558) max 3 1 2 4 5 6 7 8 9 10 11 12 13 14 .008 ?.015 (0.203 ?0.381) .300 ?.325 (7.620 ?8.255) .325 +.035 ?015 +0.889 0.381 8.255 () note: 1. dimensions are inches millimeters *these dimensions do not include mold flash or protrusions. mold flash or protrusions shall not exceed .010 inch (0.254mm) .100 (2.54) bsc
lt1785/lt1785a/ lt1791/lt1791a 15 178591fc 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 representa- tion that the interconnection of its circuits as described herein will not infringe on existing patent rights. package description s package 14-lead plastic small outline (narrow 0.150) (ltc dwg # 05-08-1610) 1 n 2 3 4 .150 ?.157 (3.810 ?3.988) note 3 14 13 .337 ?.344 (8.560 ?8.738) note 3 .228 ?.244 (5.791 ?6.197) 12 11 10 9 5 6 7 n/2 8 .016 ?.050 (0.406 ?1.270) .010 ?.020 (0.254 ?0.508) 45 0 ?8 typ .008 ?.010 (0.203 ?0.254) s14 0502 .053 ?.069 (1.346 ?1.752) .014 ?.019 (0.355 ?0.483) typ .004 ?.010 (0.101 ?0.254) .050 (1.270) bsc .245 min n 1 2 3 n/2 .160 .005 recommended solder pad layout .045 .005 .050 bsc .030 .005 typ inches (millimeters) note: 1. dimensions in 2. drawing not to scale 3. these dimensions do not include mold flash or protrusions. mold flash or protrusions shall not exceed .006" (0.15mm)
lt1785/lt1785a/ lt1791/lt1791a 16 178591fc linear technology corporation 1630 mccarthy blvd., milpitas, ca 95035-7417 (408) 432-1900 fax: (408) 434-0507 www.linear.com ? linear technology corporation 1998 lt 0409 rev c ? printed in usa related parts typical application part number description comments ltc485 low power rs485 interface transceiver i cc = 300a (typ) ltc491 differential driver and receiver pair i cc = 300a ltc1483 ultralow power rs485 low emi transceiver controlled driver slew rate ltc1485 differential bus transceiver 10mbaud operation ltc1487 ultralow power rs485 with low emi, shutdown and high input impedance up to 256 transceivers on the bus ltc1520 50mbps precision quad line receiver channel-to-channel skew 400ps (typ) ltc1535 isolated rs485 full-duplex transceiver 2500v rms isolation in surface mount package ltc1685 52mbps rs485 half-duplex transceiver propagation delay skew 500ps (typ) ltc1687 52mbps rs485 full-duplex transceiver propagation delay skew 500ps (typ) figure 10. half-duplex rs485 network operation 4 3 2 1 a b 7 6 ro re de di 178591 f10 rx tx r t 120 r t 120 lt1785 4 3 2 1 a b 7 6 ro re de di rx tx lt1785 4 3 2 1 a b 7 6 ro re de di 4 3 2 1 a b 7 6 ro re de di lt1785 lt1785 4 3 2 1 a b 7 8 v cc 5 6 ro re de di rx tx r t ,120 178591 f11 0.1f 300v 47 1.5ke36ca 47 carbon composite 5w lt1785 raychem polyswitch tr600-150 2 figure 11. rs485 network with 120v ac line fault protection

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