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general description the MAX14852/max14854 isolated rs-485/rs-422 transceivers provide 2750v rms (60s) of galvanic isola - tion between the cable side (rs-485/rs-422 driver/ receiver side) and the uart side of the device. isolation improves communication by breaking ground loops and reduces noise when there are large differences in ground potential between ports. these devices allow for robust communication up to 500kbps (MAX14852) or 25mbps (max14854). the devices include one drive channel and one receive channel. the receiver is 1/4-unit load, allowing up to 128 transceivers on a common bus. integrated true fail-safe circuitry ensures a logic-high on the receiver output when inputs are shorted or open. undervoltage lockout disables the driver when cable side or uart-side power supplies are below functional levels. the driver outputs and receiver inputs are protected from 35kv electrostatic discharge (esd) to gndb on the cable side, as specified by the human body model (hbm). the MAX14852/max14854 are available in a wide-body 16-pin soic package and operate over the -40c to +105c temperature range. benefts and features high-performance transceiver enables flexible designs ? integrated ldo for cable side power ? compliant with rs-485 eia/tia-485 standard ? 500kbps (MAX14852)/25mbps (max14854) maximum data rate ? allows up to 128 devices on the bus integrated protection ensures for robust communication ? 35kv esd (hbm) on driver outputs/receiver inputs ? 2.75kv rms withstand isolation voltage for 60 seconds (v iso ) ? 630v peak maximum repetitive peak-isolation voltage (v iorm ) ? 445v rms maximum working-isolation voltage (v iowm ) ? > 30 years lifetime at rated working voltage ? withstands 10kv surge per iec 61000-4-5 ? thermal shutdown safety regulatory approvals pending ul according to ul1577 cul according to csa bulletin 5a vde 0884-10 applications industrial automation equipment programmable logic controllers hvac power meters ordering information appears at end of data sheet. 19-7965; rev 0; 11/15 ldo rs - 485 transceiver vdda rxd re txd de a b vddb vldo gnda gndb max 14852 max 14854 sba z y functional diagram evaluation kit available MAX14852/max14854 2.75kv rms isolated 500kbps/25mbps full-duplex rs-485/rs-422 transceivers with 35kv esd protection
v dda to gnda ....................................................... -0.3v to +6v v ddb to gndb ........................................................ -0.3v to +6v v ldo to gndb ...................................................... -0.3v to +16v txd, de, re to gnda ........................................... -0.3v to +6v sba , rxd to gnda ............................. -0.3v to (v dda + 0.3v) a, b, z, y to gndb .................................................. -8v to +13v short circuit duration (rxd, sba to gnda, a, b, y, z ,v ddb to gndb) .................................... continuous continuous power dissipation (t a = +70c) 16-pin wide soic (derate 14.1mw/c above +70c) .......................... 1126.8mw operating temperature range ......................... -40c to +105c junction temperature ...................................................... +150c storage temperature range ............................ -65c to +150c lead temperature (soldering, 10s) ................................. +300c soldering temperature (reflow) ....................................... +260c junction-to-ambient thermal resistance ( ja ) .............. 71c/w junction-to-case thermal resistance ( jc ) ................... 23c/w (note 1) dc electrical characteristics (v dda C v gnda = 1.71v to 5.5v, v ddb C v gndb = 3.0v to 5.5v, t a = t min to t max , unless otherwise noted. typical values are at v dda C v gnda = 3.3v, v ddb C v gndb = 3.3v, v gnda = v gndb , and t a = +25c.) (notes 2, 3) parameter symbol conditions min typ max units power supply voltage v dda 1.71 5.5 v v ddb 3.0 5.5 supply current i dda v dda = 5v, de = high, re = txd = low, rxd unconnected, no load 3.9 6.6 ma i ddb de = high, re = txd = low, rxd uncon- nected, no bus load, v ddb = 3.3v 7 12.5 undervoltage lockout thresh - old v uvloa v dda rising 1.50 1.58 1.65 v v uvlob v ddb rising 2.55 2.7 2.85 undervoltage lockout thresh - old hysteresis v uvhysta 50 mv v uvhystb 200 ldo ldo supply voltage v ldo relative to gndb, ldo is on (note 4) 3.18 14 v ldo supply current i ldo de = high, txd = low, no bus load, v ldo = 5.5v 7.5 12.9 ma ldo output voltage v ddb 3.0 3.3 3.6 v ldo current limit 300 ma load regulation v ldo = 3.3v, i load = 20ma to 40ma 0.19 1.7 mv/ma line regulation v ldo = 3.3v to 14v, i load = 20ma 0.12 1.8 mv/v dropout voltage v ldo = 3.18v, i ddb = -120ma 100 180 mv maxim integrated 2 note 1: package thermal resistances were obtained using the method described in jedec specification jesd51-7, using a four-layer board. for detailed information on package thermal considerations, refer to www.maximintegrated.com/thermal-tutorial . absolute maximum ratings stresses beyond those listed under absolute maximum ratings may cause permanent damage to the device. these are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. exposure to ab solute maximum rating conditions for extended periods may affect device reliability. package thermal characteristics www.maximintegrated.com MAX14852/max14854 2.75kv rms isolated 500kbps/25mbps full-duplex rs-485/rs-422 transceivers with 35kv esd protection
dc electrical characteristics (continued) (v dda C v gnda = 1.71v to 5.5v, v ddb C v gndb = 3.0v to 5.5v, t a = t min to t max , unless otherwise noted. typical values are at v dda C v gnda = 3.3v, v ddb C v gndb = 3.3v, v gnda = v gndb , and t a = +25c.) (notes 2, 3) parameter symbol conditions min typ max units load capacitance nominal value (note 7) 1 10 f logic interface (txd, rxd, de, re, sba) input high voltage v ih re , txd, de to gnda 2.25v v dda 5.5v 0.7 x v dda v 1.71v v dda 1.89v 0.78 x v dda input low voltage v il re , txd, de to gnda 2.25v v dda 5.5v 0.8 v 1.71v v dda 1.89v 0.6 input hysteresis v hys re , txd, de to gnda 220 mv input capacitance c in re , txd, de, f = 1mhz 2 pf input pullup current i pu txd -10 -4.5 -1.5 a input pulldown current i pd de, re 1.5 4.5 10 a sba pullup resistance r sba 3 5 8 k output voltage high v oh rxd to gnda, i out = -4ma v dda -0.4 v output voltage low v ol rxd to gnda, i out = 4ma 0.40 v sba to gnda, i out = 4ma 0.45 short-circuit output pullup current i sh_pu 0v v rxd v dda , (v a - v b ) > -10mv, re = low -42 ma short-circuit output pulldown current i sh_pd 0v v rxd v dda , (v a - v b ) < -200mv, re = low 40 ma 0v v v dda , side b is powered and working 60 three-state output current i oz 0v v rxd v dda , re = high -1 +1 a driver differential driver output |v od | r l = 54, txd = high or low, figure 1a 1.5 v r l = 100, txd = high or low, figure 1a 2.0 -7v v cm +12v, figure 1b 1.5 5 change in magnitude of differ - ential driver output voltage v od r l = 100 or 54, figure 1a (note 5) 0.2 v driver common-mode output voltage v oc r l = 100 or 54, figure 1a (note 5) v ddb / 2 3 v change in magnitude of common-mode voltage v oc r l = 100 or 54, figure 1a (note 5) 0.2 v maxim integrated 3 www.maximintegrated.com MAX14852/max14854 2.75kv rms isolated 500kbps/25mbps full-duplex rs-485/rs-422 transceivers with 35kv esd protection
dc electrical characteristics (continued) (v dda C v gnda = 1.71v to 5.5v, v ddb C v gndb = 3.0v to 5.5v, t a = t min to t max , unless otherwise noted. typical values are at v dda C v gnda = 3.3v, v ddb C v gndb = 3.3v, v gnda = v gndb , and t a = +25c.) (notes 2, 3) parameter symbol conditions min typ max units driver short-circuit output current i osd gndb v out +12v, output low (note 6) +30 +250 ma -7v v out v ddb , output high (note 6) -250 -30 single-ended driver output voltage high v oh y and z outputs, i y, z = -20ma 2.2 v single-ended driver output voltage low v ol y and z outputs, i y, z = +20ma 0.8 v differential driver output capacitance c od de = re = high, f = 4mhz 12 pf receiver input current (a and b) i a , i b de = low, v ddb = gndb or 3.6v v in = +12v +250 a v in = -7v -200 receiver differential threshold voltage v th -7v v cm +12v -200 -120 -10 mv receiver input hysteresis v th v cm = 0v 20 mv receiver input resistance r in -7v v cm +12v, de = low 48 k differential input capacitance c a,b measured between a and b, de = re = low at 6mhz 12 pf protection thermal-shutdown threshold t shdn temperature rising +160 c thermal-shutdown hysteresis t hyst 15 c esd protection (a and b pins to gndb) human body model 35 kv iec 61000-4-2 air gap discharge 18 iec 61000-4-2 contact discharge 8 esd protection (all other pins) human body model 4 kv maxim integrated 4 www.maximintegrated.com MAX14852/max14854 2.75kv rms isolated 500kbps/25mbps full-duplex rs-485/rs-422 transceivers with 35kv esd protection
switching electrical characteristics (MAX14852) (v dda C v gnda = 1.71v to 5.5v, v ddb C v gndb = 3.0v to 5.5v, t a = t min to t max , unless otherwise noted. typical values are at v dda C v gnda = 3.3v, v ddb C v gndb = 3.3v, v gnda = v gndb , and t a = +25c.) (note 7) parameter symbol conditions min typ max units dynamic common mode transient immunity cmti (note 8) 35 kv/s glitch rejection txd, de, rxd 10 17 29 ns driver driver propagation delay t dplh, t dphl r l = 54, c l = 50pf, figure 2 and figure 3 1040 ns differential driver output skew |t dplh - t dphl | t dskew r l = 54, c l = 50pf, figure 2 and figure 3 144 ns driver differential output rise or fall time t lh , t hl r l = 54, c l = 50pf, figure 2 and figure 3 900 ns maximum data rate dr max 500 kbps driver enable to output high t dzh r l = 110, c l = 50pf, figure 5 2540 ns driver enable to output low t dzl r l = 110, c l = 50pf, figure 5 2540 ns driver disable time from low t dlz r l = 110, c l = 50pf, figure 5 140 ns driver disable time from high t dhz r l = 110, c l = 50pf, figure 4 140 ns receiver receiver propagation delay t rplh, t rphl c l = 15pf, figure 6 and figure 7 (note 9) 240 ns receiver output skew |t rplh - t rphl | t rskew c l = 15pf, figure 6 and figure 7 (note 9) 34 ns maximum data rate dr max 500 kbps receiver enable to output high t rzh r l = 1k, c l = 15pf, s2 closed, figure 8 20 ns receiver enable to output low t rzl r l = 1k, c l = 15pf, s1 closed, figure 8 30 ns receiver disable time from low t rlz r l = 1k, c l = 15pf, s1 closed, figure 8 20 ns receiver disable time from high t rhz r l = 1k, c l = 15pf, s2 closed, figure 8 20 ns maxim integrated 5 www.maximintegrated.com MAX14852/max14854 2.75kv rms isolated 500kbps/25mbps full-duplex rs-485/rs-422 transceivers with 35kv esd protection
note 2: all devices are 100% production tested at t a = +25c. specifications over temperature are guaranteed by design. note 3: all currents into the device are positive. all currents out of the device are negative. all voltages are referenced to their respective ground (gnda or gndb), unless otherwise noted. note 4: v ldo max indicates voltage capability of the circuit. power dissipation requirements may limit v ldo max to a lower value. note 5: v od and v oc are the changes in v od and v oc , respectively, when the txd input changes state. note 6: the short circuit output current applies to the peak current just prior to current limiting. note 7: not production tested. guaranteed by design. note 8: cmti is the maximum sustainable common-mode voltage slew rate while maintaining the correct output states. cmti applies to both rising and falling common-mode voltage edges. tested with the transient generator connected between gnda and gndb. v cm = 1kv note 9: capacitive load includes test probe and fixture capacitance. switching electrical characteristics (max14854) (v dda C v gnda = 1.71v to 5.5v, v ddb C v gndb = 3.0v to 5.5v, t a = t min to t max , unless otherwise noted. typical values are at v dda C v gnda = 3.3v, v ddb C v gndb = 3.3v, v gnda = v gndb , and t a = +25c.) (note 7) parameter symbol conditions min typ max units dynamic common mode transient immunity cmti (note 8) 35 kv/s glitch rejection txd, de, rxd 10 17 29 ns driver driver propagation delay t dplh, t dphl r l = 54, c l = 50pf, figure 2 and figure 3 65 ns differential driver output skew |t dplh - t dphl | t dskew r l = 54, c l = 50pf, figure 2 and figure 3 7 ns driver differential output rise or fall time t lh , t hl r l = 54, c l = 50pf, figure 2 and figure 3 10 ns maximum data rate dr max 25 mbps driver enable to output high t dzh r l = 110, c l = 50pf, figure 4 80 ns driver enable to output low t dzl r l = 110, c l = 50pf, figure 5 80 ns driver disable time from low t dlz r l = 110, c l = 50pf, figure 5 80 ns driver disable time from high t dhz r l = 110, c l = 50pf, figure 4 80 ns receiver receiver propagation delay t rplh, t rphl c l = 15pf, figure 6 and figure 7 (note 9) 65 ns receiver output skew |t rplh - t rphl | t rskew c l = 15pf, figure 6 and figure 7 (note 9) 7 ns maximum data rate dr max 25 mbps receiver enable to output high t rzh r l = 1k, c l = 15pf, s2 closed, figure 8 20 ns receiver enable to output low t rzl r l = 1k, c l = 15pf, s1 closed, figure 8 30 ns receiver disable time from low t rlz r l = 1k, c l = 15pf, s1 closed, figure 8 20 ns receiver disable time from high t rhz r l = 1k, c l = 15pf, s2 closed, figure 8 20 ns maxim integrated 6 www.maximintegrated.com MAX14852/max14854 2.75kv rms isolated 500kbps/25mbps full-duplex rs-485/rs-422 transceivers with 35kv esd protection
note 10: v iorm , v iowm , and v iso are defined by the iec 60747-5-5 standard. note 11: product is qualified at v iso for 60 seconds. 100% production tested at 120% of v iso for 1 second. ul the MAX14852/max14854 is certifed under ul1577. for more details, see file e351759. rate up to 2750v rms isolation voltage for basic insulation. cul pending vde pending tuv pending parameter symbol conditions value units partial discharge test voltage v pr method b1 = v iorm x 1.875 (t = 1s, par - tial discharge < 5pc) 1182 v p maximum repetitive peak withstand voltage v iorm (note 7) 630 v p maximum working isolation voltage v iowm (note 7) 445 v rms maximum transient isolation voltage v iotm t = 1s 4600 v p maximum withstand isolation voltage v iso t = 60s, f = 60hz (note 7, 8) 2750 v rms maximum surge isolation voltage v iosm iec 61000-4-5, 1.2/50 s 10 kv insulation resistance r s t a = +150c, v io = 500v >10 9 barrier capacitance input to output cio 2 pf creepage distance cpg wide so 8 mm clearance distance clr wide so 8 mm internal clearance distance through insulation 0.015 mm comparitive tracking resistance index cti material group ii (iec 60112) 575 climatic category 40/125/21 pollution degree ( din vde 0110, table 1) 2 maxim integrated 7 insulation characteristics safety regulatory approvals (pending) www.maximintegrated.com MAX14852/max14854 2.75kv rms isolated 500kbps/25mbps full-duplex rs-485/rs-422 transceivers with 35kv esd protection
figure 1. driver dc test load r l 2 r l 2 v oc v od y z ( a ) 375 ? v cm y z ( b ) 375 ? + - 60 ? v od r l c l v od txd gnda y z 50% 50% gnda txd z y 20% 80% 20% 80% 0 v o -v o v diff t dskew = |t dplh - t dphl | v diff = v y - v z v dda t lh p 3ns, t hl p 3ns 1/2 v o t dplh t lh t hl t dphl v o 1/2 v o figure 2. driver timing test circuit figure 3. driver propagation delays maxim integrated 8 www.maximintegrated.com MAX14852/max14854 2.75kv rms isolated 500kbps/25mbps full-duplex rs-485/rs-422 transceivers with 35kv esd protection
figure 4. driver enable and disable times (t dhz , t dzh ) figure 5. driver enable and disable times (t dzl , t dlz ) gnda gndb 250mv 50% t dzh t dhz de v dda v oh 50% out r l = 500i 50i out s1 y z d txd gnda or v dda gnda gndb generator de c l 50pf r l = 500i c l = 50pf 50i gndb gnda out gnda 250mv 50% t dzl t dlz de s1 y z d txd gnda or v dda v ddb v dda 50% out v ddb v ol generator de figure 6. receiver propagation delay test circuit v id b a receiver output ate r maxim integrated 9 www.maximintegrated.com MAX14852/max14854 2.75kv rms isolated 500kbps/25mbps full-duplex rs-485/rs-422 transceivers with 35kv esd protection
figure 7. receiver propagation delays a b v oh v ol rxd t rphl t rskew = |t rphl - t rplh | t lh p 3ns, t hl p 3ns t rplh -1v 1v 2 v dda 2 v dda figure 8. receiver enable and disable times generator 50i r l 1ki c l 15pf r -1.5v +1.5v rxd s1 v dda gnda gndb gnda s2 s3 v id re re rxd re rxd re re rxd rxd gnda t rhz t rlz 0.25v 0.25v 50% 50% gnda gnda 2 s1 open s2 closed s3 = +1.5v s1 open s2 closed s3 = +1.5v s1 closed s2 open s3 = -1.5v s1 closed s2 open s3 = -1.5v v oh gnda gnda v oh v dda v dda v dda 50% 50% v dda t rzl v ol gnda v dda v dda v dda v ol t rzh 2 v dda maxim integrated 10 www.maximintegrated.com MAX14852/max14854 2.75kv rms isolated 500kbps/25mbps full-duplex rs-485/rs-422 transceivers with 35kv esd protection
(v dda C v gnda = 3.3v, v ddb C v gndb = 3.3v, v gnda = v gndb , and t a = +25c, unless otherwise noted.) 0 100 200 300 400 500 600 700 800 900 1000 -45 -30 -15 0 15 30 45 60 75 90 105 propagation delay (ns) temperature ( c) MAX14852 transmitter propagation delay vs. temperature toc04 r l = 54 ? c l = 50pf t pdhl t pdlh 0 1 2 3 4 5 6 7 8 -45 -30 -15 0 15 30 45 60 75 90 105 i dda (ma) temperature ( c) v dda supply current vs. temperature toc01 no load no switching MAX14852 driver propagation delay txd 2v/div 0v y 1v/div z 1v/div toc07 100ns/div v outn v inside v backup r l = 54 ? c l = 50pf 0 2 4 6 8 10 12 14 -45 -30 -15 0 15 30 45 60 75 90 105 i ddb (ma) temperature ( c) v ddb supply current vs. temperature toc02 no load no switching MAX14852 receiver propagation delay rxd 2v/div 0v b 1v/div a 1v/div toc08 100ns/div c l = 15pf 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 -45 -30 -15 0 15 30 45 60 75 90 105 vod (v) temperature ( c) differential output voltage vs. temperature toc03 no load 120? load 54? load 0 5 10 15 20 25 30 35 40 45 50 55 60 65 -45 -30 -15 0 15 30 45 60 75 90 105 propagation delay (ns) temperature ( c) max14854 transmitter propagation delay vs. temperature toc09 r l = 54 ? c l = 50pf t pdhl t pdlh 0 20 40 60 80 100 120 140 160 180 200 220 240 -45 -30 -15 0 15 30 45 60 75 90 105 propagation delay (ns) temperature ( c) MAX14852 receiver propagation delay vs. temperature toc05 t rphl t rplh c l = 15pf 0 100 200 300 400 500 600 700 800 900 1000 -45 -30 -15 0 15 30 45 60 75 90 105 enable/disable delay (ns) temperature ( c) MAX14852 driver enable/disable delay vs. temperature toc06 t dzh t dzl t dhz t dlz maxim integrated g 11 7slfdo2shudwljkdudfwhulvwlfv www.maximintegrated.com MAX14852/max14854 2.75kv rms isolated 500kbps/25mbps full-duplex rs-485/rs-422 transceivers with 35kv esd protection
(v dda C v gnda = 3.3v, v ddb C v gndb = 3.3v, v gnda = v gndb , and t a = +25c, unless otherwise noted.) max14854 driver propagation delay txd 2v/div 0v y 1v/div z 1v/div toc12 10ns/div v outn v inside v backup r l = 54 ? c l = 50pf 0 5 10 15 20 25 30 35 40 45 50 55 60 65 -45 -30 -15 0 15 30 45 60 75 90 105 propagation delay (ns) temperature ( c) max14854 receiver propagation delay vs. temperature toc10 t rphl t rplh c l = 15pf 0 2 4 6 8 10 12 14 16 18 20 -45 -30 -15 0 15 30 45 60 75 90 105 enable/disable delay (ns) temperature ( c) receiver enable/disable delay vs. temperature toc14 t rzh t rzl t rhz t rlz 0 10 20 30 40 50 60 70 80 -45 -30 -15 0 15 30 45 60 75 90 105 enable/disable delay (ns) temperature ( c) max14854 driver enable/disable delay vs. temperature toc11 t dzh t dzl t dhz t dlz 0 1 2 3 4 5 6 7 8 0 5 10 15 20 25 i dda (ma) data rate (mbps) v dda supply current vs. data rate toc15 max14854 receiver propagation delay a 1v/div b 1v/div rxd 2v/div toc13 10ns/div v outn v inside v backup 0v c l = 15pf 0 10 20 30 40 50 60 70 0 5 10 15 20 25 i ddb (ma) data rate (mbps) v ddb supply current vs. data rate toc16 no load 54? load 120? load maxim integrated 12 7slfdo2shudwljkdudfwhulvwlfvfrwlxhg www.maximintegrated.com MAX14852/max14854 2.75kv rms isolated 500kbps/25mbps full-duplex rs-485/rs-422 transceivers with 35kv esd protection
pin name reference function 1 v dda gnda uart/logic-side power input. bypass v dda to gnda with both 0.1 f and 1f capacitors as close to the device as possible. 2, 8 gnda - uart/logic-side ground. gnda is the ground reference for digital signals. 3 rxd gnda receiver data output. drive re low to enable rxd. with re low, rxd is high when (v a C v b ) > -10mv and is low when (v a C v b ) < -200mv. rxd is high when v ddb is less than v uvlob . rxd is high impedance when re is high. 4 re gnda receiver output enable. driver re low or connect to gnda to enable rxd. drive re high to disable rxd. rxd is high-impedance when re is high. re has an internal 4.5a pull- down to gnda. 5 de gnda driver output enable. drive de high to enable bus driver outputs y and z. drive de low or connect to gnda to disable y and z. y and z are high impedance when de is low. de has an internal 4.5a pull-down to gnda. 6 txd gnda driver input. with de high, a low on txd forces the noninverting output (y) low and the inverting output (z) high. similarly, a high on txd forces the noninverting output high and the inverting output low. txd has an internal 4.5a pull-up to v dda . 7 sba gnda side b active indicator output. sba asserts low when side b is powered and working. sba has an internal 5k pull-up resistor to v dda . wide soic a b re 1 2 16 15 v ddb gndb gnda rxd v dda top view 3 4 14 13 y v ldo sba 5 12 z de txd 6 7 11 10 gndb gnda 8 9 max 14852 max 14854 + maxim integrated 13 pin confguration pin description www.maximintegrated.com MAX14852/max14854 2.75kv rms isolated 500kbps/25mbps full-duplex rs-485/rs-422 transceivers with 35kv esd protection
pin name reference function 9, 15 gndb - cable side ground. gndb is the ground reference for the internal ldo and the rs-485/ rs-422 bus signals. 10 v ldo gndb ldo power input. connect a minimum voltage of 3.18v to v ldo to power the cable side of the transceiver. bypass v ldo to gndb with both 0.1f and 1f capacitors as close to the device as possible. to disable the internal ldo, leave v ldo unconnected or connect to gndb. 11 y gndb noninverting driver output 12 z gndb inverting driver output 13 b gndb inverting receiver input 14 a gndb noninverting receiver input 16 v ddb gndb cable side power input/isolated ldo power output. bypass v ddb to gndb with both 0.1f and 1f capacitor as close to the device as possible. v ddb is the output of the internal ldo when power is applied to v ldo . when the internal ldo is not used (v ldo is unconnected or connected to gndb), v ddb is the positive supply input for the cable side of the ic. maxim integrated 14 pin description (continued) www.maximintegrated.com MAX14852/max14854 2.75kv rms isolated 500kbps/25mbps full-duplex rs-485/rs-422 transceivers with 35kv esd protection
* note: drive de low to disable the transmitter outputs. drive de high to enable the transmitter outputs. de has an internal pull-down to gnda. x = dont care *note: drive re high to disable the receiver output. drive re low to enable to receiver output. re has an internal pull-down to gnda. x = dont care function tables transmitting inputs outputs v dda v ddb de txd y z v uvloa v uvlob 1 1 1 0 v uvloa v uvlob 1 0 0 1 v uvloa v uvlob 0 x high-z high-z < v uvloa v uvlob x x high-z high-z v uvloa < v uvlob x x high-z high-z < v uvloa < v uvlob x x high-z high-z receiving inputs outputs v dda v ddb re (v a - v b ) rxd v uvloa v uvlob 0 > -10mv 1 v uvloa v uvlob 0 < -200mv 0 v uvloa v uvlob 0 open/short 1 v uvloa v uvlob 1 x high-z < v uvloa v uvlob x x high-z v uvloa < v uvlob 0 x 1 < v uvloa < v uvlob x x high-z sba v dda v ddb sba < v uvloa < v uvlob high < v uvloa v uvlob high v uvloa < v uvlob high v uvloa v uvlob low maxim integrated 15 www.maximintegrated.com MAX14852/max14854 2.75kv rms isolated 500kbps/25mbps full-duplex rs-485/rs-422 transceivers with 35kv esd protection
detailed description the MAX14852/max14854 isolated rs-485/rs-422 transceivers provide 5000v rms (60s) of galvanic isolation between the rs-485/rs-422 cable side of the transceiver and the uart side. these devices allow up to 500kbps (MAX14852)/25mbps (max14854) communication across an isolation barrier when a large potential exists between grounds on each side of the barrier. isolation data isolation is achieved using high-voltage capacitors that allow data transmission between the uart side and the rs-485/rs-422 cable side of the transceiver. integrated ldo the devices include an internal low-dropout regulator with a set 3.3v (typ) output that is used to power the cable side of the ic. the output of the ldo is v ddb . the ldo has a 300ma (typ) current limit. if the ldo is unused, connect v ldo to gndb and apply +3.3v directly to v ddb . true fail-safe the devices guarantee a logic-high on the receiver output when the receiver inputs are shorted or open, or when connected to a terminated transmission line with all drivers disabled. the receiver threshold is fixed between -10mv and -200mv. if the differential receiver input voltage (v a C v b ) is greater than or equal to -10mv, rxd is logic- high. in the case of a terminated bus with all transmitters disabled, the receivers differential input voltage is pulled to zero by the termination resistors. due to the receiver thresholds of the devices, this results in a logic-high at rxd. driver output protection two mechanisms prevent excessive output current and power dissipation caused by faults or bus contention. the first, a current limit on the output stage, provides immediate protection against short circuits over the entire common-mode voltage range. the second, a thermal- shutdown circuit, forces the driver outputs into a high-impedance state if the die temperature exceeds +160c (typ). thermal shutdown the devices are protected from overtemperature damage by integrated thermal-shutdown circuitry. when the junction temperature (t j ) exceeds +160c (typ), the driver outputs go high-impedance. the device resumes normal operation when t j falls below +145c (typ). applications information 128 transceivers on the bus the standard rs-485 receiver input impedance is one unit load. a standard driver can drive up to 32 unit-loads. the MAX14852/max14854 transceivers have a 1/4-unit load receiver, which allows up to 128 transceivers, connected in parallel, on one communication line. connect any combination of these devices, and/or other rs-485 devices, for a maximum of 32 unit-loads to the line. typical application the MAX14852/max14854 full-duplex transceivers are designed for bidirectional data communications on multi- point bus transmission lines. figure 9 and figure 10 show typical network application circuits. to minimize reflections, the bus should be terminated at both ends in its characteristics impedance, and stub lengths off the main line should be kept as short as possible. maxim integrated 16 www.maximintegrated.com MAX14852/max14854 2.75kv rms isolated 500kbps/25mbps full-duplex rs-485/rs-422 transceivers with 35kv esd protection
figure 9. typical isolated full-duplex rs-485/rs-422 application rxd re txd de rs - 485 transceiver y z rxd re txd de rs - 485 transceiver a b rxd re txd de rs - 485 transceiver a b rxd re txd de rs - 485 transceiver a b 120 ? integrated isolation barrier max 14852 max 14854 master slave slave slave figure 10. typical isolated point-to-point application rxd re txd de rs - 485 transceiver y z max 14852 max 14854 v ldo v ddb v dda 1 1 2 2 1 uf 1 uf 2 1 uf ldo 1 0 . 1 uf 2 0 . 1 uf 1 uf rxd re txd de rs - 485 transceiver a b v ddb v dda 3 3 4 4 1 uf v ldo 1 uf 3 max 14852 max 14854 3 0 . 1 uf 0 . 1 uf 4 ldo 2 0 . 1 uf 3 0 . 1 uf 120 ? 120 ? a b y z maxim integrated 17 www.maximintegrated.com MAX14852/max14854 2.75kv rms isolated 500kbps/25mbps full-duplex rs-485/rs-422 transceivers with 35kv esd protection
layout considerations it is recommended to design an isolation, or keep-out, channel underneath the isolator that is free from ground and signal planes. any galvanic or metallic connection between the cable side and uart side will defeat the isolation. ensure that the decoupling capacitors between v dda and gnda and between v ldo , v ddb , and gndb are located as close as possible to the ic to minimize inductance. route important signal lines close to the ground plane to minimize possible external influences. on the cable side of the devices, it is good practice to have the bus connec - tors and termination resistor as close as possible to the a and b pins. extended esd protection esd protection structures are incorporated on all pins to protect against electrostatic discharge encountered during handling and assembly. the driver outputs and receiver inputs of the devices have extra protection against static electricity to both the uart side and cable side ground references. the esd structures withstand high-esd events during normal operation and when pow- ered down. after an esd event, the devices keep working without latch-up or damage. bypass v dda to gnda and bypass v ddb and v ldo to gndb with 0.1f and 1f capacitors to ensure maximum esd protection. esd protection can be tested in various ways. the transmitter outputs and receiver inputs of the MAX14852/ max14854 are characterized for protection to the cable side ground (gndb) to the following limits: 35kv hbm 18kv using the air-gap discharge method specifed in iec 61000-4-2 8kv using the contact discharge method specifed in iec 61000-4-2 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 (hbm) figure 11 shows the hbm test model, while figure 12 shows the current waveform it generates when dis- charged in a low-impedance state. this model consists of a 100pf capacitor charged to the esd voltage of interest, 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 devices help in designing equipment to meet iec 61000-4-2 without the need for additional esd protection components. the major difference between tests done using the hbm 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 generally lower than that measured using the hbm. figure 13 shows the iec 61000-4-2 model and figure 14 shows the current waveform for iec 61000-4-2 esd contact discharge test. maxim integrated 18 www.maximintegrated.com MAX14852/max14854 2.75kv rms isolated 500kbps/25mbps full-duplex rs-485/rs-422 transceivers with 35kv esd protection
figure 11. human body esd test model figure 12. human body current waveform charge-current- limit resistor discharge resistance storage capacitor c s 100pf r c 1m r d 1500 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% 0 0 amps figure 13. iec 61000-4-2 esd test model figure 14. iec 61000-4-2 esd generator 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 t r = 0.7ns to 1ns 30ns 60ns t 100% 90% 10% i peak i maxim integrated 19 www.maximintegrated.com MAX14852/max14854 2.75kv rms isolated 500kbps/25mbps full-duplex rs-485/rs-422 transceivers with 35kv esd protection
ldo rs-485 transceiver v dda rxd txd de a b v ddb v ldo gnda gndb MAX14852 max14854 re isolation barrier uc z y sba typical application circuit maxim integrated 20 www.maximintegrated.com MAX14852/max14854 2.75kv rms isolated 500kbps/25mbps full-duplex rs-485/rs-422 transceivers with 35kv esd protection
package information for the latest package outline information and land patterns (footprints), go to www.maximintegrated.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. 16 soic w16m+9 21-0042 90-0107 ordering information part temp range pin-package MAX14852gwe+ -40c to +105c 16 soic (w) MAX14852gwe+t -40c to +105c 16 soic (w) max14854gwe+ -40c to +105c 16 soic (w) max14854gwe+t -40c to +105c 16 soic (w) +denotes a lead(pb)-free/rohs-compliant package. t = tape and reel. maxim integrated 21 chip information process: bicmos www.maximintegrated.com MAX14852/max14854 2.75kv rms isolated 500kbps/25mbps full-duplex rs-485/rs-422 transceivers with 35kv esd protection
revision history revision number revision date description pages changed 0 11/15 initial release ? 2015 maxim integrated products, inc. 22 maxim integrated cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a maxim integrated product. no circuit patent licenses are implied. maxim integrated reserves the right to change the circuitry and specifcations without notice at any time. the parametric values (min and max limits) shown in the electrical characteristics table are guaranteed. other parametric values quoted in this data sheet are provided for guidance. maxim integrated and the maxim integrated logo are trademarks of maxim integrated products, inc. MAX14852/max14854 2.75kv rms isolated 500kbps/25mbps full-duplex rs-485/rs-422 transceivers with 35kv esd protection for pricing, delivery, and ordering information, please contact maxim direct at 1-888-629-4642, or visit maxim integrateds website at www.maximintegrated.com.

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