MEMORY存储芯片MAX485EESA中文规格书

±15kV ESD-Protected, Slew-Rate-Limited,

Low-Power, RS-485/RS-422 TransceiversGeneral DescriptionThe MAX481E, MAX483E, MAX485E, MAX487E–MAX491E, and MAX1487E are low-power transceivers forRS-485 and RS-422 communications in harsh environ-ments. Each driver output and receiver input is protectedagainst ±15kV electro-static discharge (ESD) shocks,without latchup. These parts contain one driver and onereceiver. The MAX483E, MAX487E, MAX488E, andMAX489E feature reduced slew-rate drivers that minimizeEMI and reduce reflections caused by improperly termi-nated cables, thus allowing error-free data transmissionup to 250kbps. The driver slew rates of the MAX481E,MAX485E, MAX490E, MAX491E, and MAX1487E are notlimited, allowing them to transmit up to transceivers draw as little as 120µA supply cur-rent when unloaded or when fully loaded with disableddrivers (see Selector Guide). Additionally, the MAX481E,MAX483E, and MAX487E have a low-current shutdownmode in which they consume only 0.5µA. All parts oper-ate from a single +5V s are short-circuit current limited, and are protectedagainst excessive power dissipation by thermal shutdowncircuitry that places their outputs into a high-impedancestate. The receiver input has a fail-safe feature that guar-antees a logic-high output if the input is open MAX487E and MAX1487E feature quarter-unit-loadreceiver input impedance, allowing up to 128 trans-ceivers on the bus. The MAX488E–MAX491E aredesigned for full-duplex communications, while theMAX481E, MAX483E, MAX485E, MAX487E, andMAX1487E are designed for half-duplex applications that are not ESD sensitive see the pin-and function-compatible MAX481, MAX483, MAX485,MAX487–MAX491, and ationsLow-Power RS-485 TransceiversLow-Power RS-422 TransceiversLevel TranslatorsTransceivers for EMI-Sensitive ApplicationsIndustrial-Control Local Area NetworksNext-Generation Device Features♦For Fault-Tolerant Applications:MAX3430: ±80V Fault-Protected, Fail-Safe, 1/4-Unit Load, +3.3V, RS-485 TransceiverMAX3080–MAX3089: Fail-Safe, High-Speed(10Mbps), Slew-Rate-Limited, RS-485/RS-422Transceivers♦For Space-Constrained Applications:MAX3460–MAX3464: +5V, Fail-Safe, 20Mbps,Profibus, RS-485/RS-422 TransceiversMAX3362: +3.3V, High-Speed, RS-485/RS-422Transceiver in a SOT23 PackageMAX3280E–MAX3284E: ±15kV ESD-Protected,52Mbps, +3V to +5.5V, SOT23, RS-485/RS-422True Fail-Safe ReceiversMAX3030E–MAX3033E: ±15kV ESD-Protected,+3.3V, Quad RS-422 Transmitters♦For Multiple Transceiver Applications:MAX3293/MAX3294/MAX3295: 20Mbps, +3.3V,SOT23, RS-485/RS-422 Transmitters♦For Fail-Safe Applications:MAX3440E–MAX3444E: ±15kV ESD-Protected,±60V Fault-Protected, 10Mbps, Fail-SafeRS-485/J1708 Transceivers♦For Low-Voltage Applications:MAX3483E/MAX3485E/MAX3486E/MAX3488E/MAX3490E/MAX3491E: +3.3V Powered, ±15kVESD-Protected, 12Mbps, Slew-Rate-Limited,True RS-485/RS-422 TransceiversOrdering InformationPARTTEMP RANGEPIN-PACKAGEMAX481ECPA0°C to +70°C8 Plastic DIPMAX481ECSA0°C to +70°C8 SOMAX481EEPA-40°C to +85°C8 Plastic DIPMAX481EESA-40°C to +85°C8 SOMAX483ECPA0°C to +70°C8 Plastic DIPMAX483ECSA0°C to +70°C8 SOMAX483EEPA-40°C to +85°C8 Plastic DIPMAX483EESA-40°C to +85°C8 SOOrdering Information continued at end of data or Guide appears at end of data sheet.

MAX481E/MAX483E/MAX485E/

MAX487E–MAX491E/MAX1487E±15kV ESD-Protected, Slew-Rate-Limited,Low-Power, RS-485/RS-422 Transceivers__________Function Tables

(MAX481E/MAX483E/MAX485E/MAX487E/MAX1487E)Table 1. TransmittingINPUTSOUTPUTSREDEDIZYX1101X101000XHigh-ZHigh-Z10XHigh-Z*High-Z*X = Don't careHigh-Z = High impedance*Shutdown mode for MAX481E/MAX483E/MAX487E__________Applications InformationThe MAX481E/MAX483E/MAX485E/MAX487E–MAX491E

and MAX1487E are low-power transceivers for RS-485

and RS-422 communications. These “E” versions of the

MAX481, MAX483, MAX485, MAX487–MAX491, and

MAX1487 provide extra protection against ESD. Therugged MAX481E, MAX483E, MAX485E, MAX497E–MAX491E, and MAX1487E are intended for harsh envi-ronments where high-speed communication is important.

These devices eliminate the need for transient suppres-sor diodes and the associated high capacitance standard (non-“E”) MAX481, MAX483, MAX485,

MAX487–MAX491, and MAX1487 are recommended for

applications where cost is MAX481E, MAX485E, MAX490E, MAX491E, and

MAX1487E can transmit and receive at data rates up to

2.5Mbps, while the MAX483E, MAX487E, MAX488E,

and MAX489E are specified for data rates up to

250kbps. The MAX488E–MAX491E are full-duplex

transceivers, while the MAX481E, MAX483E, MAX487E,

and MAX1487E are half-duplex. In addition, driver-enable (DE) and receiver-enable (RE) pins are included

on the MAX481E, MAX483E, MAX485E, MAX487E,

MAX489E, MAX491E, and MAX1487E. When disabled,

the driver and receiver outputs are high impedance.±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 have

extra protection against static electricity. Maxim’s engi-Table 2. ReceivingINPUTSOUTPUTREDEA-BRO00>+0.2V100< -0.2V000Inputs open110XHigh-Z*X = Don't careHigh-Z = High impedance*Shutdown mode for MAX481E/MAX483E/MAX487Eneers developed state-of-the-art structures to protectthese pins against ESD of ±15kV without damage. TheESD structures withstand high ESD in all states: normaloperation, shutdown, and powered down. After an ESDevent, Maxim’s MAX481E, MAX483E, MAX485E,

MAX487E–MAX491E, and MAX1487E keep workingwithout protection can be tested in various ways; thetransmitter outputs and receiver inputs of this productfamily are characterized for protection to ±15kV usingthe Human Body ESD test methodologies include IEC10004-2 con-tact discharge and IEC1000-4-2 air-gap discharge (for-merly IEC801-2).ESD Test ConditionsESD performance depends on a variety of t Maxim for a reliability report that documentstest set-up, test methodology, and test Body ModelFigure 4 shows the Human Body Model, and Figure 5shows the current waveform it generates when dis-charged into a low impedance. This model consists ofa 100pF capacitor charged to the ESD voltage of inter-est, which is then discharged into the test devicethrough a 1.5kΩ1000-4-2The IEC1000-4-2 standard covers ESD testing and per-formance of finished equipment; it does not specificallyrefer to integrated circuits (Figure 6).

MAX481E/MAX483E/MAX485E/

MAX487E–MAX491E/MAX1487E±15kV ESD-Protected, Slew-Rate-Limited,Low-Power, RS-485/RS-422 TransceiversRC 1MRD 1500ΩCHARGE CURRENTDISCHARGELIMIT RESISTORRESISTANCEHIGHVOLTAGECSTORAGEDEVICEDC100pFsCAPACITORUNDERTESTSOURCEFigure 4. Human Body ESD Test ModelRC 50M to 100MRD 330ΩCHARGE CURRENTDISCHARGELIMIT RESISTORRESISTANCEHIGH-CSTORAGEDEVICEVOLTAGE150pFsCAPACITORUNDERDCTESTSOURCEFigure 6. IEC1000-4-2 ESD Test ModelYRVODRVOCZFigure 8. Driver DC Test LoadIP 100%I90%rPEAK-TO-PEAK RINGING(NOT DRAWN TO SCALE)AMPERES36.8%10%00tRLTIMEtDLCURRENT WAVEFORMFigure 5. Human Body Model Current WaveformI100%90%KAEPI10%tr = 0.7ns to 1nst30ns60nsFigure 7. IEC1000-4-2 ESD Generator Current WaveformRECEIVERTEST POINT1kOUTPUTVCS1CCRL15pF1kS2Figure 9. Receiver Timing Test Load

MAX481E/MAX483E/MAX485E/

MAX487E–MAX491E/MAX1487E

MAX481E/MAX483E/MAX485E/

MAX487E–MAX491E/MAX1487E±15kV ESD-Protected, Slew-Rate-Limited,Low-Power, RS-485/RS-422 Transceivers100pFZBTTL INtR, tF < 6nsDRRECEIVEROUTYR = 54ΩA100pFFigure 18. Receiver Propagation Delay Test CircuitIt takes the drivers and receivers longer to become

enabled 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 caused

by faults or by bus contention are prevented by two

mechanisms. A foldback current limit on the output stage

provides immediate protection against short circuits over

the whole common-mode voltage range (see

Typical

Operating Characteristics). In addition, a thermal shut-down circuit forces the driver outputs into a high-imped-ance state if the die temperature rises ation Delay

Many digital encoding schemes depend on the differ-delay times. Typical propagation delays are shown inFigures 19–22 using Figure 18’s test difference in receiver delay times, tPLH- tPHL, istypically under 13ns for the MAX481E, MAX485E,MAX490E, MAX491E, and MAX1487E, and is typicallyless than 100ns for the MAX483E and MAX487E– driver skew times are typically 5ns (10ns max) forthe MAX481E, MAX485E, MAX490E, MAX491E, andMAX1487E, and are typically 100ns (800ns max) for theMAX483E and MAX487E–l ApplicationsThe MAX481E, MAX483E, MAX485E, MAX487E–MAX491E, and MAX1487E transceivers are designed forbidirectional data communications on multipoint bustransmission lines. Figures 25 and 26 show typical net-work application circuits. These parts can also be used asline repeaters, with cable lengths longer than 4000 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 MAX483E and MAX487E–MAX489E are more tolerant of imperfect the VCCpin with 0.1µed RS-485For isolated RS-485 applications, see the MAX253 andMAX1480 data Length vs. Data RateThe RS-485/RS-422 standard covers line lengths up to4000 feet. Figures 23 and 24 show the system differen-tial voltage for the parts driving 4000 feet of 26AWGtwisted-pair wire at 110kHz into 100Ωloads.