ＳＴＣ Ｉｎｔｅｒｎａｔｉｏｎａｌ Ｌｉｍｉｔｅｄ ｈｔｔｐ：／／ｗｗｗ．ｍｃｕ－ｍｅｍｏｒｙ．ｃｏｍ STC485E ±15kV ESD-Protected,Slew-Rate-Limited, Fail-Safe,True RS-485 Transceivers General Description The STC485E is ±15kV electrostatic discharge (ESD)-protected, high-speed transceivers for RS-485 communication that contains one driver and one receiver. These devices feature fail-safe circuitry, which guarantees a logic-high receiver output when the receiver inputs are open, shorted or idle. This means that the receiver output will be a logic high if all transmitters on a terminated bus are disabled (high impedance). The STC485E features reduced slew-rate driver that minimizes EMI and reduces reflections caused by improperly terminated cables, allowing error-free data transmission up to 500kbps. All devices feature enhanced ESD protection. All transmitter outputs and receiver inputs are protected to ±15kV using the Human Body Model. These transceivers typically draw 400µA of supply current when unloaded, or when fully loaded with the drivers disabled. All devices have a 1/8-unit-load receiver input impedance that allows up to 256 transceivers on the bus. The STC485E is intended for half -duplex communications. Applications RS-485 Transceivers Level Translators Transceivers for EMI-Sensitive Applications Industrial-Control Local Area Networks Features ESD Protection for RS-485 I/O Pins ±15kV— Human Body Model ±15kV— IEC 1000-4-2, Air-Gap Discharge True Fail-Safe Receiver While Maintaining EIA/TIA-485 Compatibility Enhanced Slew-Rate Limiting Facilitates Error-Free Data Transmission 2nA Low-Current Shutdown Mode –7V to +12V Common-Mode Input Voltage Range Allows up to 256 Transceivers on the Bus Thermal Shutdown Current-Limiting for Driver Overload Protection Ordering Information PART TEMP. RANGE PIN-PACKAGE STC485EESA -40°C to +85°C 8 SO STC485EEPA -40°C to +85°C 8 Plastic DIP Selector Guide PART NUMBER STC485E GUARANTEED DATA RATE (Mbps) 0.5 Low- Power SLEW-RATE Shutdown LIMITED Yes Yes ＳＴＣ４８５Ｅ Ｄａｔａｓｈｅｅｔ Ｒｅｖ．０．１， Ｄｅｃ．２００５ DRIVER/ SHUTDOWN Transceivers ±15kV RECEIVER CURRENT On ESD ENABLE (nA) Bus PROTECTION Yes 2 256 Yes PIN COUNT Ｐａｇｅ ｏｆ １１ １ 8 ＳＴＣ Ｉｎｔｅｒｎａｔｉｏｎａｌ Ｌｉｍｉｔｅｄ ｈｔｔｐ：／／ｗｗｗ．ｍｃｕ－ｍｅｍｏｒｙ．ｃｏｍ Absolute Maximum Ratings Supply Voltage (VCC) … … … … … … … … … … … … … … … … … … 7V Control Input Voltage (/RE, DE) … … … … … … -0.3V to (VCC + 0.3V) Driver Input Voltage (DI) … … … … … … … … … -0.3V to (VCC + 0.3V) Driver Output Voltage (A, B) … … … … … … … … … … … -7.5V to 12.5V Receiver Input Voltage (A, B) … … … … … … … … … … … -7.5V to 12.5V Receiver Output Voltage (RO) … … … … … … … -0.3V to (VCC + 0.3V) Continuous Power Dissipation (TA = +70°C) 8-Pin Plastic DIP (derate 9.09mW/°C above +70°C… … … … 727mW 8-Pin SO (derate 5.88mW/°C above +70°… … … … … … … … 471mW Operating Temperature Ranges STC485EE_ _ … … … … … … … … … … … … … … … … -40°C to +85°C Storage Temperature Range… … … … … … … … … … -65°C to +160°C Lead Temperature (soldering, 10sec) … … … … … … … … … … +300°C 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. DC Electrical Characteristics (VCC = +5V ±5%, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = +5V and TA = +25°C.) (Note 1) PARAMETER DRIVER Differential Driver Output (No Load) Differential Driver Output Change in Magnitude of Driver Differential Output Voltage (Note 2) Driver Common-Mode Output Voltage SYMBOL CONDITIONS MIN VOD1 VOD2 Figure 2 R= 50O, Figure 2 ? VOD TYP MAX UNITS 5 V V R= 50O?, Figure 2 0.2 V VOC R= 50O, Figure 2 3 V ? VOC R= 50O, Figure 2 0.2 V Input High Voltage Input Low Voltage VIH VIL DE, DI, /RE DE, DI, /RE 0.8 V V DI Input Hysteresis VHYS Change in Magnitude of Common -Mode Output Voltage (Note 2) Input Current (A, B) Driver Short-Circuit Output Current (Note 3) RECEIVER Receiver Differential Threshold Voltage Receiver Input Hysteresis Receiver Output High Voltage Receiver Output Low Voltage Three-State (High Impedance) Output Current at Receiver Receiver Input Resistance Receiver Short-Circuit Output Current SUPPLY CURRENT Supply Current Supply Current in Shutdown Mode IIN2 1.5 2.0 100 UM3085E DE = 0V, VCC = 0V or 5V 1.0 VIN = -7V -0.8 IOSD VOUT = -7V VOUT = 12V VTH ? VTH VOH VOL -7V=VCM=12V VCM = 0V IOUT = -1.5mA, VID = 200mV IOUT = 2.5mA, VID = 200mV IOZR VCC = 5V, 0V=VOUT\=VCC RIN IOSR -7V=VCM=12V 0V=VRO=VCC ICC ISHDN ESD Protection for A, B mV VIN = 12V -250 250 -0.2 mA -0.05 0.4 V mV V V ±1 µA ±60 kO？ mA 25 VCC –1.5 96 ±8 DE = VCC, /RE = 0V 0.3 or VCC DE = 0V, /RE = 0V 0.25 DE = 0V, /RE = VCC, DI = VCC or 0V 0.002 No load, DI = 0V or VCC Human Body Model IEC 1000-4-2 Air Discharge mA mA 10 ±15 ±15 µA kV Note 1: All currents into the device are positive; all currents out of the device are negative. All voltages are referred to device ground unless otherwise noted. Note 2: VOD and VOC are the changes in VOD and VOC, respectively, when the DI input changes state. Note 3: Maximum current level applies to peak current just prior to foldback-current limiting; minimum current level applies during current limiting. ＳＴＣ４８５Ｅ Ｄａｔａｓｈｅｅｔ Ｒｅｖ．０．１， Ｄｅｃ．２００５ Ｐａｇｅ ｏｆ １１ ２ ＳＴＣ Ｉｎｔｅｒｎａｔｉｏｎａｌ Ｌｉｍｉｔｅｄ ｈｔｔｐ：／／ｗｗｗ．ｍｃｕ－ｍｅｍｏｒｙ．ｃｏｍ Switching Characteristics (VCC = +5V ±5%, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = +5V and TA = +25°C.) (Note 1) PARAMETER Driver Input-to-Output SYMBOL CONDITIONS tDPLH Figures 4 and 6, RDIFF = 54? , CL1 = CL2 = 100pF tDPHL Driver Output Skew | tDPLH - tDPHL | tDSKEW Driver Rise or Fall Time tDR, tDF Figures 4 and 6, RDIFF = 54? , CL1 = CL2 = 100pF Figures 4 and 6, RDIFF = 54? , CL1 = CL2 = 100pF Maximum Data Rate fMAX Driver Enable to Output High Driver Enable to Output Low Driver Disable Time from Low Driver Disable Time from High tDZH tDZL tDLZ tDHZ Figures 5 and 7, CL = 100pF, S2 closed Figures 5 and 7, CL = 100pF, S1 closed Figures 5 and 7, CL = 15pF, S1 closed Figures 5 and 7, CL = 15pF, S2 closed tRPLH, tRPHL tRZL tRZH Figures 11 and 13; | VID | =?2.0V; rise and fall time of VID =?15ns Figures 8 and 10; | VID | =?2.0V; rise and fall time of VID =?15ns Figures 3 and 9, CL = 100pF, S1 closed Figures 3 and 9, CL = 100pF, S2 closed tRLZ Receiver Input to Output | tRPLH - tRPHL | Differential Receiver Skew Receiver Enable to Output Low Receiver Enable to Output High MIN TYP MAX UNITS 250 720 1000 250 720 1000 -3 ±100 ns 530 750 ns 200 ns 500 kbps 2500 2500 100 100 ns ns ns ns 127 200 ns 3 ±30 ns 20 20 50 50 ns ns Figures 3 and 9, CL = 100pF, S1 closed 20 50 ns tRHZ Figures 3 and 9, CL = 100pF, S2 closed 20 50 ns 600 ns tRSKD 3 Receiver Disable Time from Low Receiver Disable Time from High Time to Shutdown Driver Enable from Shutdown-to-Output High Driver Enable from Shutdown-to-Output Low Receiver Enable from Shutdown-to-Output High tSHDN (Note 4) tDZH(SHDN) Figures 5 and 7, CL = 15pF, S2 closed 4500 ns tDZL(SHDN) Figures 5 and 7, CL = 15pF, S1 closed 4500 ns tRZH(SHDN) Figures 3 and 9, CL = 100pF, S2 closed 3500 ns Receiver Enable from Shutdown-to-Output Low tRZL(SHDN) Figures 3 and 9, CL = 100pF, S1 closed 3500 ns ＳＴＣ４８５Ｅ Ｄａｔａｓｈｅｅｔ Ｒｅｖ．０．１， Ｄｅｃ．２００５ 50 200 Ｐａｇｅ ｏｆ １１ ３ ＳＴＣ Ｉｎｔｅｒｎａｔｉｏｎａｌ Ｌｉｍｉｔｅｄ ｈｔｔｐ：／／ｗｗｗ．ｍｃｕ－ｍｅｍｏｒｙ．ｃｏｍ Typical Operating Characteristics (VCC = +5V, TA = +25°C, unless otherwise noted.) ＯＵＴＰＵＴ ＣＵＲＲＥＮＴ ｖｓ．ＲＥＣＥＩＶＥＲ ＯＵＴＰＵＴ ＬＯＷ ＶＯＬＴＡＧＥ ＮＯ－ＬＯＡＤ ＳＵＰＰＬＹ ＣＵＲＲＥＮＴ ｖｓ．ＴＥＭＰＥＲＡＴＵＲＥ ５２５ ６０ ３０ ５０ ２５ ４５０ ４２５ ４００ ３７５ ＯＵＴＰＵＴ ＣＵＲＲＥＮＴ（ｍＡ） ４７５ ＯＵＴＰＵＴ ＣＵＲＲＥＮＴ（ｍＡ） ＮＯ－ＬＯＡＤ ＳＵＰＰＬＹＣＵＲＲＥＮＴ（ｕＡ） ５００ ＯＵＴＰＵＴ ＣＵＲＲＥＮＴ ｖｓ．ＲＥＣＥＩＶＥＲ ＯＵＴＰＵＴ ＨＩＧＨ ＶＯＬＴＡＧＥ ４０ ３０ ２０ ２０ １５ １０ ３５０ ５ １０ ３２５ －６０ －４０ －２０ ０ ２０ ４０ ６０ ８０ ０ １００ １ ２ ３ ４ ０ ５ ＳＨＵＴＤＯＷＮ ＣＵＲＲＥＮＴ ｖｓ．ＴＥＭＰＥＲＡＴＵＲＥ ＲＥＣＥＩＶＥＲ ＯＵＴＰＵＴ ＬＯＷ ＶＯＬＴＡＧＥ ｖｓ．ＴＥＭＰＥＲＡＴＵＲＥ ２０ １８ １ ２ ３ ４ ５ ＯＵＴＰＵＴ ＨＩＧＨ ＶＯＬＴＡＧＥ （Ｖ） ＯＵＴＰＵＴ ＬＯＷ ＶＯＬＴＡＧＥ （Ｖ） Ｔ Ｅ Ｍ Ｐ Ｅ Ｒ Ａ Ｔ Ｕ Ｒ Ｅ （℃） ＲＥＣＥＩＶＥＲ ＯＵＴＰＵＴ ＨＩＧＨ ＶＯＬＴＡＧＥ ｖｓ．ＴＥＭＰＥＲＡＴＵＲＥ ０．５０ ４．５ ０．４５ ４．４ １６ １４ １２ １０ ８ ６ ４ ０．４０ ＯＵＴＰＵＴ ＶＯＬＴＡＧＥ（Ｖ） ＯＵＴＰＵＴ ＬＯＷ ＶＯＬＴＡＧＥ（Ｖ） ＳＨＵＴＤＯＷＮ ＣＵＲＲＥＮＴ（ｎＡ） ０ ０ ３００ ０．３５ ０．３０ ０．２５ ０．２０ ０ ０．１０ －６０ －４０ －２０ ０ ２０ ４０ ６０ ８０ １００ ４．１ ４．０ ３．８ －６０ －４０ －２０ Ｔ Ｅ Ｍ Ｐ Ｅ Ｒ Ａ Ｔ Ｕ Ｒ Ｅ （℃） ４．２ ３．９ ０．１５ ２ ４．３ ０ ２０ ４０ ６０ ８０ －６０ －４０ －２０ １００ ＲＥＣＥＩＶＥＲ ＰＲＯＰＡＧＡＴＩＯＮ ＤＥＬＡＹ （５００ｋｂｐｓ ＭＯＤＥ）ｖｓ．ＴＥＭＰＥＲＡＴＵＲＥ ２０ ４０ ６０ ８０ １００ ＤＲＩＶＥＲ ＰＲＯＰＡＧＡＴＩＯＮ ＤＥＬＡＹ （１ １ ５ ｋｂｐｓ ＭＯＤＥ）ｖｓ．ＴＥＭＰＥＲＡＴＵＲＥ ＲＥＣＥＩＶＥＲ ＰＲＯＰＡＧＡＴＩＯＮ ＤＥＬＡＹ （１ ０ Ｍｂｐｓ ＭＯＤＥ）ｖｓ．ＴＥＭＰＥＲＡＴＵＲＥ １４０ ０ Ｔ Ｅ Ｍ Ｐ Ｅ Ｒ Ａ Ｔ Ｕ Ｒ Ｅ （℃） Ｔ Ｅ Ｍ Ｐ Ｅ Ｒ Ａ Ｔ Ｕ Ｒ Ｅ （℃） １１２ ２．２０ １３５ １３０ １２５ １２０ ＰＲＯＰＡＧＡＴＩＯＮ ＤＥＬＡＹ（ｕｓ） ＰＲＯＰＡＧＡＴＩＯＮ ＤＥＬＡＹ（ｎｓ） ＰＲＯＰＡＧＡＴＩＯＮ ＤＥＬＡＹ（ｎｓ） １１０ １０８ １０６ １０４ １０２ １００ ９８ ２．１５ ２．１０ ２．０５ ２．００ １．９５ ９６ ９４ １１５ －６０ －４０ －２０ ０ ２０ ４０ ６０ ８０ １００ Ｔ Ｅ Ｍ Ｐ Ｅ Ｒ Ａ Ｔ Ｕ Ｒ Ｅ （℃） ＳＴＣ４８５Ｅ Ｄａｔａｓｈｅｅｔ Ｒｅｖ．０．１， Ｄｅｃ．２００５ －６０ －４０ －２０ ０ ２０ ４０ ６０ ８０ Ｔ Ｅ Ｍ Ｐ Ｅ Ｒ Ａ Ｔ Ｕ Ｒ Ｅ （℃） １００ １．９０ －６０ －４０ －２０ ０ ２０ ４０ ６０ ８０ Ｔ Ｅ Ｍ Ｐ Ｅ Ｒ Ａ Ｔ Ｕ Ｒ Ｅ （℃） Ｐａｇｅ ｏｆ １１ ４ １００ ＳＴＣ Ｉｎｔｅｒｎａｔｉｏｎａｌ Ｌｉｍｉｔｅｄ ｈｔｔｐ：／／ｗｗｗ．ｍｃｕ－ｍｅｍｏｒｙ．ｃｏｍ Typical Operating Characteristics(continued) (VCC = +5V, TA = +25°C, unless otherwise noted.) ＤＲＩＶＥＲ ＰＲＯＰＡＧＡＴＩＯＮ ＤＥＬＡＹ （１ ０ Ｍ ｂ ｐ ｓ Ｍ Ｏ Ｄ Ｅ）ｖ ｓ ． Ｔ Ｅ Ｍ Ｐ Ｅ Ｒ Ａ Ｔ Ｕ Ｒ Ｅ ＤＲＩＶＥＲ ＤＩＦＦＥＲＥＮＴＩＡＬ ＯＵＴＰＵＴ ＶＯＬＴＡＧＥ ｖｓ．ＴＥＭＰＥＲＡＴＵＲＥ ９２０ ６０ １．９０ ８８０ ５５ １．８９ ８００ ７６０ ７２０ ６８０ ６４０ ６００ ５０ ＯＵＴＰＵＴ ＶＯＬＴＡＧＥ（Ｖ） ８４０ ＰＲＯＰＡＧＡＴＩＯＮ ＤＥＬＡＹ（ｎｓ） ＰＲＯＰＡＧＡＴＩＯＮ ＤＥＬＡＹ（ｎｓ） ＤＲＩＶＥＲ ＰＲＯＰＡＧＡＴＩＯＮ ＤＥＬＡＹ （５００ｋｂｐｓ ＭＯＤＥ）ｖｓ． ＴＥＭＰＥＲＡＴＵＲＥ ４５ ４０ ３５ ３０ ２０ ５２０ －６０ －４０ －２０ ０ ２０ ４０ ６０ ８０ １００ １．８６ １．８５ １．８３ －６０ －４０ －２０ Ｔ Ｅ Ｍ Ｐ Ｅ Ｒ Ａ Ｔ Ｕ Ｒ Ｅ （℃） ０ ２０ ４０ ６０ ８０ １００ －６０ －４０ －２０ ＯＵＴＰＵＴ ＣＵＲＲＥＮＴ ｖｓ． ＤＲＩＶＥＲ ＯＵＴＰＵＴ ＬＯＷ ＶＯＬＴＡＧＥ １００ ６０ ８０ １００ －９０ ＯＵＴＰＵＴ ＣＵＲＲＥＮＴ（ｍＡ） ＯＵＴＰＵＴ ＣＵＲＲＥＮＴ（ｍＡ） ０．１ ４０ －１００ １２０ １ ２０ ＯＵＴＰＵＴ ＣＵＲＲＥＮＴ ｖｓ． ＤＲＩＶＥＲ ＯＵＴＰＵＴ ＨＩＧＨ ＶＯＬＴＡＧＥ １４０ １０ ０ Ｔ Ｅ Ｍ Ｐ Ｅ Ｒ Ａ Ｔ Ｕ Ｒ Ｅ （℃） Ｔ Ｅ Ｍ Ｐ Ｅ Ｒ Ａ Ｔ Ｕ Ｒ Ｅ （℃） ＤＲＩＶＥＲ ＯＵＴＰＵＴ ＣＵＲＲＥＮＴ ｖｓ．ＤＩＦＦＥＲＥＮＴＩＡＬ ＯＵＴＰＵＴ ＶＯＬＴＡＧＥ ＯＵＴＰＵＴ ＣＵＲＲＥＮＴ（ｍＡ） １．８７ １．８４ ２５ ５６０ １．８８ １００ ８０ ６０ ４０ －８０ －７０ －６０ －５０ －４０ －３０ －２０ ２０ ０．０１ －１０ ０ ０ ０ １ ２ ３ ４ ５ ＤＩＦＦＥＲＥＮＴＩＡＬ ＯＵＴＰＵＴ ＶＯＬＴＡＧＥ（Ｖ） ０ ２ ４ ６ ８ １０ ＯＵＴＰＵＴ ＬＯＷ ＶＯＬＴＡＧＥ（Ｖ） １２ －８ －６ －４ －２ ０ ２ ４ ６ ＯＵＴＰＵＴ ＨＩＧＨ ＶＯＬＴＡＧＥ （Ｖ） Typical Operating Characteristics(continued) (VCC = +5V, TA = +25°C, unless otherwise noted.) ＲＥＣＥＩＶＥＲ ＰＲＯＰＡＧＡＴＩＯＮ ＤＥＬＡＹ ＤＲＩＶＥＲ ＰＲＯＰＡＧＡＴＩＯＮ ＤＥＬＡＹ ５Ｖ／ｄｉｖ ＤＩ Ｖ Ａ－ Ｖ Ｂ ２Ｖ／ｄｉｖ ＲＯ ５Ｖ／ｄｉｖ ２．５Ｖ／ｄｉｖ Ｖ Ｙ－ Ｖ Ｚ ５０ｎｓ／ｄｉｖ ＳＴＣ４８５Ｅ Ｄａｔａｓｈｅｅｔ Ｒｅｖ．０．１， Ｄｅｃ．２００５ ５０ｎｓ／ｄｉｖ Ｐａｇｅ ｏｆ １１ ５ ＳＴＣ Ｉｎｔｅｒｎａｔｉｏｎａｌ Ｌｉｍｉｔｅｄ ｈｔｔｐ：／／ｗｗｗ．ｍｃｕ－ｍｅｍｏｒｙ．ｃｏｍ Pin Description PIN NAME 1 RO 2 /RE FUNCTION Receiver Output. If A > B by -50mV, RO will be high; if A < B by 200mV, RO will be low. Receiver Output Enable. RO is enabled when /RE is low; RO is high impedance when /RE is high. If /RE is high and DE is low, the device will enter a low-power shutdown mode. Driver Output Enable. The driver outputs are enabled by bringing DE high. They are high impedance 3 DE when DE is low. If /RE is high and DE is low, the device will enter a low-power shutdown mode. 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. 4 DI 5 6 7 8 GND Driver Input. A low on DI forces output A low and output B high. Similarly, a high on DI forces output A high and output B low. Ground A Noninverting Receiver Input and Noninverting Driver Output B Inverting Receiver Input and Inverting Driver Output VCC Positive Supply: VCC=5V±5% Function Tables Table 1. Transmitting INPUTS Table 2. Receiving OUTPUTS /RE DE DI B A X 1 1 0 0 1 0 0 1 1 0 X High-Z X High-Z X 0 1 INPUTS MODE OUTPUTS MODE /RE DE A, B RO Normal 0 X =?-0.05V Normal 0 X =?-0.2V High-Z Normal X Inputs Open Normal High-Z Shutdown 0 1 1 0 1 0 X High-Z Shutdown X = Don’t care; High-Z = High impedance Normal Normal X = Don’t care; High-Z = High impedance ＴＯＰ ＶＩＥＷ ＳＴＣ４８５Ｅ ＲＯ １ Ｒ ８ Ｖｃｃ ＲＯ ＲＥ ２ ７ Ｂ ＲＥ ＤＥ ３ ６ Ａ ＤＥ ５ ＧＮＤ ＤＩ ＤＩ ４ Ｄ １ Ｒ ２ Ｖｃｃ ７ Ｂ ３ ６ Ａ ４ Ｄ ＤＩＰ／ＳＯ ＤＥ ０．１ｕＦ ８ Ｄ Ｂ Ｒｔ Ｒｔ Ａ ５ ＧＮＤ ＤＩ ＲＯ Ｒ ＲＥ Figure 1. STC485E / Pin Configuration and Typical Operating Circuit ＳＴＣ４８５Ｅ Ｄａｔａｓｈｅｅｔ Ｒｅｖ．０．１， Ｄｅｃ．２００５ Ｐａｇｅ ｏｆ １１ ６ ＳＴＣ Ｉｎｔｅｒｎａｔｉｏｎａｌ Ｌｉｍｉｔｅｄ ｈｔｔｐ：／／ｗｗｗ．ｍｃｕ－ｍｅｍｏｒｙ．ｃｏｍ Detailed Description The STC485E high-speed transceivers for RS-485 communication contain one driver and one receiver. These devices feature fail-safe circuitry, which guarantees a logic-high receiver output when the receiver inputs are open or shorted, or when they are connected to a terminated transmission line with all drivers disabled (see the Fail-Safe section). The STC485E feature reduced slew-rate drivers that minimize EMI and reduce reflections caused by improperly terminated cables, allowing error-free data transmission up to 500kbps (see the Reduced EMI and Reflections section). All of these parts operate from a single +5V supply. Drivers are output short-circuit current limited. Thermal shutdown circuitry protects drivers against excessive power dissipation. When activated, the thermal shutdown circuitry places the driver outputs into a high impedance state. Fail-Safe The STC485E guarantees a logic-high receiver output when the receiver inputs are shorted or open, or when they are connected to a terminated transmission line with all drivers disabled. This is done by setting the receiver threshold between –50 mV and -200mV. If the differential receiver input voltage (A-B) is greater than or equal to -50mV, RO is logic high. If A-B is less than or equal to -200mV, RO is logic low. In the case of a terminated bus with all transmitters disabled, the receiver’s differential input voltage is pulled to 0V by the termination. With the receiver thresholds of the STC485E, , this results in a logic high with a 50mV minimum noise margin. Unlike previous fail-safe devices, the -50mV to -200mV threshold complies with the ±200 mV EIA/TIA-485 standard. ±15kV ESD Protection As with all STC devices, ESD-protection structures are incorporated on all pins to protect against electrostatic discharges encountered during handling and assembly. The driver outputs and receiver inputs of the STC485E have extra protection against static electricity. Union’s engineers have developed state-of-the-art structures to protect these pins against ESD of ±15kV without damage. The ESD-protected pins are tested with reference to the ground pin in a powered-down condition. They are tested to ±15kV using the Human Body Model. ESD Test Conditions ESD performance depends on a variety of conditions. Contact Union for a reliability report that documents test setup, test methodology, and test results. Human Body Model Figure 11a shows the Human Body Model and Figure 11b shows the current waveform it generates when discharged into a low impedance. 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? r?esistor. 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. All pins require this protecduring test and assembly. All pins require this protection, not just RS-485 inputs and outputs. ＳＴＣ４８５Ｅ Ｄａｔａｓｈｅｅｔ Ｒｅｖ．０．１， Ｄｅｃ．２００５ Ｐａｇｅ ｏｆ １１ ７ ＳＴＣ Ｉｎｔｅｒｎａｔｉｏｎａｌ Ｌｉｍｉｔｅｄ ｈｔｔｐ：／／ｗｗｗ．ｍｃｕ－ｍｅｍｏｒｙ．ｃｏｍ Applications Information 256 Transceivers on the Bus The standard RS-485 receiver input impedance is 12kO?(one-unit load), and the standard driver can drive up to 32 unit loads. The STC family of trans -ceivers have a 1/8-unit-load receiver input impe -dance (96kO), allowing up to 256 transceivers to be connected in parallel on one communication line. Any combination of these devices and/or other RS-485 transceivers with a total of 32 unit loads or less can be connected to the line. Reduced EMI and Reflections The STC485E is slew-rate limited, minimizing EMI and reducing reflections caused by improperly terminated cables. Figure 12 shows the same signal displayed for a STC485E, transmitting under the same conditions. In general, a transmitter’s rise time relates directly to the length of an unterminated stub, which can be driven with only minor waveform reflections. The following equation expresses this relationship conservatively: Length = tRISE / (10 x 1.5ns/ft) where tRISE is the transmitter’s rise time. A system can work well with longer unterminated stubs, even with severe reflections, if the waveform settles out before the UART samples them. Low-Power Shutdown Mode Low-power shutdown mode is initiated by bringing both /RE high and DE low. In shutdown, the devices typically draw only 2 nA of supply current. /RE and DE may be driven simultaneously; the parts are guaranteed not to enter shutdown if /RE is high and DE is low for less than 50ns. If the inputs are in this state for at least 600ns, the parts are guaran -teed to enter shutdown. Enable times tZH and tZL in the Switching Characteristics tables assume the part was not in a low-power shutdown state. Enable times tZH(SHDN) and tZL(SHDN) assume the parts were shut down. It takes drivers and receivers longer to become enabled from low-power shutdown mode (tZH(SHDN), tZH(SHDN)) than from driver/receiver -disable mode (tZH, tZL). Driver Output Protection Two mechanisms prevent excessive output current and power dissipation caused by faults or by bus contention. The first, 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). The second, a thermal shutdown circuit, forces the driver outputs into a high-impedance state if the die temperature becomes excessive. Line Length vs. Data Rate The RS-485/RS-422 standard covers line lengths up to 4000 feet. For line lengths greater than 4000 feet, repeater is required. Typical Applications The STC485E transceivers are designed for bidirectional data communications on multipoint bus transmission lines. Figures 14 show typical network applications circuits. To minimize reflections, the line should be terminated at both ends in its characteristic impedance, and stub lengths off the main line should be kept as short as possible. ＳＴＣ４８５Ｅ Ｄａｔａｓｈｅｅｔ Ｒｅｖ．０．１， Ｄｅｃ．２００５ Ｐａｇｅ ｏｆ １１ ８ ＳＴＣ Ｉｎｔｅｒｎａｔｉｏｎａｌ Ｌｉｍｉｔｅｄ ｈｔｔｐ：／／ｗｗｗ．ｍｃｕ－ｍｅｍｏｒｙ．ｃｏｍ Ｙ １Ｋ ＴＥＳＴ ＰＯＩＮＴ ＲＥＣＥＩＶＥＲ ＯＵＴＰＵＴ ＋ ＣＲＬ １５ｐＦ Ｒ ＶＤＤ Ｒ ＶＣＣ Ｓ１ １Ｋ ＶＣＣ Ｓ２ Ｚ Figure 2. Driver DC Test Load Figure 3. Receiver Enable/Disable Timing Test Load ３Ｖ ＤＥ ＣＬ１ Ｙ ＤＩ ＲＤＩＦＦ ＶＤＤ２ ＯＵＴＰＵＴ ＵＮＤＥＲ ＴＥＳＴ Ｚ ＣＬ２ Ｓ１ ５００ Ω ＶＣＣ ＋ ＣＬ Ｓ２ Figure 4. Driver Timing Test Circuit ＤＩ ５Ｖ Ｏ Figure 5. Driver Enable and Disable Timing Test Load １．５Ｖ １．５Ｖ ｔ ＤＰＬＨ ＤＥ ｔ ＤＰＨＬ １／２ＶＯ Ｚ Ｙ ＶＯ ０ －ＶＯ Ｏ ｔＤＺＬ（ＳＨＤＮ）． ｔ Ｄ Ｚ Ｌ Ｖ ＤＩＦＦ ＝Ｖ（Ｙ）－Ｖ（Ｚ） ９０％ ９０％ ｔＤＲ ＶＯＬ＋０．５Ｖ ＯＵＴＰＵＴ ＮＯＲＭＡＬＬＹ ＨＩＧＨ Ｙ．Ｚ Ｏ １０％ ｔＤＬ Ｚ ２．３Ｖ ＯＵＴＰＵＴ ＮＯＲＭＡＬＬＹ ＬＯＷ ＶＯＬ １０％ １．５Ｖ １．５Ｖ Ｙ．Ｚ ＶＯ １／２ＶＯ ＶＤＩＦＦ ５Ｖ ＶＯＨ＋０．５Ｖ ２．３Ｖ ｔＤＺＨ （ＳＨＤＮ）． ｔ Ｄ Ｚ Ｈ ｔＤＦ ｔＤＨ Ｚ ｔ ＳＫＥＷ＝｜ ｔ ＤＰＬＨ － ｔ ＤＰＨＬ｜ Figure 6. Driver Propagation Delays Figure 7. Driver Enable and Disable Times ＲＥ ＲＯ １Ｖ －１Ｖ ＶＯＨ ＶＯＬ １．５Ｖ ｔＲＰＨＬ Ａ Ｂ １．５Ｖ ＯＵＴＰＵＴ ５Ｖ Ｏ ＶＣＣ ｔＲＰＬＨ １．５Ｖ １．５Ｖ ｔＲ ＺＬ（ＳＨＤＮ）． ｔ Ｒ Ｚ Ｌ １．５Ｖ ＯＵＴＰＵＴ ＮＯＲＭＡＬＬＹ ＬＯＷ ＲＯ １．５Ｖ ＩＮＰＵＴ ＶＯＬ＋０．５Ｖ ＯＵＴＰＵＴ ＮＯＲＭＡＬＬＹ ＨＩＧＨ Ｏ ｔＲ ＺＨ （ＳＨＤＮ）． ｔ Ｒ Ｚ Ｈ Figure 8. Receiver Propagation Delays Ｒ ＶＤ ＶＯＨ＋０．５Ｖ ｔＲ Ｈ Ｚ Figure 9. Receiver Enable and Disable Times Ｂ ＡＴＥ ｔＲ Ｌ Ｚ ＲＯ Ａ ＲＥＣＥＩＶＥＲ ＯＵＴＰＵＴ Figure 10. Receiver Propagation Delay Test Circuit ＳＴＣ４８５Ｅ Ｄａｔａｓｈｅｅｔ Ｒｅｖ．０．１， Ｄｅｃ．２００５ Ｐａｇｅ ｏｆ １１ ９ ＳＴＣ Ｉｎｔｅｒｎａｔｉｏｎａｌ Ｌｉｍｉｔｅｄ ｈｔｔｐ：／／ｗｗｗ．ｍｃｕ－ｍｅｍｏｒｙ．ｃｏｍ ＲＣ １ＭΩ ＣＨＡＲＧＥ－ＣＵＲＲＥＮＴ ＬＩＭＩＴ ＲＥＳＩＳＴＯＲ ＨＩＧＨ－ ＶＯＬＴＡＧＥ ＤＣ ＳＯＵＲＣＥ ＣＳ １００ｐＦ ＲＤ １５００ Ω ＤＩＳＣＨＡＲＧＥ ＲＥＳＩＳＴＡＮＣＥ ＤＥＶＩＣＥ ＵＮＤＥＲ ＴＥＳＴ ＳＴＯＲＡＧＥ ＣＡＰＡＣＩＴＯＲ Figure 11a. Human Body ESD Test Model Figure 11b. Human Body Current Waveform Figure 12. Driver Output Waveform and FFT Plot Figure 13. STC485E System Differential Voltage at 50kHz of STC485E, Transmitting a 20kHz Signal Driving 4000ft of Cable １２０ Ω １２０ Ω Ｂ ＤＩ ＤＥ Ｂ Ｄ Ｄ ＤＩ ＤＥ ＲＯ Ａ Ｂ Ｂ Ａ Ａ Ａ Ｒ Ｒ ＲＥ Ｒ ＳＴＣ４８５Ｅ Ｒ Ｄ Ｄ ＤＩ ＲＯ ＲＥ ＤＥ ＲＯ ＲＥ ＤＩ ＤＥ ＲＯ ＲＥ Figure 16. Typical Half-Duplex RS-485 Network ＳＴＣ４８５Ｅ Ｄａｔａｓｈｅｅｔ Ｒｅｖ．０．１， Ｄｅｃ．２００５ Ｐａｇｅ ｏｆ １１ １０ ＳＴＣ Ｉｎｔｅｒｎａｔｉｏｎａｌ Ｌｉｍｉｔｅｄ ｈｔｔｐ：／／ｗｗｗ．ｍｃｕ－ｍｅｍｏｒｙ．ｃｏｍ Package Information ＩＮＣＨＥＳ ＤＩＭ Ｄ Ａ１ Ａ ０°－ ８° ０．１０１ｍｍ ０．００４ｉｎ． Ｅ ＭＡＸ ＭＩＮ ＭＡＸ Ａ ０．０５３ ０．０６９ １．３５ １．７５ Ａ１ ０．００４ ０．０１０ ０．１０ ０．２５ Ｂ ０．０１４ ０．０１９ ０．３５ ０．４９ Ｃ ０．００７ ０．０１０ ０．１９ ０．２５ Ｅ ０．１５０ ０．１５７ ３．８０ ４．００ ｅ Ｃ Ｌ ＳＯ ＳＭＡＬＬ ＯＵＴＬＩＮＥ ＰＡＣＫＡＧＥ （０ ． １ ５ ０ ｉ ｎ ． ） Ｈ Ｂ ｅ ＭＩＬＬＩＭＥＴＥＲＳ ＭＩＮ ０．０５０ １．２７ Ｈ ０．２２８ ０．２４４ ５．８０ ６．２０ Ｌ ０．０１６ ０．０５０ ０．４０ １．２７ ＤＩＭ ＰＩＮＳ Ｄ ＩＮＣＨＥＳ ＭＩＬＬＩＭＥＴＥＲＳ ＭＩＮ ＭＡＸ ＭＩＮ ＭＡＸ ８ ０．１８９ ０．１９７ ４．８０ ５．００ Ｄ １４ ０．３３７ ０．３４４ ８．５５ ８．７５ Ｄ １６ ０．３８６ ０．３９４ ９．８０ １０．００ ２１－００４１Ａ Ｅ Ｅ１ Ｄ Ａ３ Ａ Ｌ Ａ２ ｅ Ｂ ＳＴＣ４８５Ｅ Ｄａｔａｓｈｅｅｔ Ｒｅｖ．０．１， Ｄｅｃ．２００５ ＭＡＸ － ０．２００ － ５．０８ － ０．３８ － ０．１２５ ０．１７５ ３．１８ ４．４５ Ａ３ ０．０５５ ０．０８０ １．４０ ２．０３ Ｂ ０．０１６ ０．０２２ ０．４１ ０．５６ Ｂ１ ０．０４５ ０．０６５ １．１４ １．６５ Ｃ ０．００８ ０．０１２ ０．２０ ０．３０ Ｄ１ ０．００５ ０．０８０ ０．１３ ２．０３ Ｅ ０．３００ ０．３２５ ７．６２ ８．２６ Ｅ１ ０．２４０ ０．３１０ ６．１０ ７．８７ ｅ ０．１００ － ２．５４ － ｅＡ ０．３００ － ７．６２ － ｅＢ － ０．４００ － １０．１６ Ｌ ０．１１５ ０．１５０ ２．９２ ３．８１ Ｄ１ Ｐｌａｓｔｉｃ ＤＩＰ ＰＬＡＳＴＩＣ ＤＵＡＬ－ＩＮ－ＬＩＮＥ ＰＡＣＫＡＧＥ （０．３００ｉｎ．） ＭＩＮ Ａ ０．０１５ ｅＡ ｅＢ ＭＡＸ Ａ１ Ｃ Ｂ１ ＭＩＬＬＩＭＥＴＥＲＳ ＭＩＮ Ａ２ ０°－ １５° Ａ１ ＩＮＣＨＥＳ ＤＩＭ ＤＩＭ ＰＩＮ Ｄ ＩＮＣＨＥＳ ＭＩＬＬＩＭＥＴＥＲＳ ＭＩＮ ＭＡＸ ＭＩＮ ＭＡＸ ８ ０．３４８ ０．３９０ ８．８４ ９．９１ Ｄ １４ ０．７３５ ０．７６５ １８．６７ １９．４３ Ｄ １６ ０．７４５ ０．７６５ １８．９２ １９．４３ Ｄ １８ ０．８８５ ０．９１５ ２２．４８ ２３．２４ Ｄ ２０ １．０１５ １．０４５ ２５．７８ ２６．５４ Ｄ ２４ １．１４ １．２６５ ２８．９６ ３２．１３ Ｐａｇｅ ｏｆ １１ １１