MAX485中文资料[1]

本文是 Maxim正式英文资料的译文，Maxim不对翻译中存在的差异或由此产生的错误负责。请注意译文中可能存在文字组织或 翻译错误，如需确认任何词语的准确性，请参考Maxim提供的英文版资料。 索取免费样品和最新版的数据资料，请访问 Maxim的主页：www.maxim-ic.com.cn。 _______________________________ 概述 MAX481、MAX483、MAX485、MAX487-MAX491以及 MAX1487是用于RS-485与RS-422通信的低功耗收发器， 每个器件中都具有一个驱动器和一个接收器。MAX483、 MAX487、MAX488以及MAX489具有限摆率驱动器，可 以减小EMI，并降低由不恰当的终端匹配电缆引起的反射， 实现最高 2 5 0 k b p s的无差错数据传输。M A X 4 8 1、 MAX485、MAX490、MAX491、MAX1487的驱动器摆 率不受限制，可以实现最高2.5Mbps的传输速率。 这些收发器在驱动器禁用的空载或满载状态下，吸取的 电源电流在 120(A至 500(A之间。另外，MAX481、 MAX483与MAX487具有低电流关断模式，仅消耗 0.1µA。所有器件都工作在5V单电源下。 驱动器具有短路电流限制，并可以通过热关断电路将驱 动器输出置为高阻状态，防止过度的功率损耗。接收器 输入具有失效保护特性，当输入开路时，可以确保逻辑 高电平输出。 MAX487与MAX1487具有四分之一单位负载的接收器输 入阻抗，使得总线上最多可以有 1 2 8个M A X 4 8 7 / MAX1487收发器。使用MAX488-MAX491可以实现全双 工通信，而MAX481、MAX483、MAX485、MAX487与 MAX1487则为半双工应用设计。 _______________________________ 应用 低功耗RS-485收发器 低功耗RS-422收发器 电平转换器 用于EMI敏感应用的收发器 工业控制局域网 ____________________ 下一代器件的特性 ♦ 容错应用 MAX3430: ±80V故障保护、失效保护、1/4单位 负载、+3.3V、RS-485收发器 MAX3440E-MAX3444E: ±15kV ESD保护、±60V 故障保护、10Mbps、失效保护、 RS-485/J1708收发器 ♦ 对于空间受限应用 MAX3460-MAX3464: +5V、失效保护、20Mbps、 Profibus RS-485/RS-422收发器 MAX3362: +3.3V、高速、RS-485/RS-422收发器， 采用SOT23封装 MAX3280E-MAX3284E: ±15kV ESD保护、 52Mbps、+3V至+5.5V、SOT23、 RS-485/RS-422、真失效保护接收器 MAX3293/MAX3294/MAX3295: 20Mbps、+3.3V、 SOT23、RS-485/RS-422发送器 ♦ 对于多通道收发器应用 MAX3030E-MAX3033E: ±15kV ESD保护、 +3.3V、四路RS-422发送器 ♦ 对于失效保护应用 MAX3080-MAX3089: 失效保护、高速(10Mbps)、 限摆率RS-485/RS-422收发器 ♦ 对于低电压应用 MAX3483E/MAX3485E/MAX3486E/MAX3488E/ MAX3490E/MAX3491E: +3.3V供电、±15kV ESD 保护、12Mbps、限摆率、真正的RS-485/RS-422 收发器 M A X 4 8 1 /M A X 4 8 3 /M A X 4 8 5 /M A X 4 8 7 –M A X 4 9 1 /M A X 1 4 8 7 低功耗、限摆率、 RS-485/RS-422收发器 ________________________________________________________________ Maxim Integrated Products 1 _____________________________________________________________________ 选择表 19-0122; Rev 8; 10/03 MAX481 MAX483 MAX485 MAX487 MAX488 MAX489 MAX490 MAX491 MAX1487 PART NUMBER HALF/FULL DUPLEX DATA RATE (Mbps) SLEW-RATE LIMITED LOW-POWER SHUTDOWN RECEIVER/ DRIVER ENABLE QUIESCENT CURRENT (µA) NUMBER OF TRANSMITTERS ON BUS PIN COUNT Half Half Half Half Full Full Full Full Half 2.5 0.25 2.5 0.25 0.25 0.25 2.5 2.5 2.5 No Yes No Yes Yes Yes No No No Yes Yes No Yes No No No No No Yes Yes Yes Yes No Yes No Yes Yes 300 120 300 120 120 120 300 300 230 32 32 32 128 32 32 32 32 128 8 8 8 8 8 14 8 14 8 定购信息在本资料的最后给出。 海纳电子资讯网： www.fpga-arm.com M A X 4 8 1 /M A X 4 8 3 /M A X 4 8 5 /M A X 4 8 7 –M A X 4 9 1 /M A X 1 4 8 7 低功耗、限摆率、 RS-485/RS-422收发器 2 _______________________________________________________________________________________ ABSOLUTE MAXIMUM RATINGS Supply Voltage (VCC).............................................................12V Control 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 +12.5V Receiver Input Voltage (A, B).................................-8V to +12.5V Receiver Output Voltage (RO).....................-0.5V to (VCC +0.5V) Continuous Power Dissipation (TA = +70°C) 8-Pin Plastic DIP (derate 9.09mW/°C above +70°C) ....727mW 14-Pin Plastic DIP (derate 10.00mW/°C above +70°C) ..800mW 8-Pin SO (derate 5.88mW/°C above +70°C).................471mW 14-Pin SO (derate 8.33mW/°C above +70°C)...............667mW 8-Pin µMAX (derate 4.1mW/°C above +70°C) ..............830mW 8-Pin CERDIP (derate 8.00mW/°C above +70°C).........640mW 14-Pin CERDIP (derate 9.09mW/°C above +70°C).......727mW Operating Temperature Ranges MAX4_ _C_ _/MAX1487C_ A ...............................0°C to +70°C MAX4_ _E_ _/MAX1487E_ A.............................-40°C to +85°C MAX4_ _MJ_/MAX1487MJA ...........................-55°C to +125°C Storage Temperature Range .............................-65°C to +160°C Lead Temperature (soldering, 10sec) .............................+300°C DC ELECTRICAL CHARACTERISTICS (VCC = 5V ±5%, TA = TMIN to 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 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 absolute maximum rating conditions for extended periods may affect device reliability. V VIN = -7V VIN = 12V VIN = -7V VIN = 12V Input Current (A, B) IIN2 VTH kΩ48-7V ≤ VCM ≤ 12V, MAX487/MAX1487 RINReceiver Input Resistance -7V ≤ VCM ≤ 12V, all devices except MAX487/MAX1487 R = 27Ω (RS-485), Figure 4 0.4V ≤ VO ≤ 2.4V R = 50Ω (RS-422) IO = 4mA, VID = -200mV IO = -4mA, VID = 200mV VCM = 0V -7V ≤ VCM ≤ 12V DE, DI, RE DE, DI, RE MAX487/MAX1487, DE = 0V, VCC = 0V or 5.25V DE, DI, RE R = 27Ω or 50Ω, Figure 4 R = 27Ω or 50Ω, Figure 4 R = 27Ω or 50Ω, Figure 4 DE = 0V; VCC = 0V or 5.25V, all devices except MAX487/MAX1487 CONDITIONS kΩ12 µA±1IOZR Three-State (high impedance) Output Current at Receiver V 0.4VOLReceiver Output Low Voltage 3.5VOHReceiver Output High Voltage mV70∆VTHReceiver Input Hysteresis V-0.2 0.2 Receiver Differential Threshold Voltage -0.2 mA 0.25 mA -0.8 1.0 1.5 5 VOD2 Differential Driver Output (with load) V 2 V5VOD1Differential Driver Output (no load) µA±2IIN1Input Current V0.8VILInput Low Voltage V2.0VIHInput High Voltage V0.2∆VOD Change in Magnitude of Driver Common-Mode Output Voltage for Complementary Output States V0.2∆VOD Change in Magnitude of Driver Differential Output Voltage for Complementary Output States V3VOC Driver Common-Mode Output Voltage UNITSMIN TYP MAXSYMBOLPARAMETER 海纳电子资讯网： www.fpga-arm.com M A X 4 8 1 /M A X 4 8 3 /M A X 4 8 5 /M A X 4 8 7 –M A X 4 9 1 /M A X 1 4 8 7 低功耗、限摆率、 RS-485/RS-422收发器 _______________________________________________________________________________________ 3 SWITCHING CHARACTERISTICS—MAX481/MAX485, MAX490/MAX491, MAX1487 (VCC = 5V ±5%, TA = TMIN to TMAX, unless otherwise noted.) (Notes 1, 2) DC ELECTRICAL CHARACTERISTICS (continued) (VCC = 5V ±5%, TA = TMIN to TMAX, unless otherwise noted.) (Notes 1, 2) mA7 950V ≤ VO ≤ VCCIOSRReceiver Short-Circuit Current mA35 250-7V ≤ VO ≤12V (Note 4)IOSD2 Driver Short-Circuit Current, VO = Low mA35 250-7V ≤ VO ≤12V (Note 4)IOSD1 Driver Short-Circuit Current, VO = High MAX1487, RE = 0V or VCC 250 400 350 650 ns 10 30 60tPHL Driver Rise or Fall Time Figures 6 and 8, RDIFF = 54Ω, CL1 = CL2 = 100pF ns MAX490M, MAX491M MAX490C/E, MAX491C/E 20 90 150 MAX481, MAX485, MAX1487 MAX490M, MAX491M MAX490C/E, MAX491C/E MAX481, MAX485, MAX1487 Figures 6 and 8, RDIFF = 54Ω, CL1 = CL2 = 100pF MAX481 (Note 5) Figures 5 and 11, CRL = 15pF, S2 closed Figures 5 and 11, CRL = 15pF, S1 closed Figures 5 and 11, CRL = 15pF, S2 closed Figures 5 and 11, CRL = 15pF, S1 closed Figures 6 and 10, RDIFF = 54Ω, CL1 = CL2 = 100pF Figures 6 and 8, RDIFF = 54Ω, CL1 = CL2 = 100pF Figures 6 and 10, RDIFF = 54Ω, CL1 = CL2 = 100pF CONDITIONS ns 5 10tSKEW ns50 200 600tSHDNTime to Shutdown Mbps2.5fMAXMaximum Data Rate ns20 50tHZReceiver Disable Time from High ns 10 30 60tPLH 20 50tLZReceiver Disable Time from Low ns20 50tZH Driver Input to Output Receiver Enable to Output High ns20 50tZLReceiver Enable to Output Low 20 90 200 ns ns 13 40 70tHZ tSKD Driver Disable Time from High | tPLH - tPHL | Differential Receiver Skew ns40 70tLZDriver Disable Time from Low ns 40 70tZLDriver Enable to Output Low 3 15 40 ns 5 15 25 ns 3 15 40 tR, tF 20 90 200 Driver Output Skew to Output tPLH, tPHLReceiver Input to Output 40 70tZHDriver Enable to Output High UNITSMIN TYP MAXSYMBOLPARAMETER CONDITIONS UNITSMIN TYP MAXSYMBOLPARAMETER 230 400 300 500 MAX481/MAX485, RE = 0V or VCC 500 900 MAX490/MAX491, DE, DI, RE = 0V or VCC 300 500 MAX488/MAX489, DE, DI, RE = 0V or VCC 120 250 DE = VCC 300 500DE = 0V DE = VCC DE = 0V µAMAX481/483/487, DE = 0V, RE = VCC 0.1 10ISHDNSupply Current in Shutdown 120 250 ICC No-Load Supply Current (Note 3) DE = 5V DE = 0V MAX483 MAX487 MAX483/MAX487, RE = 0V or VCC Figures 7 and 9, CL = 100pF, S2 closed Figures 7 and 9, CL = 100pF, S1 closed Figures 7 and 9, CL = 15pF, S1 closed Figures 7 and 9, CL = 15pF, S2 closed µA 海纳电子资讯网： www.fpga-arm.com M A X 4 8 1 /M A X 4 8 3 /M A X 4 8 5 /M A X 4 8 7 –M A X 4 9 1 /M A X 1 4 8 7 低功耗、限摆率、 RS-485/RS-422收发器 4 _______________________________________________________________________________________ SWITCHING CHARACTERISTICS—MAX483, MAX487/MAX488/MAX489 (VCC = 5V ±5%, TA = TMIN to TMAX, unless otherwise noted.) (Notes 1, 2) SWITCHING CHARACTERISTICS—MAX481/MAX485, MAX490/MAX491, MAX1487 (continued) (VCC = 5V ±5%, TA = TMIN to TMAX, unless otherwise noted.) (Notes 1, 2) 300 1000 Figures 7 and 9, CL = 100pF, S2 closed Figures 7 and 9, CL = 100pF, S1 closed Figures 5 and 11, CL = 15pF, S2 closed, A - B = 2V CONDITIONS ns40 100tZH(SHDN) Driver Enable from Shutdown to Output High (MAX481) ns Figures 5 and 11, CL = 15pF, S1 closed, B - A = 2V tZL(SHDN) Receiver Enable from Shutdown to Output Low (MAX481) ns40 100tZL(SHDN) Driver Enable from Shutdown to Output Low (MAX481) ns300 1000tZH(SHDN) Receiver Enable from Shutdown to Output High (MAX481) UNITSMIN TYP MAXSYMBOLPARAMETER tPLH tSKEW Figures 6 and 8, RDIFF = 54Ω, CL1 = CL2 = 100pF tPHL Figures 6 and 8, RDIFF = 54Ω, CL1 = CL2 = 100pF Driver Input to Output Driver Output Skew to Output ns100 800 ns ns2000 MAX483/MAX487, Figures 7 and 9, CL = 100pF, S2 closed tZH(SHDN) Driver Enable from Shutdown to Output High 250 2000 ns2500 MAX483/MAX487, Figures 5 and 11, CL = 15pF, S1 closed tZL(SHDN) Receiver Enable from Shutdown to Output Low ns2500 MAX483/MAX487, Figures 5 and 11, CL = 15pF, S2 closed tZH(SHDN) Receiver Enable from Shutdown to Output High ns2000 MAX483/MAX487, Figures 7 and 9, CL = 100pF, S1 closed tZL(SHDN) Driver Enable from Shutdown to Output Low ns50 200 600MAX483/MAX487 (Note 5) tSHDNTime to Shutdown tPHL tPLH, tPHL < 50% of data period Figures 5 and 11, CRL = 15pF, S2 closed Figures 5 and 11, CRL = 15pF, S1 closed Figures 5 and 11, CRL = 15pF, S2 closed Figures 5 and 11, CRL = 15pF, S1 closed Figures 7 and 9, CL = 15pF, S2 closed Figures 6 and 10, RDIFF = 54Ω, CL1 = CL2 = 100pF Figures 7 and 9, CL = 15pF, S1 closed Figures 7 and 9, CL = 100pF, S1 closed Figures 7 and 9, CL = 100pF, S2 closed CONDITIONS kbps250fMAX 250 800 2000 Maximum Data Rate ns20 50tHZReceiver Disable Time from High ns 250 800 2000 20 50tLZReceiver Disable Time from Low ns20 50tZHReceiver Enable to Output High ns20 50tZLReceiver Enable to Output Low ns ns 100 300 3000tHZ tSKD Driver Disable Time from High I tPLH - tPHL I Differential Receiver Skew Figures 6 and 10, RDIFF = 54Ω, CL1 = CL2 = 100pF ns300 3000tLZDriver Disable Time from Low ns250 2000tZLDriver Enable to Output Low ns Figures 6 and 8, RDIFF = 54Ω, CL1 = CL2 = 100pF ns250 2000tR, tF 250 2000 Driver Rise or Fall Time ns tPLH Receiver Input to Output 250 2000tZHDriver Enable to Output High UNITSMIN TYP MAXSYMBOLPARAMETER 海纳电子资讯网： www.fpga-arm.com M A X 4 8 1 /M A X 4 8 3 /M A X 4 8 5 /M A X 4 8 7 –M A X 4 9 1 /M A X 1 4 8 7 低功耗、限摆率、 RS-485/RS-422收发器 _______________________________________________________________________________________ 5 30 0 0 2.5 OUTPUT CURRENT vs. RECEIVER OUTPUT LOW VOLTAGE 5 25 M AX 48 1- 01 OUTPUT LOW VOLTAGE (V) OU TP UT C UR RE NT (m A) 1.5 15 10 0.5 1.0 2.0 20 35 40 45 0.9 0.1 -50 -25 25 75 RECEIVER OUTPUT LOW VOLTAGE vs. TEMPERATURE 0.3 0.7 TEMPERATURE (°C) OU TP UT L OW V OL TA GE (V ) 0 50 0.5 0.8 0.2 0.6 0.4 0 100 125 M AX 48 1- 04 IRO = 8mA -20 -4 1.5 2.0 3.0 5.0 OUTPUT CURRENT vs. RECEIVER OUTPUT HIGH VOLTAGE -8 -16 M AX 48 1- 02 OUTPUT HIGH VOLTAGE (V) OU TP UT C UR RE NT (m A) 2.5 4.0 -12 -18 -6 -14 -10 -2 0 3.5 4.5 4.8 3.2 -50 -25 25 75 RECEIVER OUTPUT HIGH VOLTAGE vs. TEMPERATURE 3.6 4.4 TEMPERATURE (°C) OU TP UT H IG H VO LT AG E (V ) 0 50 4.0 4.6 3.4 4.2 3.8 3.0 100 125 M AX 48 1- 03 IRO = 8mA 90 0 0 1.0 3.0 4.5 DRIVER OUTPUT CURRENT vs. DIFFERENTIAL OUTPUT VOLTAGE 10 70 M AX 48 1- 05 DIFFERENTIAL OUTPUT VOLTAGE (V) OU TP UT C UR RE NT (m A) 2.0 4.0 50 30 80 60 40 20 0.5 1.5 2.5 3.5 2.3 1.5 -50 -25 25 125 DRIVER DIFFERENTIAL OUTPUT VOLTAGE vs. TEMPERATURE 1.7 2.1 M AX 48 1- 06 TEMPERATURE (°C) DI FF ER EN TI AL O UT PU T VO LT AG E (V ) 0 75 1.9 2.2 1.6 2.0 1.8 10050 2.4 R = 54Ω _______________________________________________________________ 典型工作特性 (VCC = 5V, TA = +25°C, unless otherwise noted.) NOTES FOR ELECTRICAL/SWITCHING CHARACTERISTICS Note 1: All currents into device pins are positive; all currents out of device pins are negative. All voltages are referenced to device ground unless otherwise specified. Note 2: All typical specifications are given for VCC = 5V and TA = +25°C. Note 3: Supply current specification is valid for loaded transmitters when DE = 0V. Note 4: Applies to peak current. See Typical Operating Characteristics. Note 5: The MAX481/MAX483/MAX487 are put into shutdown by bringing RE high and DE low. If the inputs are in this state for less than 50ns, the parts are guaranteed not to enter shutdown. If the inputs are in this state for at least 600ns, the parts are guaranteed to have entered shutdown. See Low-Power Shutdown Mode section. 海纳电子资讯网： www.fpga-arm.com M A X 4 8 1 /M A X 4 8 3 /M A X 4 8 5 /M A X 4 8 7 –M A X 4 9 1 /M A X 1 4 8 7 低功耗、限摆率、 RS-485/RS-422收发器 6 _______________________________________________________________________________________ __________________________________________________________ 典型工作特性（续） (VCC = 5V, TA = +25°C, unless otherwise noted.) 120 0 0 8 OUTPUT CURRENT vs. DRIVER OUTPUT LOW VOLTAGE 20 100 M AX 48 1- 07 OUTPUT LOW VOLTAGE (V) OU TP UT C UR RE NT (m A) 6 60 40 2 4 80 10 12 140 -120 0 -7 -5 -1 5 OUTPUT CURRENT vs. DRIVER OUTPUT HIGH VOLTAGE -20 -80 M AX 48 1- 08 OUTPUT HIGH VOLTAGE (V) OU TP UT C UR RE NT (m A) -3 1 -60 3-6 -4 -2 0 2 4 -100 -40 100 -40-60 -20 40 100 120 MAX1487 SUPPLY CURRENT vs. TEMPERATURE 300 M AX 48 1- 13 TEMPERATURE (°C) SU PP LY C UR RE NT (µ A) 20 60 80 500 200 600 400 0 0 140 MAX1487; DE = VCC, RE = X MAX1487; DE = 0V, RE = X 100 -50 -25 50 100 MAX481/MAX485/MAX490/MAX491 SUPPLY CURRENT vs. TEMPERATURE 300 M AX 48 1- 11 TEMPERATURE (°C) SU PP LY C UR RE NT (µ A) 25 75 500 200 600 400 0 0 125 MAX481/MAX485; DE = VCC, RE = X MAX485; DE = 0, RE = X, MAX481; DE = RE = 0 MAX490/MAX491; DE = RE = X MAX481; DE = 0, RE = VCC 100 -50 -25 50 100 MAX483/MAX487–MAX489 SUPPLY CURRENT vs. TEMPERATURE 300 M AX 48 1- 12 TEMPERATURE (°C) SU PP LY C UR RE NT (µ A) 25 75 500 200 600 400 0 0 125 MAX483; DE = VCC, RE = X MAX487; DE = VCC, RE = X MAX483/MAX487; DE = 0, RE = VCC MAX483/MAX487; DE = RE = 0, MAX488/MAX489; DE = RE = X 海纳电子资讯网： www.fpga-arm.com M A X 4 8 1 /M A X 4 8 3 /M A X 4 8 5 /M A X 4 8 7 –M A X 4 9 1 /M A X 1 4 8 7 低功耗、限摆率、 RS-485/RS-422收发器 _______________________________________________________________________________________ 7 ___________________________________________________________________ 引脚说明 MAX481 MAX483 MAX485 MAX487 MAX1487 TOP VIEW NOTE: PIN LABELS Y AND Z ON TIMING, TEST, AND WAVEFORM DIAGRAMS REFER TO PINS A AND B WHEN DE IS HIGH. TYPICAL OPERATING CIRCUIT SHOWN WITH DIP/SO PACKAGE. 1 2 3 4 8 5 VCC GND DI DE RE RO R D RtRt 7 6 D R DE RE DI ROA B 1 2 3 4 8 7 6 5 VCC B A GND DI DE RE RO DIP/SO R D 1 2 3 4 8 7 6 5 VCC A GND DERE B RO µMAX B A DI MAX481 MAX483 MAX485 MAX487 MAX1487 图1. MAX481/MAX483/MAX485/MAX487/MAX1487引脚配置与典型工作电路 µMAX — — 5 6 7 8 — 2 — 1 3 — µMAX 4 5 6 7 — — 8 — 1 — 2 — DIP/SO DIP/SO 2 3 Receiver Output Enable. RO is enabled when RE is low; RO is high impedance when RE is high. 3 4 Driver Output Enable. The driver outputs, Y and Z, are enabled by bringing DE high. They are high impedance when DE is low. If the driver outputs are enabled, the parts function as line drivers. While they are high impedance, they function as line receivers if RE is low. DIP/SO — 4 5 Driver Input. A low on DI forces output Y low and output Z high. Similarly, a high on DI forces output Y high and output Z low. 5 6, 7 Ground — 9 Noninverting Driver Output — 10 Inverting Driver Output — 3 4 6 — Noninverting Receiver Input and Noninverting Driver Output — 12 Noninverting Receiver Input 5 6 — 8 RE DE DI GND Y Z A A 7 — — B Inverting Receiver Input and Inverting Driver Output — 7 11 B Inverting Receiver Input 8 1 14 VCC Positive Supply: 4.75V ≤ VCC ≤ 5.25V — — 1, 8, 13 N.C. No Connect—not internally connected FUNCTIONNAME 431 2 Receiver Output: If A > B by 200mV, RO will be high; If A < B by 200mV, RO will be low. 2 RO PIN FUNCTIONNAME MAX481/MAX483/ MAX485/MAX487/ MAX1487 MAX488/ MAX490 MAX489/ MAX491 引脚 名称 功能 接收器输出：若A > B 200mV，则RO为高电平； 若A < B 200mV，则RO为低电平。 接收器输出使能。当RE为低电平时，RO有效； 当RE为高电平时，RO为高阻状态。 驱动器输出使能。DE变为高电平时，驱动器输出Y与Z有效； 当DE为低电平时，驱动器输出为高阻状态。 当驱动器输出有效时，器件被用作线驱动器。而高阻状态下， 若RE为低电平，则器件被用作线接收器。 驱动器输入。DI上的低电平强制输出Y为低电平，而输出Z为高电平。 同理，DI上的高电平强制输出Y为高电平，而输出Z为低电平。 地 驱动器同相输出端 驱动器反相输出端 接收器同相输入端和驱动器同相输出端 接收器同相输入端 接收器反相输入端和驱动器反相输出端 接收器反相输入端 正电源：4.75V ≤ VCC ≤ 5.25V 未连接——内部未连接 海纳电子资讯网： www.fpga-arm.com M A X 4 8 1 /M A X 4 8 3 /M A X 4 8 5 /M A X 4 8 7 –M A X 4 9 1 /M A X 1 4 8 7 ____________________________ 应用说明 MAX481/MAX483/MAX485/MAX487-MAX491以及 MAX1487是用于RS-485与RS-422通信的低功耗收发器。 MAX481、MAX485、MAX490、MAX491以及MAX1487 能够以最高 2.5Mbps的数据速率发送并接收数据；而 MAX483、MAX487、MAX488以及MAX489则用于最高 250kbps的数据速率。MAX488-MAX491是全双工收发 器，MAX481、MAX483、MAX485、MAX487以及 MAX1487是半双工收发器。另外，MAX481、MAX483、 MAX485、MAX487、MAX489、MAX491以及MAX1487 中包含驱动器使能(DE)与接收器使能(RE)控制引脚， 被禁用时，驱动器或接收器输出为高阻态。 MAX487/MAX1487: 总线上可以接128个收发器 与标准RS-485驱动器 (最多 32个收发器 )的单位负载 ( 12kΩ输入阻抗 )相比，MAX487与MAX1487具有48kΩ 输入电阻，1/4单位负载的接收器输入阻抗，在一条总线 上允许最多挂接128个收发器。MAX487/MAX1487与其他 RS-485收发器的任意组合可以允许32个收发器或更少的 收发器连接在同一条总线上。MAX481/MAX483/MAX485 与MAX488-MAX491具有标准的12 kΩ接收器输入阻抗。 低功耗、限摆率、 RS-485/RS-422收发器 8 _______________________________________________________________________________________ MAX488 MAX490 TOP VIEW 1 2 3 4 RO DI GND 8 7 6 5 A B Z Y VCC DIP/SO R D Rt Rt VCC 5 6 7 8 RO DI GND 4 GND DI RO 3 2 A B Y Z VCC D R R D 1 3VCC 4RO 2A 1 6 5 7 8 GND DI Y ZB µMAX MAX488 MAX490 NOTE: TYPICAL OPERATING CIRCUIT SHOWN WITH DIP/SO PACKAGE. MAX489 MAX491 DIP/SO TOP VIEW Rt Rt DE VCC RE GND VCC RE GND DE RO DI 9 10 12 11 B A Z Y 5 RO NC DI 2 1, 8, 13 3 6, 7 144 1 2 3 4 5 6 7 14 13 12 11 10 9 8 VCC N.C. N.C. A B Z Y N.C. RO RE DE DI GND GND R D D R D R 图2. MAX488/MAX490引脚配置与典型工作电路 图3. MAX489/MAX491引脚配置与典型工作电路 海纳电子资讯网： www.fpga-arm.com MAX483/MAX487/MAX488/MAX489: 降低EMI和反射 MAX483以及MAX487-MAX489具有摆率限制，可以减 小EMI，并降低由不恰当的终端匹配电缆引起的反射。 图 1 2给出了驱动器输出波形以及使用 M A X 4 8 1、 MAX485、MAX490、MAX491或MAX1487发送150kHz 信号时的傅立叶分析。有明显的大幅值高频谐波。 图13给出了MAX483、MAX487、MAX488或MAX489在 相同条件下发送数据时的测试结果。图13中的高频谐波 幅值要低得多，因此，从根本上抑制了EMI。 M A X 4 8 1 /M A X 4 8 3 /M A X 4 8 5 /M A X 4 8 7 –M A X 4 9 1 /M A X 1 4 8 7 低功耗、限摆率、 RS-485/RS-422收发器 _______________________________________________________________________________________ 9 R R Y Z VOD VOC RECEIVER OUTPUT TEST POINT 1kΩ 1kΩ S1 S2 VCC CRL 15pF DI DE 3V Y Z CL1 CL2 A B RO RE RDIFF VID OUTPUT UNDER TES