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general description the max13487e/max13488e +5v, half-duplex, ?5kv esd-protected rs-485/rs-422-compatible transceivers feature one driver and one receiver. the max13487e/ max13488e include a hot-swap capability to eliminate false transitions on the bus during power-up or live insertion. the max13487e/max13488e feature maxim? propri- etary autodirection control. this architecture makes the devices ideal for applications, such as isolated rs-485 ports, where the driver input is used in conjunction with the driver-enable signal to drive the differential bus. the max13487e features reduced slew-rate drivers that minimize emi and reduce reflections caused by improperly terminated cables, allowing error-free trans- mission up to 500kbps. the max13488e driver slew rate is not limited, allowing transmit speeds up to 16mbps. the max13487e/max13488e feature a 1/4-unit load receiver input impedance, allowing up to 128 trans- ceivers on the bus. these devices are intended for half- duplex communications. all driver outputs are protected to ?5kv esd using the human body model. the max13487e/max13488e are available in an 8-pin so package. the devices operate over the extended -40? to +85? temperature range. applications isolated rs-485 interfaces utility meters industrial controls industrial motor drives automated hvac systems features ? +5v operation ? autodirection enables driver automatically on transmission ? hot-swappable for telecom applications ? enhanced slew-rate limiting facilitates error- free data transmission (max13487e) ? high-speed version (max13488e) allows for transmission speeds up to 16mbps ? extended esd protection for rs-485 i/o pins 15kv human body model ? 1/4-unit load, allowing up to 128 transceivers on the bus ? 8-pin so package max13487e/max13488e half-duplex rs-485-/rs-422-compatible transceiver with autodirection control ________________________________________________________________ maxim integrated products 1 19-0740; rev 0; 1/07 for pricing, delivery, and ordering information, please contact maxim/dallas direct! at 1-888-629-4642, or visit maxim? website at www.maxim-ic.com. evaluation kit available ordering information/ selector guide part pin- package slew-rate limited pkg code max13487e esa+ 8 so yes s8-2 max13488e esa+ 8 so no s8-2 + denotes a lead-free package note: all devices operate over the -40? to +85? temperature range. pin configuration/typical application circuit appear at end of data sheet. v cc 8 - + + - state machine d r a b re di ro com de re gnd shdn 1 3 2 4 6 7 5 ri di v dt max13487e max13488e functional diagram
max13487e/max13488e half-duplex rs-485-/rs-422-compatible transceiver with autodirection control 2 _______________________________________________________________________________________ absolute maximum ratings 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.) supply voltage v cc ...............................................................+6v shdn , re , di..............................................................-0.3v to +6 a, b........................................................................... -8v to +13v short-circuit duration (ro, a, b) to gnd ..................continuous continuous power dissipation (t a = +70?) 8-pin so (derate 5.9mw/? above +70?)..................471mw operating temperature range ...........................-40? to +85? junction temperature ......................................................+150? storage temperature range .............................-65? to +150? lead temperature (soldering 10s) ..................................+300? electrical characteristics (v cc = +5v ?%, t a = t min to t max , unless otherwise noted. typical values are at v cc = +5v and t a = +25?.) (note 1) parameter symbol conditions min typ max units driver r diff = 100 , figure 1 2.0 v cc r diff = 54 , figure 1 1.5 differential driver output v od no load v cc v driver common-mode output voltage v oc r l = 100 or 54 , figure 1 v cc / 2 3 v driver disable threshold v dt figure 2 (note 2) +0.6 +1 v input-high voltage v ih di, shdn , re 2.0 v input-low voltage v il di, shdn , re 0.8 v input current i in di, shdn , re ? ? 0v v out +12v +50 +250 driver short-circuit output current (note 3) i osd -7v v out 0v -250 -50 ma (v cc - 1v) v out +12v 20 ma driver short-circuit foldback output current (note 3) i osdf -7v v out 0v -20 receiver v in = +12v 250 input current (a and b) i a, b di = v cc , v cc = gnd or +5v v in = -7v -200 ? receiver differential threshold voltage v th -7v v cm +12v -200 +200 mv receiver input hysteresis v th v a + v b = 0v 25 mv output-high voltage v oh i o = -1.6ma, v a - v b > v th v cc - 1.5 v output-low voltage v ol i o = 1ma, v a - v b < -v th 0.4 v tri-state output current at receiver i ozr 0v v o v cc ? ? receiver input resistance r in -7v v cm +12v 48 k receiver output short-circuit current i osr 0v v ro v cc ? ?5 ma
max13487e/max13488e half-duplex rs-485-/rs-422-compatible transceiver with autodirection control _______________________________________________________________________________________ 3 electrical characteristics (continued) (v cc = +5v ?%, t a = t min to t max , unless otherwise noted. typical values are at v cc = +5v and t a = +25?.) (note 1) parameter symbol conditions min typ max units power supply supply voltage v cc 4.75 5.25 v supply current i cc shdn = 1, re = 0, no load 4.5 ma shutdown supply current i shdn shdn = 0 10 a esd protection air gap discharge iec 61000-4-2 (max13487e) ?5 esd protection (a, b) human body model ?5 kv esd protection (all other pins) human body model ? kv switching characteristicsmax13487e (v cc = +5v ?%, t a = t min to t max , unless otherwise noted. typical values are at v cc = +5v and t a = +25?.) parameter symbol conditions min typ max units driver t dplh 200 1000 driver propagation delay t dphl r l = 110 , c l = 50pf, figures 2 and 3 200 1000 ns t hl 200 900 driver differential output rise or fall time t lh r l = 110 , c l = 50pf, figures 2 and 3 200 900 ns maximum data rate 500 kbps driver disable delay t ddd figure 3 2500 ns driver enable from shutdown to output high t dzh ( shdn ) figure 4 5.5 ? driver enable from shutdown to output low t dzl ( shdn ) figure 4 5.5 ? time to shutdown t shdn 50 340 700 ns receiver t rplh 80 receiver propagation delay t rphl c l = 15pf, figures 5 and 6 80 ns receiver output skew t rskew c l = 15pf, figure 6 13 ns maximum data rate 500 kbps receiver enable to output high t rzh figure 7 50 ns receiver enable to output low t rzl figure 7 50 ns receiver disable time from high t rhz figure 7 50 ns receiver disable time from low t rlz figure 7 50 ns receiver enable from shutdown to output high t rzh (shdn) figure 8 2200 ns
max13487e/max13488e half-duplex rs-485-/rs-422-compatible transceiver with autodirection control 4 _______________________________________________________________________________________ switching characteristicsmax13487e (continued) (v cc = +5v ?%, t a = t min to t max , unless otherwise noted. typical values are at v cc = +5v and t a = +25?.) parameter symbol conditions min typ max units receiver enable from shutdown to output low t rzl (shdn) figure 8 2200 ns receiver enable delay t red figure 3 70 ns time to shutdown t shdn 50 340 700 ns switching characteristicsmax13488e (v cc = +5v ?%, t a = t min to t max , unless otherwise noted. typical values are at v cc = +5v and t a = +25?.) parameter symbol conditions min typ max units driver t dplh 50 driver propagation delay t dphl r l = 110 , c l = 50pf, figures 2 and 3 50 ns t hl 15 driver differential output rise or fall time t lh r l = 110 , c l = 50pf, figures 2 and 3 15 ns maximum data rate 16 mbps driver disable delay t ddd figure 3 70 ns driver enable from shutdown to output high t dzh ( shdn ) figure 4 2.2 ? driver enable from shutdown to output low t dzl ( shdn ) figure 4 2.2 ? time to shutdown t shdn 50 340 700 ns receiver t rplh 80 receiver propagation delay t rphl c l = 15pf, figures 5 and 6 80 ns receiver output skew t rskew c l = 15pf, figure 6 13 ns maximum data rate 16 mbps receiver enable to output high t rzh figure 7 50 ns receiver enable to output low t rzl figure 7 50 ns receiver disable time from high t rhz figure 7 50 ns receiver disable time from low t rlz figure 7 50 ns receiver enable from shutdown to output high t rzh (shdn) figure 8 2200 ns
max13487e/max13488e half-duplex rs-485-/rs-422-compatible transceiver with autodirection control _______________________________________________________________________________________ 5 switching characteristicsmax13488e (continued) (v cc = +5v ?%, t a = t min to t max , unless otherwise noted. typical values are at v cc = +5v and t a = +25?.) parameter symbol conditions min typ max units receiver enable from shutdown to output low t rzl (shdn) figure 8 2200 ns receiver enable delay t red figure 3 70 ns time to shutdown t shdn 50 340 700 ns note 1: all currents into the device are positive. all currents out of the device are negative. all voltages referred to device ground, unless otherwise noted. note 2: this is a differential voltage from a to b that the driving device must see on the bus to disable its driver. note 3: the short-circuit output current applied to peak current just prior to foldback current limiting. the short-circuit foldback ou t- put current applies during current limiting to allow a recovery from bus contention. typical operating characteristics (v cc = +5.0v, t a = +25?, unless otherwise noted.) supply current vs. temperature max13487etoc01 temperature ( c) supply current (ma) 60 35 10 -15 3.2 3.4 3.6 3.8 4.0 3.0 -40 85 no load output current vs. receiver output-high voltage max13487etoc02 output-high voltage (v) output current (ma) 4 3 2 1 7 14 21 28 35 0 05 output current vs. receiver output-low voltage max13487etoc03 output-low voltage (v) output current (ma) 4 3 2 1 10 20 30 40 50 60 0 05 receiver output-high voltage vs. temperature max13487etoc04 temperature ( c) output-high voltage (v) 60 35 10 -15 4.2 4.6 4.4 4.8 5.0 5.2 5.4 4.0 -40 85 i o = 1ma receiver output-low voltage vs. temperature max13487etoc05 temperature ( c) output-low voltage (v) 60 35 10 -15 0.1 0.2 0.3 0.4 0.5 0 -40 85 i o = 1ma differential output current vs. differential output voltage max13487etoc06 output voltage (v) output current (ma) 4 3 2 1 20 40 60 80 0 05
max13487e/max13488e half-duplex rs-485-/rs-422-compatible transceiver with autodirection control 6 _______________________________________________________________________________________ driver differential output voltage vs. temperature max13487etoc07 temperature ( c) differential output voltage (v) 60 35 10 -15 0.5 1.0 1.5 2.0 2.5 3.0 0 -40 85 r diff = 54 output current vs. transmitter output-high voltage max13487etoc08 output-high voltage (v) output current (ma) 3 -1 -3 -5 1 4 02 -2 -4 -6 20 40 60 80 100 120 0 -7 5 output current vs. transmitter output-low voltage max13487etoc09 output-low voltage (v) output current (ma) 10 8 6 24 20 40 60 80 100 120 0 012 shutdown current vs. temperature max13487etoc10 temperature ( c) shutdown current ( a) 60 35 10 -15 2 1 4 6 8 3 5 7 9 10 0 -40 85 driver propagation vs. temperature (max13487e) max13487etoc12 temperature ( c) driver propagation delay (ns) 60 35 10 -15 200 100 300 400 500 600 0 -40 85 t dplh t dphl r l = 110 driver propagation vs. temperature (max13487e) max13487etoc11 temperature ( c) driver propagation delay (ns) 60 35 10 -15 200 400 600 800 1000 0 -40 85 t dplh t dphl r l = 10k receiver propagation vs. temperature (max13487e) max13487etoc15 temperature ( c) propagation delay (ns) 60 35 10 -15 15 30 45 60 0 -40 85 t rphl t rplh driver propagation vs. temperature (max13488e) max13487etoc13 temperature ( c) driver propagation delay (ns) 60 35 10 -15 10 5 15 20 25 30 0 -40 85 t dplh t dphl r l = 10k driver propagation vs. temperature (max13488e) max13487etoc14 temperature ( c) driver propagation delay (ns) 60 35 10 -15 10 5 15 20 25 30 0 -40 85 t dplh t dphl r l = 110 typical operating characteristics (continued) (v cc = +5.0v, t a = +25?, unless otherwise noted.)
max13487e/max13488e half-duplex rs-485-/rs-422-compatible transceiver with autodirection control _______________________________________________________________________________________ 7 typical operating characteristics (continued) (v cc = +5.0v, t a = +25?, unless otherwise noted.) receiver propagation vs. temperature (max13488e) max13487etoc16 temperature ( c) receiver propagation (ns) 60 35 10 -15 10 20 30 40 0 -40 85 t rplh t rphl driver propagation (500kbps) (max13487e) max13487etoc17 di 2v/div a-b 5v/div 400ns/div driver propagation (16mbps) (max13488e) max13487etoc18 di 2v/div a-b 5v/div 10ns/div waveform intensity: 68% receiver propagation (16mbps) (max13488e) max13487etoc19 b 2v/div ro 2v/div a 2v/div 10ns/div driving 16nf (19.2kbps) (max13487e) max13487etoc20 di 2v/div a-b 5v/div 10 s/div driving 16nf (19.2kbps) (max13488e) max13487etoc21 di 2v/div a-b 5v/div 10 s/div driving 16nf (750kbps) (max13488e) max13487etoc22 di 2v/div a-b 5v/div 400ns/div
max13487e/max13488e half-duplex rs-485-/rs-422-compatible transceiver with autodirection control 8 _______________________________________________________________________________________ v od c l r diff 2 r diff 2 v oc a b figure 1. driver dc test load a b di r l v id r l v cc gnd c l figure 2. driver-timing test circuit 1.5v 1.5v 0 di b a t dplh t dphl 1/2 v o 1/2 v o v o t ddd , t red ro (ro pulled low) 10% 90% 10% 90% 0 v o o -v o v diff v diff = v(a) - v(b) t hl t lh f = 1mhz, t lh 3ns, t hl 3ns v cc re = v cc figure 3. driver propagation delays test circuits and waveforms
max13487e/max13488e half-duplex rs-485-/rs-422-compatible transceiver with autodirection control _______________________________________________________________________________________ 9 t dzh(shdn) t dzl(shdn) 1.5v 2.3v 2.3v output normally high output normally low v cc v cc c l s 1 s 2 0 a, b 0 a, b v ol shdn 500 output under test figure 4. driver enable and disable times v id a b r receiver output ate figure 5. receiver-propagation-delay test circuit 1.5v 1.5v 1v -1v f = 1mhz, t lh 3ns, t hl 3ns t rphl t rskew = | t rphl - t rplh | t rplh v oh v ol ro a b figure 6. receiver propagation delays test circuits and waveforms (continued)
max13487e/max13488e half-duplex rs-485-/rs-422-compatible transceiver with autodirection control 10 ______________________________________________________________________________________ 1.5v 1.5v ro 0 0 output normally low ro output normally high t rzh(shdn) , t rzh t rhz t rhz 2.3v 2.3v v oh + 0.5v v oh + 0.5v di = 0v re v cc v cc v cc 0 t rzl(shdn) , t rzl figure 7. receiver enable and disable times t rzh(shdn) t rzl(shdn) 1.5v 2.3v 2.3v output normally high output normally low v cc v cc c l s 1 s 2 0 v cc 0 v cc 0 shdn 500 ro ro ro di = 1 figure 8. receiver enable time from shutdown test circuits and waveforms (continued)
max13487e/max13488e half-duplex rs-485-/rs-422-compatible transceiver with autodirection control ______________________________________________________________________________________ 11 pin description pin name function 1ro receiver output. when receiver is enabled and v(a) - v(b) > +200mv, ro is high. if v(a) - v(b) < -200mv, ro is low. 2 re receiver output enable. drive re low to enable the ro. drive re high to let the autodirection circuit control the receiver. re is a hot-swap input (see the hot-swap capability section for more details). 3 shdn shutdown. drive shdn high to let the device operate in normal operation. drive shdn low to put the part in shutdown. 4di driver input. drive di low to force noninverting output low and inverting output high. drive di high to force noninverting output high and inverting output low. di is an input to the internal state machine that automatically enables and disables the driver. see the function tables and general description for more information. di is a hot-swap input (see the hot-swap capability section for more details). 5 gnd ground 6 a noninverting receiver input and noninverting driver output 7 b inverting receiver input and inverting driver output 8v cc positive supply, v cc = +5v ?%. bypass v cc to gnd with a 0.1? capacitor. transmitting inputs outputs shdn di a-b > v dt action a b 1 0 x turn driver on 0 1 1 1 false if driver was off, keep it off high impedance high impedance 1 1 false if driver was on, keep it on 1 0 1 1 true turn driver off high impedance high impedance 0 x x x shutdown receiving inputs output shdn re a-b driver state receiver state ro 10 +200mv x on 1 10 -200mv x on 0 1 1 x on off high impedance 11 +200mv off on 1 11 -200mv off on 0 0 x x x x shutdown function tables x = don? care, shutdown mode, driver, and receiver outputs are in high impedance.
max13487e/max13488e detailed description the max13487e/max13488e half-duplex, high-speed transceivers for rs-485/rs-422 communication contain one driver and one receiver. the max13487e/ max13488e feature a hot-swap capability allowing line insertion without erroneous data transfer (see the hot- swap capability section). the max13487e features reduced slew-rate drivers that minimize emi and reduce reflections caused by improperly terminated cables, allowing error-free transmission up to 500kbps. the max13488e driver slew rate is not limited, making data throughput of up to 16mbps possible. autodirection circuitry internal circuitry in the max13487e/max13488e, in conjunction with an external pullup resistor on a and pulldown resistor on b (see typical application circuit ), act to automatically disable or enable the driver and receiver to keep the bus in the correct state. this autodirection circuitry consists of a state machine and an additional receive comparator that determines whether this device is trying to drive the bus, or another node on the network is driving the bus. the internal state machine has two inputs: ?i the current state of a-b (determined by a dedicated differential comparator) the state machine also has two outputs: driver_enable?nternal signal that enables and disables the driver receiver_enable?nternal signal that is the inverse of the driver_enable signal, but it can be overridden by an external pin when di is low, the device always drives the bus low. when di is high, the device drives the bus for a short time, then disables the driver and allows the external pullup/pulldown resistors to hold the bus in the high state (a-b > 200mv). during each low-to-high transition of di, the driver stays enabled until (a-b) > v dt , and then disables the driver, letting the pullup/pulldown resistors hold the a and b lines in the correct state. pullup and pulldown resistors the pullup and pulldown resistors on the a and b lines are required for proper operation of the device although their exact value is not critical. they function to hold the bus in the high state (a-b > 200mv) follow- ing a low-to-high transition. sizing of these resistors is determined in the same way as when using any other rs-485 driver and depends on how the line is terminat- ed and how many nodes are on the bus. the most important factor when sizing these resistors is to guar- antee that the idle voltage on the bus (a-b) is greater than 200mv in order to remain compatible with stan- dard rs-485 receiver thresholds. idle state when not transmitting data, the max13487e/ max13488e require the di input be driven high to remain in the idle state. a conventional rs-485 trans- ceiver has de and re inputs that are used to enable and disable the driver and receiver. however, the max13487e/max13488e does not have a de input, and instead uses an internal state machine to enable and disable the drivers. di must be driven high in order to go to the idle state. hot-swap capability hot-swap inputs when circuit boards are inserted into a hot or powered back plane, differential disturbances to the data bus can lead to data errors. upon initial circuit-board inser- tion, the data communication processor undergoes its own power-up sequence. during this period, the processor? logic-output drivers are high impedance and are unable to drive the di and re inputs of these devices to a defined logic level. leakage currents up to ?0? from the high-impedance state of the proces- sor? logic drivers could cause standard cmos enable inputs of a transceiver to drift to an incorrect logic level. additionally, parasitic circuit-board capacitance could cause coupling of v cc or gnd to the enable inputs. without the hot-swap capability, these factors could improperly enable the transceiver? driver. to overcome both these problems, two different pullup switches (strong and weak) are turned on during the power-up. when v cc rises, an internal power-up signal enables a strong pullup circuit. it holds di and re high with 1ma for 15?. once the timeout is expired, this strong pullup is switched off. a weak pullup (100?) remains active to overcome leakage on the pin. this second weak pullup disappears as soon as the micro- controller forces a low state on these pins. therefore, in normal operation (after the first activation), these pins can be considered as high-impedance pins (cmos inputs) without any pullup circuitry. the autodirection state machine is initialized, forcing the driver disabled. the receiver is enabled in autodirection mode. hot-swap input circuitry the enable inputs feature hot-swap capability. at the input there are two pmos devices, m1 and m2 (figure 9). when v cc ramps from zero, an internal 15? timer turns half-duplex rs-485-/rs-422-compatible transceiver with autodirection control 12 ______________________________________________________________________________________
on m2 and sets the sr latch, which also turns on m1. transistors m2, a 1.5ma current source, and m1, a 500? current source, pull re to v cc through a 5k resistor. m2 is designed to pull re to the disabled state against an external parasitic capacitance up to 100pf that can drive re high. after 15?, the timer deactivates m2 while m1 remains on, holding di high against three-state leakages that can drive re low. 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, re reverts to a standard, high-impedance cmos input. whenever v cc drops below 1v, the hot-swap input is reset. di has similar hot-swap circuitry. 15kv esd protection as with all maxim devices, esd-protection structures are incorporated on all pins to protect against electro- static discharges encountered during handling and assembly. the driver outputs and receiver inputs of the max13487e/max13488e have extra protection against static electricity. maxim? engineers have developed state-of-the-art structures to protect these pins against esd of ?5kv without damage. the esd structures withstand high esd in all states: normal operation, shut- down, and powered down. after an esd event, the max13487e/max13488e keep working without latchup or damage. esd protection can be tested in various ways. the transmitter outputs and receiver inputs of the max13487e/max13488e are characterized for protec- tion to the following limits: ?5kv using the human body model ?5kv using the air gap discharge method speci- fied in iec 61000-4-2 (max13487e only) esd test conditions esd performance depends on a variety of conditions. contact maxim for a reliability report that documents test setup, test methodology, and test results. human body model figure 10a shows the human body model, and figure 10b shows the current waveform it generates when dis- charged into a low impedance. this model consists of a 100pf capacitor charged to the esd voltage of inter- est, which is then discharged into the test device through a 1.5k resistor. iec 61000-4-2 the iec 61000-4-2 standard covers esd testing and performance of finished equipment. however, it does not specifically refer to integrated circuits. the max13487e/max13488e help you design equipment to meet iec 61000-4-2 without the need for additional esd-protection components. the major difference between tests done using the human body model and iec 61000-4-2 is higher peak current in iec 61000-4-2 because series resistance is lower in the iec 61000-4-2 model. hence, the esd withstand voltage measured to iec 61000-4-2 is gener- ally lower than that measured using the human body model. figure 10c shows the iec 61000-4-2 model, and figure 10d shows the current waveform for iec 61000-4-2 esd contact discharge test. machine model the machine model for esd tests all pins using a 200pf storage capacitor and zero discharge resistance. the objective is to emulate the stress caused when i/o pins are contacted by handling equipment during test and assembly. of course, all pins require this protec- tion, not just rs-485 inputs and outputs. the air-gap test involves approaching the device with a charged probe. the contact-discharge method connects the probe to the device before the probe is energized. max13487e/max13488e half-duplex rs-485-/rs-422-compatible transceiver with autodirection control ______________________________________________________________________________________ 13 v cc m1 m2 100 a 500 a 5k sr latch 15 s v cc timer timer re (hot swap) re figure 9. simplified structure of the receiver enable pin ( re )
max13487e/max13488e applications information 128 transceivers on the bus the standard rs-485 receiver input impedance is 12k (1-unit load), and the standard driver can drive up to 32-unit loads. the max13487e/max13488e have a 1/4- unit load receiver input impedance (48k ), allowing up to 128 transceivers to be connected in parallel on one communication line. any combination of these devices, as well as other rs-485 transceivers with a total of 32- unit loads or fewer, can be connected to the line. reduced emi and reflections the max13487e features reduced slew-rate drivers that minimize emi and reduce reflections caused by improperly terminated cables, allowing error-free data transmission up to 500kbps. low-power shutdown mode low-power shutdown mode is initiated by bringing shdn low. in shutdown, the devices draw a maximum of 10? of supply current. the devices are guaranteed not to enter shutdown if shdn is low for less than 50ns. if the inputs are in this state for at least 700ns, the devices are guaranteed to enter shutdown. enable times t zh and t zl (see the switching character- istics section) assume the devices were not in a low- power shutdown state. enable times t zh(shdn) and t zl(shdn) assume the devices were in shutdown state. it takes drivers and receivers longer to become enabled from low-power shutdown mode (t zh(shdn) , t zl(shdn) ) than from driver/receiver-disable mode (t zh , t zl ). line length the rs-485/rs-422 standard covers line lengths up to 4000ft. half-duplex rs-485-/rs-422-compatible transceiver with autodirection control 14 ______________________________________________________________________________________ charge-current- limit resistor discharge resistance storage capacitor c s 100pf r c 1m r d 1500 high- voltage dc source device under test figure 10a. human body esd test model i p 100% 90% 36.8% t rl time t dl current waveform peak-to-peak ringing (not drawn to scale) i r 10% 0 0 amps figure 10b. human body current waveform charge-current- limit resistor discharge resistance storage capacitor c s 150pf r c 50m to 100m r d 330 high- voltage dc source device under test figure 10c. iec 61000-4-2 esd test model t r = 0.7ns to 1ns 30ns 60ns t 100% 90% 10% i peak i figure 10d. iec 61000-4-2 esd generator current waveform
typical applications the max13487e/max13488e transceivers are designed for half-duplex, bidirectional data communi- cations on multipoint bus transmission lines. figure 11 shows a typical network application. to minimize reflec- tions, terminate the line at both ends in its characteristic impedance, and keep stub lengths off the main line as short as possible. the slew-rate-limited max13487e is more tolerant of imperfect termination. isolated rs-485 interface an isolated rs-485 interface electrically isolates differ- ent nodes on the bus to protect the bus from problems due to high common-mode voltages that exceed the rs-485 common-mode voltage range, conductive noise, and ground loops. the typical application circuit shows an isolated rs-485 interface using the max13487e/max13488e. the transceiver is powered separately from the controlling circuitry. the autodirection feature of the max13487e/max13488e (see the autodirection circuitry section), replaces an external relay allowing faster switching speeds, no con- tact bounce, better reliability, and better electrical isola- tion. the max13487e/max13488e only require two optocouplers to electrically isolate the transceiver. chip information process: bicmos max13487e/max13488e half-duplex rs-485-/rs-422-compatible transceiver with autodirection control ______________________________________________________________________________________ 15 r r r d d d di di ro ro re re r t r t r d di ro re di ro re shdn shdn max13487e max13488e v cc v cc v cc v cc shdn shdn figure 11. typical half-duplex rs-485 network
max13487e/max13488e half-duplex rs-485-/rs-422-compatible transceiver with autodirection control 16 ______________________________________________________________________________________ gnd di 1 2 8 7 v cc v iso v cc re shdn ro so 3 4 6 5 r d + rt b a 0.1 f v iso v iso v sys v sys rxd txd pin configuration/typical application circuit
max13487e/max13488e half-duplex rs-485-/rs-422-compatible transceiver with autodirection control 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 ____________________ 17 2007 maxim integrated products is a registered trademark of maxim integrated products, inc. boblet package information (the package drawing(s) in this data sheet may not reflect the most current specifications. for the latest package outline info rmation, go to www.maxim-ic.com/packages .) soicn .eps package outline, .150" soic 1 1 21-0041 b rev. document control no. approval proprietary information title: top view front view max 0.010 0.069 0.019 0.157 0.010 inches 0.150 0.007 e c dim 0.014 0.004 b a1 min 0.053 a 0.19 3.80 4.00 0.25 millimeters 0.10 0.35 1.35 min 0.49 0.25 max 1.75 0.050 0.016 l 0.40 1.27 0.394 0.386 d d min dim d inches max 9.80 10.00 millimeters min max 16 ac 0.337 0.344 ab 8.75 8.55 14 0.189 0.197 aa 5.00 4.80 8 n ms012 n side view h 0.244 0.228 5.80 6.20 e 0.050 bsc 1.27 bsc c h e e b a1 a d 0-8 l 1 variations:

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