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general description the max3293/max3294/max3295 low-power, high- speed transmitters for rs-485/rs-422 communication operate from a single +3.3v power supply. these devices contain one differential transmitter. the max3295 transmitter operates at data rates up to 20mbps, with an output skew of less than 5ns, and a guaranteed driver propagation delay below 25ns. the max3293 (250kbps) and max3294 (2.5mbps) are slew-rate limited to minimize emi and reduce reflections caused by improperly terminated cables. the max3293/max3294/max3295 output level is guar- anteed at +1.5v with a standard 54 load, compliant with rs-485 specifications. the transmitter draws 5ma of supply current when unloaded, and 1? in low- power shutdown mode (de = gnd). hot-swap circuitry eliminates false transitions on the data cable during circuit initialization or connection to a live backplane, and short-circuit current limiting and thermal- shutdown circuitry protect the driver against excessive power dissipation. the max3293/max3294/max3295 are offered in a 6-pin sot23 package, and are specified over the automotive temperature range. applications rs-485/rs-422 communications clock distribution telecom equipment automotive security equipment point-of-sale equipment industrial control features ? space-saving 6-pin sot23 package ? 250kbps/2.5mbps/20mbps data rates available ? operate from a single +3.3v supply ? esd protection 9kvhuman body model ? slew-rate limited for errorless data transmission (max3293/max3294) ? 1 a low-current shutdown mode ? -7v to +12v common-mode input voltage range ? current limiting and thermal shutdown for driver-overload protection ? hot-swap inputs for telecom applications ? automotive temperature range (-40c to +125c) max3293/max3294/max3295 20mbps, +3.3v, sot23 rs-485/ rs-422 transmitters ________________________________________________________________ maxim integrated products 1 selector guide ordering information 19-2770; rev 3; 3/11 for pricing, delivery, and ordering information, please contact maxim direct at 1-888-629-4642, or visit maxim? website at www.maxim-ic.com. part temp range pin-package max3293 aut+t -40c to +125c 6 sot23-6 max3294 aut+t -40c to +125c 6 sot23-6 max3295 aut+t -40c to +125c 6 sot23-6 part maximum data rate (mbps) slew- rate limited top mark max3293aut+t 0.25 yes abni or abvh max3294aut+t 2.5 yes abnj or abvi MAX3295AUT+t 20 no abnk or abvj typical operating circuit max3293 max3294 max3295 d di de max3280e max3281e max3283e max3284e r ro 120 z y + denotes a lead(pb)-free/rohs-compliant package. t = tape and reel. pin configuration appears at end of data sheet.
max3293/max3294/max3295 20mbps, +3.3v, sot23 rs-485/ rs-422 transmitters 2 _______________________________________________________________________________________ absolute maximum ratings electrical characteristics (v cc = +3.3v ?%, t a = t min to t max , unless otherwise noted. typical values are at v cc = +3.3v and t a = +25?.) (notes 1, 2) stresses beyond those listed under ?bsolute maximum ratings?may cause permanent damage to the device. these are stress rating s only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specificatio ns is not implied. exposure to absolute maximum rating conditions for extended periods may affect device reliability. (all voltages referenced to gnd, unless otherwise noted.) supply voltage (v cc ).............................................................+6v de, di .......................................................................-0.3v to +6v y, z .........................................................................-7v to +12.5v maximum continuous power dissipation (t a = +70?) sot23 (derate 8.2mw/? above +70?) .................654.1mw operating temperature ranges max32_ _aut...............................................-40? to +125? storage temperature range .............................-65? to +160? junction temperature .....................................................+160? lead temperature (soldering, 10s) .................................+300? soldering temperature (reflow) .......................................+260? parameter symbol conditions min typ max units power supply supply voltage v cc 3.135 3.300 3.465 v supply current in normal operation i q no load, di = v cc or gnd, de = v cc 5ma supply current in shutdown mode i shdn no load, de = gnd 1 10 a driver r = 50 (rs-422), t a +85? 2.0 v cc differential driver output v od figure 1, de = v cc , di = gnd or v cc r = 27 (rs-485), t a +85? 1.5 v cc v change in magnitude of differential output voltage v od figure 1, r = 27 or 50 , de = v cc (note 3) 0.2 v driver common-mode output voltage v oc figure 1, r = 27 or 50 , de = v cc , di = v cc or gnd -1 +3 v change in magnitude of common- mode voltage v oc figure 1, r = 27 or 50 (note 3) 0.2 v driver logic input high voltage v ih de, di 2.0 v input low voltage v il de, di 0.8 v input current i in de, di -2 +2 ? v in = +12v -20 +20 output leakage i o y, z de = gnd, v cc = gnd or +3.3v v in = -7v -20 +20 ? (v cc - 1v) v out +12v, output high +25 driver short-circuit foldback output current i osfd -7v v out 1v, output high -25 ma 0 v out +12v, output low -250 driver short-circuit output current i osd -7v v out v cc , output high +250 ma thermal-shutdown threshold t ts 160 ? thermal-shutdown hysteresis t tsh 40 ? esd protection y, z human body model ? kv
max3293/max3294/max3295 20mbps, +3.3v, sot23 rs-485/ rs-422 transmitters _______________________________________________________________________________________ 3 switching characteristics (max3293) (v cc = +3.3v ?%, t a = +25?, unless otherwise noted. typical values are at v cc = +3.3v.) switching characteristics (max3294) (v cc = +3.3v ?%, t a = +25?, unless otherwise noted. typical values are at v cc = +3.3v.) parameter symbol conditions min typ max units t plh 400 1300 driver propagation delay t phl figures 2, 3; r diff = 54 , c l = 50pf 400 1300 ns t r 400 1200 driver differential output rise or fall time t f figures 2, 3; r diff = 54 , c l = 50pf 400 1200 ns driver-output skew t skew figures 2, 3; r diff = 54 , c l = 50pf, t skew = | t plh - t phl | (note 5) -400 +400 ns differential driver-output skew t dskew figures 2, 3; r diff = 54 , c l = 50pf -100 +100 ns maximum data rate figures 2, 3; r diff = 54 , c l = 50pf 250 kbps driver enable to output high t zh figures 4, 5; s2 closed, r l = 500 , c l = 100pf 2000 ns driver enable to output low t zl figures 4, 5; s1 closed, r l = 500 , c l = 100pf 2000 ns driver disable time from low t lz figures 4, 5; s1 closed, r l = 500 , c l = 100pf 1000 ns driver disable time from high t hz figures 4, 5; s2 closed, r l = 500 , c l = 100pf 1000 ns device-to-device propagation delay matching same power supply, maximum temperature difference between devices = +30c (note 5) 900 ns parameter symbol conditions min typ max units t plh 24 70 driver propagation delay t phl figures 2, 3; r diff = 54 , c l = 50pf 24 70 ns t r 10 70 driver differential output rise or fall time t f figures 2, 3; r diff = 54 , c l = 50pf 10 70 ns driver-output skew t skew figures 2, 3; r diff = 54 , c l = 50pf, t skew = | t plh - t phl | (note 5) -40 +40 ns differential driver-output skew t dskew figures 2, 3; r diff = 54 , c l = 50pf -6 +6 ns maximum data rate figures 2, 3; r diff = 54 , c l = 50pf 2.5 mbps driver enable to output high t zh figures 4, 5; s2 closed, r l = 500 , c l = 100pf 400 ns driver enable to output low t zl figures 4, 5; s1 closed, r l = 500 , c l = 100pf 400 ns driver disable time from low t lz figures 4, 5; s1 closed, r l = 500 , c l = 100pf 100 ns driver disable time from high t hz figures 4, 5; s2 closed, r l = 500 , c l = 100pf 100 ns device-to-device propagation delay matching same power supply, maximum temperature difference between devices = +30c (note 5) 46 ns
max3293/max3294/max3295 20mbps, +3.3v, sot23 rs-485/ rs-422 transmitters 4 _______________________________________________________________________________________ note 1: devices production tested at +25?. limits over the operating temperature range are guaranteed by design. note 2: all currents into the device are positive; all currents out of the device are negative. all voltages are referenced to device ground, unless otherwise noted. note 3: v od and v oc are the changes in v od and v oc , respectively, when the di input changes state. note 4: the maximum current applies to peak current just prior to foldback current limiting. note 5: guaranteed by design; not production tested. switching characteristics (max3295) (v cc = +3.3v ?%, t a = +25?, unless otherwise noted. typical values are at v cc = +3.3v.) parameter symbol conditions min typ max units t plh 25 driver propagation delay t phl figures 2, 3; r diff = 54 , c l = 50pf 25 ns t a = -40c to +125c 18.5 t r t a < +85c 15 t a = -40c to +125c 18.5 driver differential output rise or fall time t f figures 2, 3; r diff = 54 , c l = 50pf t a < +85c 15 ns driver-output skew t skew figures 2, 3; r diff = 54 , c l = 50pf, t skew = | t plh - t phl | 5 ns differential driver-output skew t dskew figures 2, 3; r diff = 54 , c l = 50pf 5 ns figures 2, 3; r diff = 54 , c l = 50pf, t a +85c 20 maximum data rate figures 2, 3; r diff = 54 , c l = 50pf 16 mbps driver enable to output high t zh figures 4, 5; s2 closed, r l = 500 , c l = 100pf 400 ns driver enable to output low t zl figures 4, 5; s1 closed, r l = 500 , c l = 100pf 400 ns driver disable time from low t lz figures 4, 5; s1 closed, r l = 500 , c l = 100pf 100 ns driver disable time from high t hz figures 4, 5; s2 closed, r l = 500 , c l = 100pf 100 ns device-to-device propagation delay matching same power supply, maximum temperature difference between devices = +30c (note 5) 25 ns
max3293/max3294/max3295 20mbps, +3.3v, sot23 rs-485/ rs-422 transmitters _______________________________________________________________________________________ 5 y z v od r r v oc di de 3v y v id c l c l r diff z di 3v 0v z y v o 0v -v o v o 1.5v 1/2 v o 1/2 v o t plh t f t r t phl 10% 90% 90% 1.5v 10% v diff = v (y) - v (z) t skew = | t plh - t phl | v diff f = 1mhz, t r 3ns, t f 3ns s1 s2 output under test v cc c l r l figure 1. driver dc test load figure 2. driver timing test circuit figure 3. driver propagation delays figure 4. enable/disable timing test load output normally low output normally high 3v 0v y, z v ol y, z 0v 1.5v 1.5v v ol + 0.25v v oh - 0.25v 2.3v 2.3v t zl(shdn) , t zl t lz t zh(shdn) , t zh t hz de figure 5. driver enable and disable times test circuits and timing diagrams
0 10 20 30 40 max3293-95 toc09 temperature ( c) propagation delay (ns) -40 20 50 80 -10 110 driver propagation delay vs. temperature t phl t plh r diff = 54 c l = 50pf 0 1 2 3 4 output skew vs. temperature max3293-95 toc08 temperature ( c) output skew (ns) -40 20 50 80 -10 110 driver-output current vs. driver-output high voltage max3293-95 toc07 output high voltage (v) output current (ma) 0 -100 -40 -60 -80 -20 -120 -7 -5 -3 -1 1 3 5 20 0 10 30 20 40 50 output current vs. differential output voltage max3293-95 toc04 differential output voltage (v) output current (ma) 1.75 2.75 2.25 2.50 2.00 3.00 3.25 3.50 1.0 2.0 2.5 3.0 3.5 max3293-95 toc05 temperature ( c) differential output voltage (v) -40 20 50 80 -10 110 driver differential output voltage vs. temperature r diff = 54 r diff = 100 1.5 driver-output current vs. driver-output low voltage max3293-95 toc06 output low voltage (v) output current (ma) 20 80 60 40 100 0 024681012 140 120 0 5 10 20 15 25 max3295 supply current vs. data rate max3293-95 toc01 data rate (mbps) supply current (ma) 010 51520 de = v cc no load t a = +85 c t a = +125 c t a = +25 c t a = -40 c 0 0.5 1.0 1.5 2.0 supply current vs. temperature max3293-95 toc02 temperature ( c) supply current (ma) -40 20 50 80 -10 110 de = v cc no load no switching 0 1.6 1.2 0.8 0.4 2.0 max3293-95 toc03 temperature ( c) supply current ( a) -40 20 50 80 -10 110 shutdown supply current vs. temperature de = gnd max3293/max3294/max3295 20mbps, +3.3v, sot23 rs-485/ rs-422 transmitters 6 _______________________________________________________________________________________ typical operating characteristics (v cc = +3.3v, t a = +25?, unless otherwise noted.)
driver propagation delay max3293-95 toc10 20ns/div y, z: 1v/div di: 2v/div di 0v 0v y, z typical operating characteristics (continued) (v cc = +3.3v, t a = +25?, unless otherwise noted.) max3293/max3294/max3295 20mbps, +3.3v, sot23 rs-485/ rs-422 transmitters _______________________________________________________________________________________ 7 enable response time max3293-95 toc11 40ns/div de 0v 0v y-z y, z, de: 2v/div unloaded driver-output waveform (f in = 16mbps) max3293-95 toc12 20ns/div y, z: 1v/div 0v y, z loaded driver-output waveform (f in = 16mbps) max3293-95 toc13 20ns/div y, z: 500mv/div 0v y, z eye diagram (f in = 20mbps) max3293-95 toc14 10ns/div y, z: 500mv/div 0v y, z pin description pin name function 1di driver input. a logic low on di forces the noninverting output (y) low and the inverting output (z) high. a logic high on di forces the noninverting output (y) high and the inverting output (z) low. 2v cc positive supply. v cc = +3.3v ?%. bypass v cc to gnd with a 0.1? capacitor. 3de driver output enable. force de high to enable driver. pull de low to disable the driver. hot-swap input, see the hot-swap capability section. 4 z inverting rs-485/rs-422 output 5 gnd ground 6 y noninverting rs-485/rs-422 output
max3293/max3294/max3295 20mbps, +3.3v, sot23 rs-485/ rs-422 transmitters 8 _______________________________________________________________________________________ detailed description the max3293/max3294/max3295 are low-power transmitters for rs-485/rs-422 communication. the max3295 operates at data rates up to 20mbps, the max3294 up to 2.5mbps (slew-rate limited), and the max3293 up to 250kbps (slew-rate limited). these devices are enabled using an active-high driver enable (de) input. when disabled, outputs enter a high-imped- ance state, and the supply current reduces to 1?. the max3293/max3294/max3295 have a hot-swap input structure that prevents disturbance on the differ- ential signal lines when a circuit board is plugged into a ?ot?backplane (see the hot-swap capability sec- tion). drivers are also short-circuit current limited and are protected against excessive power dissipation by thermal-shutdown circuitry. driver the driver accepts a single-ended, logic-level input (di) and translates it to a differential rs-485/rs-422 level output (y and z). driving de high enables the dri- ver, while pulling de low places the driver outputs (y and z) into a high-impedance state (see table 1). low-power shutdown force de low to disable the max3293/max3294/ max3295. in shutdown mode, the device consumes a maximum of 10? of supply current. hot-swap capability hot-swap input when circuit boards are inserted into a ?ot?or pow- ered backplane, disturbances to the enable can lead to data errors. upon initial circuit board insertion, the processor undergoes its power-up sequence. during this period, the output drivers are high impedance and are unable to drive the de input of the max3293/ max3294/max3295 to a defined logic level. leakage currents up to 10? from the high-impedance output could cause de to drift to an incorrect logic state. additionally, parasitic circuit board capacitance could cause coupling of v cc or gnd to de. these factors could improperly enable the driver. the max3293/max3294/max3295 eliminate all above issues with hot-swap circuitry. when v cc rises, an internal pulldown circuit holds de low for approximately 10?. after the initial power-up sequence, the pulldown circuit becomes transparent, resetting the hot-swap tol- erable input. table 1. max3293/max3294/ max3295 (rs-485/rs-422) transmitting function table x = don? care. inputs outputs de di y z 0 x shutdown shutdown 1001 1110 v cc timer timer en de (hot swap) 10 s 100 a m1 m2 5.6k 2ma figure 6. simplified structure of the driver enable input (de) figure 7. differential power-up glitch (0.1v/?) differential power-up glitch (0.1v/ s) 4 s/div 2v/div v cc y z y-z 0v 10mv/div ac-coupled 10mv/div ac-coupled 20mv/div
max3293/max3294/max3295 20mbps, +3.3v, sot23 rs-485/ rs-422 transmitters _______________________________________________________________________________________ 9 hot-swap input circuitry the max3293/max3294/max3295 enable input fea- tures hot-swap capability. at the input, there are two nmos devices, m1 and m2 (figure 6). when v cc ramps from zero, an internal 10? timer turns on m2 and sets the sr latch, which also turns on m1. transistors m2, a 2ma current sink, and m1, a 100? current sink, pull de to gnd through a 5.6k resistor. m2 is designed to pull de to the disabled state against an external parasitic capacitance up to 100pf that may drive de high. after 10?, the timer deactivates m2 while m1 remains on, holding de low against three- state leakages that can drive de high. m1 remains on until an external source overcomes the required input current. at this time, the sr latch resets and m1 turns off. when m1 turns off, de reverts to a standard, high- impedance cmos input. whenever v cc drops below 1v, the hot-swap input is reset. hot-swap line transient during a hot-swap event when the driver is connected to the line and is powered up, the driver must not cause the differential signal to drop below 200mv. figures 7, 8, and 9 show the results of the max3295 during power-up for three different v cc ramp rates (0.1v/?, 1v/?, and 10v/?). the photos show the v cc ramp, the single- ended signal on each side of the 100 termination, as well as the differential signal across the termination. esd protection human body model figure 10 shows the human body model, and figure 11 shows the current waveform it generates when dis- charged into low impedance. this model consists of a 100pf capacitor charged to the esd voltage of interest, which is then discharged into the device through a 1.5k resistor. figure 8. differential power-up glitch (1v/?) figure 9. differential power-up glitch (10v/?) figure 11. current waveform differential power-up glitch (10v/ s) 200ns/div 2v/div v cc y z y-z 0v 50mv/div ac-coupled 50mv/div ac-coupled 100mv/div differential power-up glitch (1v/ s) 1 s/div 2v/div v cc y z y-z 0v 100mv/div ac-coupled 100mv/div ac-coupled 200mv/div figure 10. human body esd test charge-current- limit resistor discharge resistance storage capacitor c s 100pf r c 1m r d 1.5k high- voltage dc source device under test i p 100% 90% 36.8% t rl time t dl current waveform peak-to-peak ringing (not drawn to scale) i r 10% 0v 0v amperes
reduced emi and reflections (max3293/max3294) the max3293/max3294 are slew-rate limited, minimiz- ing emi and reducing reflections caused by improperly terminated cables. figure 12 shows fourier analysis of the max3295 transmitting a 125khz signal. high-fre- quency harmonics with large amplitudes are evident. figure 13 shows the same information, but for the slew- rate-limited max3293, transmitting the same signal. the high-frequency harmonics have much lower ampli- tudes, and the potential for emi is significantly reduced. to minimize reflections, the line should be terminated at both ends in its characteristic impedance, and stub lengths off the main line should be kept as short as possible. the slew-rate-limited max3293 and max3294 are more tolerant of imperfect termination. driver-output protection two mechanisms prevent excessive output current and power dissipation caused by faults or by bus contention. the first, a foldback current limit on the output stage, provides immediate protection against short circuits over the whole common-mode voltage range (see the typical operating characteristics ). the second, a thermal-shut- down circuit, forces the driver outputs into a high-imped- ance state if the die temperature exceeds +160?. max3293/max3294/max3295 20mbps, +3.3v, sot23 rs-485/ rs-422 transmitters 10 ______________________________________________________________________________________ figure 12. driver-output waveform and fft plot of max3295 transmitting a 125khz signal figure 13. driver-output waveform and fft plot of max3293 transmitting a 125khz signal driver-output waveform and fft plot of max3293 10db/div chip information process: bicmos driver-output waveform and fft plot of max3295 10db/div v cc z de 16 y + 5 gnd di max3293 max3294 max3295 sot23-6 top view 2 34 pin configuration package information for the latest package outline information and land patterns (footprints), go to www.maxim-ic.com/packages . note that a ?? ?? or ??in the package code indicates rohs status only. package drawings may show a different suffix character, but the drawing pertains to the package regardless of rohs status. package type package code outline no. land pattern no. 6 sot23 u6cn+2 21-0058 90-0175
max3293/max3294/max3295 20mbps, +3.3v, sot23 rs-485/ rs-422 transmitters maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a maxim product. no circu it patent licenses are implied. maxim reserves the right to change the circuitry and specifications without notice at any time. maxim integrated products, 120 san gabriel drive, sunnyvale, ca 94086 408-737-7600 ____________________ 11 2011 maxim integrated products maxim is a registered trademark of maxim integrated products, inc. revision history revision number revision date description pages changed 3 3/11 added lead-free parts to the ordering information and selector guide tables 1

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