(3.13)--MAX485建筑电气与智能化专业实训.pdf

For free samples&the latest literature:http:/www.maxim-,or phone 1-800-998-8800_General DescriptionThe MAX481,MAX483,MAX485,MAX487MAX491,andMAX1487 are low-power transceivers for RS-485 and RS-422 communication.Each part contains one driver and onereceiver.The MAX483,MAX487,MAX488,and MAX489feature reduced slew-rate drivers that minimize EMI andreduce reflections caused by improperly terminated cables,thus allowing error-free data transmission up to 250kbps.The driver slew rates of the MAX481,MAX485,MAX490,MAX491,and MAX1487 are not limited,allowing them totransmit up to 2.5Mbps.These transceivers draw between 120A and 500A ofsupply current when unloaded or fully loaded with disableddrivers.Additionally,the MAX481,MAX483,and MAX487have a low-current shutdown mode in which they consumeonly 0.1A.All parts operate from a single 5V supply.Drivers are short-circuit current limited and are protectedagainst excessive power dissipation by thermal shutdowncircuitry that places the driver outputs into a high-imped-ance state.The receiver input has a fail-safe feature thatguarantees a logic-high output if the input is open circuit.The MAX487 and MAX1487 feature quarter-unit-loadreceiver input impedance,allowing up to 128 MAX487/MAX1487 transceivers on the bus.Full-duplex communi-cations are obtained using the MAX488MAX491,whilethe MAX481,MAX483,MAX485,MAX487,and MAX1487are designed for half-duplex applications._ApplicationsLow-Power RS-485 TransceiversLow-Power RS-422 TransceiversLevel TranslatorsTransceivers for EMI-Sensitive ApplicationsIndustrial-Control Local Area Networks_Featureso In MAX Package:Smallest 8-Pin SOo Slew-Rate Limited for Error-Free DataTransmission(MAX483/487/488/489)o 0.1A Low-Current Shutdown Mode(MAX481/483/487)o Low Quiescent Current:120A(MAX483/487/488/489)230A(MAX1487)300A(MAX481/485/490/491)o-7V to+12V Common-Mode Input Voltage Rangeo Three-State Outputso 30ns Propagation Delays,5ns Skew(MAX481/485/490/491/1487)o Full-Duplex and Half-Duplex Versions Availableo Operate from a Single 5V Supplyo Allows up to 128 Transceivers on the Bus(MAX487/MAX1487)o Current-Limiting and Thermal Shutdown forDriver Overload Protection_Ordering InformationOrdering Information continued at end of data sheet.*Contact factory for dice specifications.MAX481/MAX483/MAX485/MAX487MAX491/MAX1487Low-Power,Slew-Rate-LimitedRS-485/RS-422 Transceivers_Maxim Integrated Products1MAX481?MAX483?MAX485?MAX487?MAX488?MAX489?MAX490?MAX491?MAX1487PART?NUMBERHALF/FULL?DUPLEXDATA RATE?(Mbps)SLEW-RATE?LIMITEDLOW-POWER?SHUTDOWNRECEIVER/?DRIVER?ENABLEQUIESCENT?CURRENT?(A)NUMBER OF?TRANSMITTERS?ON BUSPIN?COUNTHalf?Half?Half?Half?Full?Full?Full?Full?Half2.5?0.25?2.5?0.25?0.25?0.25?2.5?2.5?2.5No?Yes?No?Yes?Yes?Yes?No?No?NoYes?Yes?No?Yes?No?No?No?No?NoYes?Yes?Yes?Yes?No?Yes?No?Yes?Yes300?120?300?120?120?120?300?300?23032?32?32?128?32?32?32?32?1288?8?8?8?8?14?8?14?8_Selection Table19-0122;Rev 5;2/96PARTTEMP.RANGEPIN-PACKAGEMAX481CPA0C to+70C8 Plastic DIPMAX481CSA0C to+70C8 SOMAX481CUA0C to+70C8 MAXMAX481C/D0C to+70CDice*MAX481/MAX483/MAX485/MAX487MAX491/MAX1487Low-Power,Slew-Rate-LimitedRS-485/RS-422 Transceivers2_ABSOLUTE MAXIMUM RATINGSSupply Voltage(VCC).12VControl Input Voltage(RE,DE).-0.5V to(VCC+0.5V)Driver Input Voltage(DI).-0.5V to(VCC+0.5V)Driver Output Voltage(A,B).-8V to+12.5VReceiver Input Voltage(A,B).-8V to+12.5VReceiver Output Voltage(RO).-0.5V to(VCC+0.5V)Continuous Power Dissipation(TA=+70C)8-Pin Plastic DIP(derate 9.09mW/C above+70C).727mW14-Pin Plastic DIP(derate 10.00mW/C above+70C).800mW8-Pin SO(derate 5.88mW/C above+70C).471mW14-Pin SO(derate 8.33mW/C above+70C).667mW8-Pin MAX(derate 4.1mW/C above+70C).830mW8-Pin CERDIP(derate 8.00mW/C above+70C).640mW14-Pin CERDIP(derate 9.09mW/C above+70C).727mWOperating Temperature RangesMAX4_ _C_ _/MAX1487C_ A.0C to+70CMAX4_ _E_ _/MAX1487E_ A.-40C to+85CMAX4_ _MJ_/MAX1487MJA.-55C to+125CStorage Temperature Range.-65C to+160CLead Temperature(soldering,10sec).+300CDC ELECTRICAL CHARACTERISTICS(VCC=5V 5%,TA=TMINto TMAX,unless otherwise noted.)(Notes 1,2)Stresses beyond those listed under“Absolute Maximum Ratings”may cause permanent damage to the device.These are stress ratings only,and functionaloperation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied.Exposure toabsolute maximum rating conditions for extended periods may affect device reliability.VVIN=-7VVIN=12VVIN=-7VVIN=12VInput Current(A,B)IIN2VTHk48-7V VCM 12V,MAX487/MAX1487RINReceiver Input Resistance-7V VCM 12V,all devices exceptMAX487/MAX1487R=27(RS-485),Figure 40.4V VO 2.4VR=50(RS-422)IO=4mA,VID=-200mVIO=-4mA,VID=200mVVCM=0V-7V VCM 12VDE,DI,REDE,DI,REMAX487/MAX1487,DE=0V,VCC=0V or 5.25VDE,DI,RER=27 or 50,Figure 4R=27 or 50,Figure 4R=27 or 50,Figure 4DE=0V;VCC=0V or 5.25V,all devices exceptMAX487/MAX1487CONDITIONSk12A1IOZRThree-State(high impedance)Output Current at ReceiverV0.4VOLReceiver Output Low Voltage3.5VOHReceiver Output High VoltagemV70VTHReceiver Input HysteresisV-0.20.2Receiver Differential ThresholdVoltage-0.2mA0.25mA-0.81.01.55VOD2Differential Driver Output(with load)V2V5VOD1Differential Driver Output(no load)A2IIN1Input CurrentV0.8VILInput Low VoltageV2.0VIHInput High VoltageV0.2VODChange in Magnitude of DriverCommon-Mode Output Voltagefor Complementary Output StatesV0.2VODChange in Magnitude of DriverDifferential Output Voltage forComplementary Output StatesV3VOCDriver Common-Mode OutputVoltageUNITSMINTYPMAXSYMBOLPARAMETERMAX481/MAX483/MAX485/MAX487MAX491/MAX1487Low-Power,Slew-Rate-LimitedRS-485/RS-422 Transceivers_3SWITCHING CHARACTERISTICSMAX481/MAX485,MAX490/MAX491,MAX1487(VCC=5V 5%,TA=TMINto TMAX,unless otherwise noted.)(Notes 1,2)DC ELECTRICAL CHARACTERISTICS(continued)(VCC=5V 5%,TA=TMINto TMAX,unless otherwise noted.)(Notes 1,2)mA7950V VO VCCIOSRReceiver Short-Circuit CurrentmA35250-7V VO12V(Note 4)IOSD2Driver Short-Circuit Current,VO=LowmA35250-7V VO12V(Note 4)IOSD1Driver Short-Circuit Current,VO=HighMAX1487,RE=0V or VCC250400350650ns103060tPHLDriver Rise or Fall TimeFigures 6 and 8,RDIFF=54,CL1=CL2=100pFnsMAX490M,MAX491MMAX490C/E,MAX491C/E2090150MAX481,MAX485,MAX1487MAX490M,MAX491MMAX490C/E,MAX491C/EMAX481,MAX485,MAX1487Figures 6 and 8,RDIFF=54,CL1=CL2=100pFMAX481(Note 5)Figures 5 and 11,CRL=15pF,S2 closedFigures 5 and 11,CRL=15pF,S1 closedFigures 5 and 11,CRL=15pF,S2 closedFigures 5 and 11,CRL=15pF,S1 closedFigures 6 and 10,RDIFF=54,CL1=CL2=100pFFigures 6 and 8,RDIFF=54,CL1=CL2=100pFFigures 6 and 10,RDIFF=54,CL1=CL2=100pFCONDITIONSns510tSKEWns50200600tSHDNTime to ShutdownMbps2.5fMAXMaximum Data Ratens2050tHZReceiver Disable Time from Highns103060tPLH2050tLZReceiver Disable Time from Lowns2050tZHDriver Input to OutputReceiver Enable to Output Highns2050tZLReceiver Enable to Output Low2090200nsns134070tHZtSKDDriver Disable Time from High|tPLH-tPHL|DifferentialReceiver Skewns4070tLZDriver Disable Time from Lowns4070tZLDriver Enable to Output Low31540ns51525ns31540tR,tF2090200Driver Output Skew to OutputtPLH,tPHLReceiver Input to Output4070tZHDriver Enable to Output HighUNITSMINTYPMAXSYMBOLPARAMETERCONDITIONSUNITSMINTYPMAXSYMBOLPARAMETER230400300500MAX481/MAX485,RE=0V or VCC500900MAX490/MAX491,DE,DI,RE=0V or VCC300500MAX488/MAX489,DE,DI,RE=0V or VCC120250DE=VCC300500DE=0VDE=VCCDE=0VAMAX481/483/487,DE=0V,RE=VCC0.110ISHDNSupply Current in Shutdown 120250ICCNo-Load Supply Current(Note 3)DE=5VDE=0VMAX483MAX487MAX483/MAX487,RE=0V or VCCFigures 7 and 9,CL=100pF,S2 closedFigures 7 and 9,CL=100pF,S1 closedFigures 7 and 9,CL=15pF,S1 closedFigures 7 and 9,CL=15pF,S2 closedAMAX481/MAX483/MAX485/MAX487MAX491/MAX1487Low-Power,Slew-Rate-LimitedRS-485/RS-422 Transceivers4_SWITCHING CHARACTERISTICSMAX483,MAX487/MAX488/MAX489(VCC=5V 5%,TA=TMINto TMAX,unless otherwise noted.)(Notes 1,2)SWITCHING CHARACTERISTICSMAX481/MAX485,MAX490/MAX491,MAX1487(continued)(VCC=5V 5%,TA=TMINto TMAX,unless otherwise noted.)(Notes 1,2)3001000Figures 7 and 9,CL=100pF,S2 closedFigures 7 and 9,CL=100pF,S1 closedFigures 5 and 11,CL=15pF,S2 closed,A-B=2VCONDITIONSns40100tZH(SHDN)Driver Enable from Shutdown toOutput High(MAX481)nsFigures 5 and 11,CL=15pF,S1 closed,B-A=2VtZL(SHDN)Receiver Enable from Shutdownto Output Low(MAX481)ns40100tZL(SHDN)Driver Enable from Shutdown toOutput Low(MAX481)ns3001000tZH(SHDN)Receiver Enable from Shutdownto Output High(MAX481)UNITSMINTYPMAXSYMBOLPARAMETERtPLHtSKEWFigures 6 and 8,RDIFF=54,CL1=CL2=100pFtPHLFigures 6 and 8,RDIFF=54,CL1=CL2=100pFDriver Input to OutputDriver Output Skew to Outputns100800nsns2000MAX483/MAX487,Figures 7 and 9,CL=100pF,S2 closedtZH(SHDN)Driver Enable from Shutdown toOutput High 2502000ns2500MAX483/MAX487,Figures 5 and 11,CL=15pF,S1 closedtZL(SHDN)Receiver Enable from Shutdownto Output Low ns2500MAX483/MAX487,Figures 5 and 11,CL=15pF,S2 closedtZH(SHDN)Receiver Enable from Shutdownto Output High ns2000MAX483/MAX487,Figures 7 and 9,CL=100pF,S1 closedtZL(SHDN)Driver Enable from Shutdown toOutput Low ns50200600MAX483/MAX487(Note 5)tSHDNTime to Shutdown tPHLtPLH,tPHL B by 200mV,RO will be high;If A +0.2V?-0.2V?Inputs open?X1?0?1?High-Z*X=Dont care?High-Z=High impedance?*Shutdown mode for MAX481/MAX483/MAX487INPUTSOUTPUTSREDEDIZYX?X?0?11?1?0?01?0?X?X0?1?High-Z?High-Z*1?0?High-Z?High-Z*X=Dont care?High-Z=High impedance?*Shutdown mode for MAX481/MAX483/MAX487Low-Power Shutdown Mode(MAX481/MAX483/MAX487)A low-power shutdown mode is initiated by bringingboth REhigh and DE low.The devices will not shutdown unless both the driver and receiver are disabled.In shutdown,the devices typically draw only 0.1A ofsupply current.REand DE may be driven simultaneously;the parts areguaranteed not to enter shutdown if REis high and DEis low for less than 50ns.If the inputs are in this statefor at least 600ns,the parts are guaranteed to entershutdown.For the MAX481,MAX483,and MAX487,the tZHandtZLenable times assume the part was not in the low-power shutdown state(the MAX485/MAX488MAX491and MAX1487 can not be shut down).The tZH(SHDN)and tZL(SHDN)enable times assume the parts were shutdown(see Electrical Characteristics).It takes the drivers and receivers longer to becomeenabled from the low-power shutdown state(tZH(SHDN),tZL(SHDN)than from the operating mode(tZH,tZL).(The parts are in operating mode if the RE,DE inputs equal a logical 0,1 or 1,1 or 0,0.)Driver Output Protection Excessive output current and power dissipation causedby faults or by bus contention are prevented by twomechanisms.A foldback current limit on the outputstage provides immediate protection against short cir-cuits over the whole common-mode voltage range(seeTypical Operating Characteristics).In addition,a ther-mal shutdown circuit forces the driver outputs into ahigh-impedance state if the die temperature risesexcessively.Propagation DelayMany digital encoding schemes depend on the differ-ence between the driver and receiver propagationdelay times.Typical propagation delays are shown inFigures 1518 using Figure 14s test circuit.The difference in receiver delay times,|tPLH-tPHL|,istypically under 13ns for the MAX481,MAX485,MAX490,MAX491,and MAX1487 and is typically lessthan 100ns for the MAX483 and MAX487MAX489.The driver skew times are typically 5ns(10ns max)forthe MAX481,MAX485,MAX490,MAX491,andMAX1487,and are typically 100ns(800ns max)for theMAX483 and MAX487MAX489.MAX481/MAX483/MAX485/MAX487MAX491/MAX1487Low-Power,Slew-Rate-LimitedRS-485/RS-422 Transceivers_1110dB/div0Hz5MHz500kHz/div10dB/div0Hz5MHz500kHz/divFigure 12.Driver Output Waveform and FFT Plot of MAX481/MAX485/MAX490/MAX491/MAX1487 Transmitting a 150kHzSignalFigure 13.Driver Output Waveform and FFT Plot of MAX483/MAX487MAX489 Transmitting a 150kHz SignalMAX481/MAX483/MAX485/MAX487MAX491/MAX1487Low-Power,Slew-Rate-LimitedRS-485/RS-422 Transceivers12_TTL IN?tR,tF 6nsDR100pFB100pFARECEIVER?OUTR=54ZY500mV/div20ns/divABRO2V/divVCC=5V?TA=+25C500mV/div20ns/divABRO2V/divVCC=5V?TA=+25C500mV/div400ns/divABRO2V/divVCC=5V?TA=+25C500mV/div400ns/divABRO2V/divVCC=5V?TA=+25CFigure 14.Receiver Propagation Delay Test CircuitFigure 15.MAX481/MAX485/MAX490/MAX491/MAX1487Receiver tPHLFigure 16.MAX481/MAX485/MAX490/MAX491/MAX1487Receiver tPLHFigure 17.MAX483,MAX487MAX489 Receiver tPHLFigure 18.MAX483,MAX487MAX489 Receiver tPLHLine Length vs.Data RateThe RS-485/RS-422 standard covers line lengths up to4000 feet.For line lengths greater than 4000 feet,seeFigure 23.Figures 19 and 20 show the system differential voltagefor the parts driving 4000 feet of 26AWG twisted-pairwire at 110kHz into 120 loads.Typical ApplicationsThe MAX481,MAX483,MAX485,MAX487MAX491,andMAX1487 transceivers are designed for bidirectional datacommunications on multipoint bus transmission lines.Figures 21 and 22 show typical network applicationscircuits.These parts can also be used as linerepeaters,with cable lengths longer than 4000 feet,asshown in Figure 23.To minimize reflections,the line should be terminated atboth ends in its characteristic impedance,and stublengths off the main line should be kept as short as possi-ble.The slew-rate-limited MAX483 and MAX487MAX489are more tolerant of imperfect termination.MAX481/MAX483/MAX485/MAX487MAX491/MAX1487Low-Power,Slew-Rate-LimitedRS-485/RS-422 Transceivers_13DIVY-VZRO5V0V1V0V-1V5V0V2s/divDIVY-VZRO5V0V1V0V-1V5V0V2s/divDIRODEREABRERERERORORODIDIDIDEDEDEDDDRRRBBBAAA120120DRMAX481?MAX483?MAX485?MAX487?MAX1487Figure 19.MAX481/MAX485/MAX490/MAX491/MAX1487System Differential Voltage at 110kHz Driving 4000ft of CableFigure 20.MAX483,MAX487MAX489 System DifferentialVoltage at 110kHz Driving 4000ft of CableFigure 21.MAX481/MAX483/MAX485/MAX487/MAX1487 Typical Half-Duplex RS-485 NetworkMAX481/MAX483/MAX485/MAX487MAX491/MAX1487Low-Power,Slew-Rate-LimitedRS-485/RS-422 Transceivers14_Figure 22.MAX488MAX491 Full-Duplex RS-485 Network120120RDROREDEDIABY120120DIDIDIRORORODEDEDEREREREZZZZYYYAAABBBDDDRRRMAX488?MAX489?MAX490?MAX491NOTE:RE AND DE ON MAX489/MAX491 ONLY.Figure 23.Line Repeater for MAX488MAX491120120DATA INDATA OUTRDROREDEDIABZYMAX488MAX491NOTE:RE AND DE ON MAX489/MAX491 ONLY.Isolated RS-485For isolated RS-485 applications,see the MAX253 andMAX1480 data sheets.MAX481/MAX483/MAX485/MAX487MAX491/MAX1487Low-Power,Slew-Rate-LimitedRS-485/RS-422 Transceivers_15_Ordering Information(continued)_Chip TopographiesMAX481/MAX483/MAX485/MAX487/MAX1487N.C.RO0.054?(1.372mm)0.080?(2.032mm)DE DIGNDBN.C.VCCA RE*Contact factory for dice specifications.14 CERDIP-55C to+125CMAX489MJD14 SO-40C to+85CMAX489ESD14 Plastic DIP-40C to+85CMAX489EPDDice*0C to+70CMAX489C/D14 SO0C to+70CMAX489CSD14 Plastic DIP0C to+70CMAX489CPD8 CERDIP-55C to+125CMAX488MJA8 SO-40C to+85CMAX488ESA8 Plastic DIP-40C to+85CMAX488EPADice*0C to+70CMAX488C/D8 SO0C to+70CMAX488CSA8 Plastic DIP0C to+70CMAX488CPA8 CERDIP-55C to+125CMAX487MJA8 SO-40C to+85CMAX487ESA8 Plastic DIP-40C to+85CMAX487EPADice*0C to+70CMAX487C/D8 SO0C to+70CMAX487CSA8 Plastic DIP0C to+70CMAX487CPA8 CERDIP-55C to+125CMAX485MJA8 SO-40C to+85CMAX485ESA8 Plastic DIP-40C to+85CMAX485EPADice*0C to+70CM