PRELIMINARY TECHNICAL DATA High-Speed (10Mbps), Fail-Safe, RS-485/RS-422 Transceivers with Slew-Rate-Limiting and ±15kV ESD Protection ADM3082/ADM3085/ADM3088 a FEATURES Enhanced Slew Rate Limiting for Error-Free Data Transmission GENERAL DESCRIPTION The ADM3082/ADM3085/ADM3088 are high-speed RS-485/RS-422 transceivers consisting of one driver and one receiver per package. The devices feature fail-safe operation, ensuring a logic-high receiver output when the receiver inputs are open-circuit or short-circuit. This guarantees that the receiver output will be high if all the transmitters on a terminated bus are disabled (high-impedance). Fail-Safe Receiver Operation while Maintaining EIA/TIA-485 compatibility Low-Current (1nA) Shutdown Mode High Input Impedance — Up to 256 Transceivers on Bus ±15kV ESD Protection (Human Body Model) on RS-485 I/O pins The ADM3082 has a slew-rate limited driver to minimize electromagnetic interference (EMI) and reduce reflections caused by incorrectly terminated cables. This allows errorfree transmission at data rates up to 115kbps. Pin-Compatible with Industry Standard 75176 APPLICATIONS Enhanced Replacement for Industry-Standard Parts EMI-Sensitive Systems Level Translation LANs for Industrial Control Applications The ADM3085 offers a higher slew rate allowing data rates up to 500kbps, while the ADM3088 has a driver whose slew rate is not limited, allowing data rates up to 10Mbps. All devices in the family feature ±15kV electrostatic discharge (ESD) protection and high receiver input impedance (1/8 unit load), allowing up to 256 transceivers on the bus. The devices have low current drain of 375µA unloaded, or fully loaded with the drivers disabled, and feature an ultra-low power (1nA) shutdown mode. FUNCTIONAL BLOCK DIAGRAM RO 1 RE 2 DE 3 DI 4 8 VCC 7 B 6 A 5 G ND R D AD M 30 82/A D M 308 5/AD M 3088 REV. PrA 02/02 Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other rights of third parties which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices. One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. Tel: 617/329-4700 World Wide Web Site: http://www.analog.com Fax: 617/326-8703 © Analog Devices, Inc., 2002 PRELIMINARY TECHNICAL DATA ADM3082/ADM3085/ADM3088 ADM3082/ADM3085/ADM3088 SPECIFICATIONS 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) DRIVER Parameter Min Typ Differential Driver Output, V OD1 Differential Driver Output,VOD2 5 Driver Common-Mode Output Voltage, VOC Change-in-Magnitude of Common-Mode Voltage, DVOC Figure 1 (No Load) V V Figure 1, R = 50V (RS-422) Figure 1, R = 27V (RS-485) 0.2 V Figure 1, R = 50V or R = 27V (Note 2) 3 V Figure 1, R = 50V or R = 27V 0.2 V Figure 1, R = 50V or R = 27V (Note 2) 2.0 V Input Low Voltage, VlL1 (DE, DI, RE) 0.8 DI Input Hysteresis, VHYS Units Test Conditions/Comments V 2.0 1.5 Change-in-Magnitude of Differential Common-Mode Output Voltage, DV OD Input High Voltage,VIH1 (DE, DI, RE) Max 100 V mV Input Current, IIN1 (DE, DI, RE) ±2 µA Input Current (A and B), IIN4 125 µA –75 µA 125 µA Output Leakage (Y and Z), Full Duplex, IO Driver Short-Circuit,V OD1 DE VIN DE VIN = = = = GND, VCC = GND or 5.25V, 12V GND, VCC = GND or 5.25V, –7V DE VIN DE VIN = = = = GND, VCC = GND or 5.25V, 12V GND, VCC = GND or 5.25V, –7V –100 µA –250 mA –7V # VOUT # VCC (Note 3) mA mA 0V # VOUT # 12V (Note 3) 0V # VOUT # VCC (Note 3) Output Current 250 ±25 –2– REV. PrA 02/02 PRELIMINARY TECHNICAL DATA ADM3082/ADM3085/ADM3088 ADM3082/ADM3085/ADM3088 SPECIFICATIONS (continued) 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) RECEIVER Parameter Min Typ Max Receiver Differential Threshold Voltage, VTH –200 –125 –50 Receiver Input Hysteresis, DVTH Receiver Output High Voltage, VOH 25 Units Test Conditions/Comments mV –7V # VCM # 12V mV VCC –1 .5 V IO = -4mA, VID = -50mV Receiver Output Low Voltage, VOL 0.4 V IO = 4mA, VID = -200mV Three-State Output Current at Receiver, IOZR ±1 µA 0.4V # VO # 2.4V kV –7V # VCM # 12V mA 0V # VRO # VCC Receiver Input Resistance, RIN 96 Receiver Output Short-Circuit Current, IOSR ±7 ±95 SUPPLY CURRENT Parameter Supply Current, ICC Supply Current in Shutdown Mode, ISHDN ESD Protection for Y, Z, A, B Min Typ Max 430 900 µA 375 600 µA 0.001 10 µA DE = GND, VRE = VCC kV Human Body Model ±15 Units Test Conditions/Comments No DE No DE load, RE = DI = GND or VCC, = VCC load, RE = DI = GND or VCC, = GND NOTES 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. DDO and DVCC are the changes in VOD and VOC, respectively, when the DI input changes state. 3 Maximum current level applies to peak current just prior to foldback-current limiting; minimum current level applies during current limiting. 2 REV. PrA 02/02 –3– PRELIMINARY TECHNICAL DATA ADM3082/ADM3085/ADM3088 ADM3082/ADM3085/ADM3088 SPECIFICATIONS (continued) SWITCHING CHARACTERISTICS—ADM3082 (VCC = +5V ±5%, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = +5V and TA = +25°C.) (Note 1) Parameter Min Typ Max Driver Input-to-Output, tDPLH Driver Input-to-Output, tDPHL 500 500 2030 2030 2600 2600 ns ns Figures 2 and 3, RDIFF = 54V, CL1 = CL2 = 100pF –3 ±200 ns Figures 2 and 3, RDIFF = 54V, CL1 = CL2 = 100pF 1320 2500 ns Figures 2 and 3, RDIFF = 54V, CL1 = CL2 = 100pF Driver Output Skew,|tDPLH-tDPHL|, tDSKEW Driver Rise or Fall Time, tDR, tDF 667 Maximum Data Rate, fMAX 115 Units Test Conditions/Comments kbps Driver Enable to Output High, tDZH 3500 ns Figures 5 and 6, CL = 100pF, S2 closed Driver Enable to Output Low, tDZL 3500 ns Figures 5 and 6, CL = 100pF, S1 closed Driver Disable Time from Low, tDLZ 100 ns Figures 5 and 6, CL = l5pF, S1 closed Driver Disable Time from High, tDHZ 100 ns Figures 4 and 5, CL = l5pF, S2 closed 127 200 ns Figure 7; |VID| $ 2.0V; rise and fall time of VID # l5ns Differential Receiver Skew, tRSKD |tRPLH - tRPHL| 3 ±30 ns Figure 7; |VID| $ 2.0V; rise and fall time of VID # l5ns Receiver Enable to Output Low, tRZL 20 50 ns Figures 7 and 8; CL = 100pF, S1 closed Receiver Enable to Output High, tRZH 20 50 ns Figures 7 and 8, CL = 100pF, S2 closed Receiver Disable Time from Low, tRLZ 20 50 ns Figures 7 and 8, CL = 100pF, S1 closed Receiver Disable Time from High, tRHZ 20 50 ns Figures 7 and 8 CL = 100pF, S2 closed 200 600 ns (Note 5) Driver Enable from Shutdown to Output High, tDZH(SHDN) 6000 ns Figures 5 and 6, CL = l5pF, S2 closed Driver Enable from Shutdown to Output Low, tDZL(SHDN) 6000 ns Figures 5 and 6, CL = l5pF, S1 closed Receiver Enable from Shutdown to Output High, tRZH(SHDN) 3500 ns Figures 7 and 8, CL = 100pF, S2 closed Receiver Enable from Shutdown to Output Low, tRZL(SHDN) 3500 ns Figures 7 and 8, CL = 100pF, S1 closed Receiver Input to Output, tRPLH, tRPHL Time to Shutdown, tSHDN 50 –4– REV. PrA 02/02 PRELIMINARY TECHNICAL DATA ADM3082/ADM3085/ADM3088 ADM3082/ADM3085/ADM3088 SPECIFICATIONS (continued) SWITCHING CHARACTERISTICS—ADM3085 (VCC = +5V ±5%, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = +5V and TA = +25°C.) (Note 1) Parameter Min Typ Max Driver Input-to-Output, tDPLH Driver Input-to-Output, tDPHL 250 250 720 720 1000 1000 ns ns Figures 2 and 3 RDIFF = 54V, CL1 = CL2 = 100pF –3 ±100 ns Figures 2 and 3, RDIFF = 54V, CL1 = CL2 = 100pF 530 750 ns Figures 2 and 3, RDIFF = 54V, CL1 = CL2 = 100pF Driver Output Skew,|tDPLH - tDPHL|, tDSKEW Driver Rise or Fall Time, tDR, tDF 200 Maximum Data Rate, fMAX 500 Units Test Conditions/Comments kbps Driver Enable to Output High, tDZH 2500 ns Figures 5 and 6, CL = 100pF, S2 closed Driver Enable to Output Low, tDZL 2500 ns Figures 5 and 6, CL = 100pF, S1 closed Driver Disable Time from Low, tDLZ 100 ns Figures 5 and 6, CL = l5pF, S1 closed Driver Disable Time from High, tDHZ 100 ns Figures 5 and 6, CL = l5pF, S2 closed 127 200 ns Figure 7; |VID| $ 2.0V; rise and fall time of VID # l5ns Differential Receiver Skew, tRSKD |tRPLH - tRPHL| 3 ±30 ns Figure 7; |VID| $ 2.0V; rise and fall time of VID # l5ns Receiver Enable to Output Low, tRZL 20 50 ns Figures 7 and 8 CL = 100pF, S1 closed Receiver Enable to Output High, tRZH 20 50 ns Figures 7 and 8, CL = 100pF, S2 closed Receiver Disable Time from Low, tRLZ 20 50 ns Figures 7 and 8, CL = 100pF, S1 closed Receiver Disable Time from High, tRHZ 20 50 ns Figures 7 and 8, CL = 100pF, S2 closed 200 600 ns (Note 5) Driver Enable from Shutdown to Output High, tDZH(SHDN) 4500 ns Figures 5 and 6, CL = l5pF, S2 closed Driver Enable from Shutdown to Output Low, tOZL(SHDN) 4500 ns Figures 5 and 6, CL = l5pF, S1 closed Receiver Enable from Shutdown to Output High, tRZH(SHDN) 3500 ns Figures 7 and 8, CL = 100pF, S2 closed Receiver Enable from Shutdown to Output Low, tRZL(SHDN) 3500 ns Figures 7 and 8, CL = 100pF, S1 closed Receiver Input to Output, tRPLH, tRPHL Time to Shutdown, tSHDN REV. PrA 02/02 50 –5– PRELIMINARY TECHNICAL DATA ADM3082/ADM3085/ADM3088 ADM3082/ADM3085/ADM3088 SPECIFICATIONS (continued) SWITCHING CHARACTERISTICS—ADM3088 (VCC = +5V ±5%, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = +5V and TA = +25°C.) (Note 1) Parameter Min Driver Input-to-Output, tDPLH Driver Input-to-Output, tDPHL Driver Output Skew,|tDPLH -tDPHL|, tDSKEW Driver Rise or Fall Time, tDR, tDF Maximum Data Rate, fMAX Typ Max 34 34 60 60 ns ns Figures 2 and 5, RDIFF = 54V, CL1 = CL2 = 100pF –2.5 ±10 ns Figures 2 and 5, RDIFF = 54V, CL1 = CL2 = 100pF 14 25 ns Figures 7 and 9, RDIFF = 54V, CL1 = CL2 = 100pF 10 Units Test Conditions/Comments Mbps Driver Enable to Output High, tDZH 150 ns Figures 5 and 6, CL = 100pF, S2 closed Driver Enable to Output Low, tDZL 150 ns Figures 5 and 6, CL = 100pF, S1 closed Driver Disable Time from Low, tDLZ 100 ns Figures 5 and 6, CL = l5pF, S1 closed Driver Disable Time from High, tDHZ 100 ns Figures 5 and 6, CL = l5pF, S2 closed 106 150 ns Figure 7; |VID| $ 2.0V; rise and fall time of VID # l5ns DifferentialReceiver Skew, tRSKD |tRPLH – tRPHL| 0 ±10 ns Figures 7; |VID| $ 2.0V; rise and fall time of VID # l5ns Receiver Enable to Output Low, tRZL 20 50 ns Figures 7 and 8, CL = 100pF, S1 closed Receiver Enable to Output High, tRZH 20 50 ns Figures 7 and 8, CL = 100pF, S2 closed Receiver Disable Time from Low, tRLZ 20 50 ns Figures 7 and 8, CL = 100pF, S1 closed Receiver Disable Time from High, tRHZ 20 50 ns Figures 7 and 8, CL = 100pF, S2 closed 200 600 ns (Note 5) Driver Enable from Shutdown toOutput High, tDZH(SHDN) 250 ns Figures 5 and 6, CL = l5pF, S2 closed Driver Enable from Shutdown to Output Low, tDZL(SHDN) 250 ns Figures 5 and 6, CL = l5pF, S1 closed Receiver Enable from Shutdown to Output High, tRZH(SHDN) 3500 ns Figures 7 and 8, CL = 100pF, S2 closed Receiver Enable from Shutdown to Output Low, tRZL(SHDN) 3500 ns Figures 7 and 8, CL = 100pF, S1 closed Receiver Input-to-Output, tRPLH, tRPHL Time to Shutdown, tSHDN 50 NOTES The device is put into shutdown by bringing RE high and DE low. If the enable inputs are in this state for less than 50ns, the device is guaranteed not to enter shutdown. If the enable inputs are in this state for at least 600ns, the device is guaranteed to have entered shutdown. 5 –6– REV. PrA 02/02 PRELIMINARY TECHNICAL DATA ADM3082/ADM3085/ADM3088 ADM3082/ADM3085/ADM3088 TEST CIRCUITS AND TIMING VCC Y R VOD TEST P O INT R S1 Z VOC 500 V O UT P UT UN D E R TEST CR L S2 15p F Figure 1. Driver DC Load Test Circuit 3V Figure 5. Test Load for Driver Enable/Disable Time Test DE 5V CL 1 DE 1.5V DI VOD2 0V R D IFF tDL Z tDZL(S HD N) , t DZL CL2 Y, Z V OL 2.3V O U T PU T N O R M A LL Y HIG H Y, Z Figure 2. Test Load for Driver Timing Tests V OL V O L+0.5V O U T PU T N O R M A LL Y L O W V O H -0.5V 2.3V t DH Z t DZH (SH DN ) t DZH Figure 6. Driver Enable and Disable Times 5V DI 1.5V 0V tDP LH t DP H L VCC Z V0 Y V 0 /2 TEST P O INT V DIFF = V Y - V Z V DIFF V0 0 90% 90% 1k V 10% 10% -V 0 S1 t DR t DF t S KE W = |t DP LH -tDP H L | RO Figure 3. Driver Propagation Delays CRL 15p F S2 1k V A 1V B -1 V t RP HL VOH tRP LH Figure 7. Test Load for Receiver Enable/Disable Time Test 1 .5 V RO VOL Figure 4. Receiver Propagation Delays 5V RE 1.5V 0V V CC RO RO t RZ L (S HDN ) , t RZ L 1.5V 1.5V t RL Z V O L +0.5V O UT PU T NO R M A LL Y L O W O UT PU T NO R M A LL Y HIG H 0V t R ZH(S HD N) , t R ZH V O H -0.5V t R HZ Figure 8. Receiver Enable and Disable Delay Times REV. PrA 02/02 –7– PRELIMINARY TECHNICAL DATA ADM3082/ADM3085/ADM3088 PIN CONFIGURATION ABSOLUTE MAXIMUM RATINGS Supply Voltage (VCC) . . . . . . . . . . . . . . . . . . . . . . . . . . +7V Logic Input Voltage . . . . . . . . . . . . –0.3V to (V CC+0.3V) Driver Output Voltage (A, B) . . . . . . . . . . . . . . . . . . ±13V Receiver Input Voltage (A, B) . . . . . . . . . . . . . . . . . . ±13V Receiver Input Voltage, Full Duplex (A, B) . . . . . . ±13V Receiver Output Voltage (RO) . . . –0.3V to (V CC+0.3V) Continuous Power Dissipation 8-Pin Plastic DIP (derate 9.09mW/oC above +70oC) . . . . . . . . . . . 727mW 8-Pin Plastic SO (derate 5.88mW/oC above +70oC) . . . . . . . . . . . 471mW Maximum Junction Temperature (T J max) . . . . . . . 150 °C Storage Temperature Range . . . . . . . . . –65°C to +150°C Lead Temperature, Soldering Vapor Phase 60 sec . . . . . . . . . . . . . . . . . . . . . . . . . +215°C Infra-Red 15 sec . . . . . . . . . . . . . . . . . . . . . . . . . . . +200°C RO 1 RE 2 DE 3 DI 4 AD M 30 88/ AD M 30 85/ AD M 30 88 T O P V IE W (No t to S cale) ORDERING *Stresses above those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. This is a stress rating only; functional operation of the device at these or any other conditions above those indicated in the operational section of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. THERMAL CHARACTERISTICS 8-Pin Plastic DIP Package θJA = tbd K/Watt, θJC = tbd K/Watt 8-Pin Plastic SO Package θJA = tbd K/Watt, θJC = tbd K/Watt 8 VCC 7 B 6 A 5 G ND INFORMATION Model Temperature Range Package Option ADM3082JN 0°C to +70°C 8 Pin Plastic DIP ADM3082JR 0°C to +70°C 8 Pin SO ADM3082AN –40°C to +85°C 8 Pin Plastic DIP ADM3082AR –40°C to +85°C 8 Pin SO ADM3085JN 0°C to +70°C 8 Pin Plastic DIP ADM3085JR 0°C to +70°C 8 Pin SO ADM3085AN –40°C to +85°C 8 Pin Plastic DIP ADM3085AR –40°C to +85°C 8 Pin SO ADM3088JN 0°C to +70°C 8 Pin Plastic DIP ADM3088JR 0°C to +70°C 8 Pin SO ADM3088AN –40°C to +85°C 8 Pin Plastic DIP ADM3088AR 8 Pin SO –40°C to +85°C ADM3082/ADM3085/ADM3088TYPICALPERFORMANCECHARACTERISTICS AW AI TI NG D A AT TPC1. No-load Supply Current vs. Temperature AW A I IT NG T A D A AW TPC2. Output Current vs. Receiver Output High Voltage –8– AI N TI G T DA A TPC3. Output Current vs. Receiver Output Low Voltage REV. PrA 02/02 PRELIMINARY TECHNICAL DATA ADM3082/ADM3085/ADM3088 ADM3082/ADM3085/ADM3088 TYPICAL PERFORMANCE CHARACTERISTICS (continued) AW AI N TI G T DA A AW TPC4. Receiver Output High Voltage vs. Temperature AW AI TI NG D AW AI T DA AI N TI G T DA AW AI N TI G AI N TI G A TPC11. ADM3088 Receiver Propagation Delay vs. Temperature A T DA A TPC9. ADM3088 Driver Propagation Delay vs. Temperature AW –9– G A TPC8. ADM3085 Driver Propagation Delay vs. Temperature T DA AI N TI T DA TPC6. Shutdown Current vs. Temperature AW A TPC10. ADM3082/5 ReceIver Propagation Delay vs. Temperature REV. PrA 02/02 AW A AT TPC7. ADM3082 Driver Propagation Delay vs. Temperature G G A TPC5. Receiver Output Low Voltage vs. Temperature AW N TI AI N TI T DA AI N TI G T DA A TPC12. Driver Differential Output Voltage vs. Temperature PRELIMINARY TECHNICAL DATA ADM3082/ADM3085/ADM3088 ADM3082/ADM3085/ADM3088 TYPICAL PERFORMANCE CHARACTERISTICS (continued) AW A I IT NG T DA A AW TPC13. Driver Output Current vs. Differential Output Voltage AW AI TI NG D AI A AW A AT TPC16. ADM3082 Driver Propagation Delay I IT NG T A D G A TPC14. Output Current vs. Driver Output High Voltage AW AW N TI T DA A I IT NG T A D NG A TPC15. Output Current vs. Driver Output Low Voltage A AW TPC17. ADM3085 Driver Propagation Delay AW AI N TI G T DA A TPC18. ADM3088 Driver Propagation Delay A TPC19. ADM3082/5 Receiver Propagation Delay A I IT T DA A I IT NG T A D A TPC20. ADM3088 Receiver Propagation Delay –10– REV. PrA 02/02 PRELIMINARY TECHNICAL DATA ADM3082/ADM3085/ADM3088 PIN FUNCTION DESCRIPTION Pin Mnemonic Description 1 RO Receiver Output. When RE is low and A - B $ (more positive than) –50mV, RO will be high. When RE is low and A – B # (more negative than) –200mV, RO will be low. 2 RE Receiver Output Enable. Take RE low to enable RO; RO is high impedance when RE is high. Take RE high and DE low to enter low-power shutdown mode. 3 DE Driver Output Enable. Take DE high to enable driver outputs. These outputs are high impedance when DE is low. Take RE high and DE low to enter low-power shutdown mode. 4 DI Driver Input. With DE high, a low on DI forces non-inverting output low and inverting output high. Similarly, a high on DI forces non-inverting output high and inverting output low. 5 GND Ground 6 A Non-Inverting Receiver Input and Non-Inverting Driver Output 7 B Inverting Receiver Input and Inverting Driver Output 8 VCC Positive Supply 4.75V =V CC =5.25V DEVICE TRUTH TABLES RECEIVING TRANSMITTING INPUTS INPUTS OUTPUTS OUTPUT RE DE DI B/Z A/Y RE DE A-B RO X 1 1 0 1 0 X $ -0.05V 1 X 1 0 1 0 0 X # -0.2V 0 0 0 X High-Z High-Z 0 X Open/shorted 1 1 0 X 1 1 X High-Z 1 0 X Shutdown Shutdown X = Don’t care Shutdown mode, driver and receiver outputs high impedance REV. PrA 02/02 –11– PRELIMINARY TECHNICAL DATA ADM3082/ADM3085/ADM3088 DETAILED DESCRIPTION HIGH INPUT IMPEDANCE The ADM3082, ADM3085 and ADM3088 are highspeed RS-485/RS-422 transceivers offering enhanced performance over industry-standard devices All devices in the family contain one driver and one receiver, but there is a choice of performance options. The devices feature failsafe operation, which means that a logic-high receiver output is guaranteed when the receiver inputs are open-circuit or short-circuit, or when they are connected to a terminated transmission line with all drivers disabled (see the section on Fail-Safe Operation). The input impedance of the devices is 96kV, which is 8 times higher than the standard RS-485 load of 12kV. A standard driver can driver 32 standard loads, so up to 256 ADM308X receivers, or a combination of ADM308X and other devices up to 32 unit loads, may be connected to an RS-422/RS485 bus driven by a single driver. SLEW RATE CONTROL If shutdown mode is not used, the fact that DE is activehigh and RE is active-low offers a convenient way of switching the device between transmit and receive, by tying DE and RE together. This is useful, for example, in applications using half duplex operation and where several receiver outputs are connected to a serial bus. The ADM3082 features a controlled slew-rate driver that minimize electromagnetic interference (EMI) and reduce reflections caused by incorrectly terminated cables, allowing error-free data transmission rates up to 115kbps (see the section on Reduced EMI and Reflections). SHUTDOWN MODE All the devices have a low power shutdown mode that is enabled by taking RE high and DE low. The driver slew rate of the ADM3088 is not limited, offering data transmission rates up to 10Mbps. The device is guaranteed not to enter shutdown mode if DE and RE are driven in this way. If DE is low and RE is high for less than 50ns the device will not enter shutdown. If DE is low and RE is high for greater than 600ns, the device is guaranteed to enter shutdown. RECEIVER INPUT FILTERING FAIL-SAFE OPERATION The ADM3085 offers a higher limit on driver output slew-rate, allowing data transmission rates up to 500kbps. The receivers of all devices incorporate input hysteresis. In addition, when operating in 115kbps or 500kbps mode, the receivers of the ADM3082 and ADM3085 incorporate input filtering. This enhances noise immunity with differential signals that have very slow rise and fall times, but it does increase propagation delay by 20%. HALF-/FULL-DUPLEX OPERATION The ADM3082, ADM3085, and ADM3088 are dedicated half-duplex devices (driver outputs internally linked to receiver inputs). Figure 29 shows a typical half-duplex connection between two devices. THREE-STATE BUS CONNECTION All the devices have a Driver Enable pin (DE) that enables the driver outputs when taken high or puts the driver outputs into a high-impedance state when taken low. This allows several driver outputs to be connected to an RS-422/RS-485 bus. Similarly, all the devices have a (active-low) Receiver Enable pin (RE). Taking this low enables the receiver, while taking it high puts the receiver outputs into a high-impedance state. This allows several receiver outputs to be connected to a serial data bus. RE C E IV E R O UT P UT (RO ) 100n 1 ENHANCED ESD PROTECTION All Analog Devices parts incorporate protection against electrostatic discharge (ESD) to protect the devices during handling, assembly and normal operation. In addition, the ADM308X family has enhanced ESD protection up to ±15kV on the receiver inputs and driver outputs (A, B) to protect against severe operational conditions such as line transients, connection and disconnection. +5V (V C C ) 5 8 D 4 DA T A IN (D I) 3 DR IV E R E NA BL E (DE ) 2 RE C E IV E R E NA BL E (R E ) 1 RE C E IV E R O UT P UT (RO ) R RE C E IV E R E NA BL E (R E ) 2 DR IV E R E NA BL E (DE ) 3 DA T A IN (D I) The ADM3082/ADM3085/ADM3088 offer true fail-safe operation while remaining fully compliant with the ±200mV EIA/TIA-485 standard. A logic-high receiver output is guaranteed when the receiver inputs are shorted together or open-circuit, or when they are connected to a terminated transmission line with all drivers disabled. This is done by setting the receiver threshold between -50mV 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 ADM308X family, which results in a logic high with a 50mV minimum noise margin. 6 7 RT RT 4 7 6 D 5 +5V (V C C ) R 8 100n AD M 308 2/5/8 AD M 308 2/5/8 Figure 29. Half-Duplex Configuration for ADM3082, ADM3085 or ADM3088 –12– REV. PrA 02/02 PRELIMINARY TECHNICAL DATA ADM3082/ADM3085/ADM3088 CURRENT LIMIT AND THERMAL SHUTDOWN The ADM3082/ADM3085/ADM3088 incorporate two protection mechanisms to guard the drivers against shortcircuits, bus contention or other fault conditions. The first is a foldback current-limited output stage that protects the driver against short-circuits over the entire common-mode voltage range. The second is a thermal shutdown circuit that puts the driver outputs into a high-impedance state if the die temperature exceeds a safe limit. AW REDUCED EMI AND REFLECTIONS The ADM3082 and ADM3085 incorporate slew-rating limiting in the drivers. This reduces reflections due to incorrect cable termination and minimizes electromagnetic interference (EMI). Figures 9 to 11 show driver output waveforms and Fourier analyses of 20kHz signals for the three different slew-rate settings. It can be seen that the harmonic content is greatly reduced for the ADM3085 and still further for the ADM3082 (Figures 10 and 9 respectively). A I IT NG T DA A Figure 11. ADM3088 Driver Output Waveform and FFT Plot The length of an unterminated stub that can be driven with only minor reflections depends on the rise time of the transmitter. A conservative estimate for this is given by the following equation: L (metres) = tR / 49.2 where tR is the transmitter’s rise time in ns (multiply result by 3.28 for answer in feet). AW AI N TI G T DA For example, the rise time of the ADM3082 is typically 1320ns, which results in acceptable waveforms with stub lengths up to 27 metres. This is not the ultimate limit on unterminated stub length, as a system can still work if the waveformis allowed to settle before sampling the data. A The RS-485/RS-422 standard covers line lengths up to 4000 feet (1219 metres). Driver output and receiver output waveforms for the three slew rate settings, driving a 4000 foot cable, are shown in figures 12 to 14. Figure 9 ADM3082 Driver Output Waveform and FFT Plot AW AI N TI G DA TA AW NG A Figure 12. Driver Input, Driver Output and Receiver Output Waveforms of ADM3082, Driving 4000ft (1219m) of Cable at 50kHz Figure 10. ADM3085 Driver Output Waveform and FFT Plot REV. PrA 02/02 A I IT T DA –13– PRELIMINARY TECHNICAL DATA ADM3082/ADM3085/ADM3088 APPLICATIONS T AI AW I NG T A D Figures 15 shows a typical application of the device on a half--duplex network. The line should be terminated at both ends to minimize reflections and any stubs off the main line should be kept as short as possible. A 120 V R RO RE DE A DI Figure 13. Driver Input, Driver Output and Receiver Output Waveforms of ADM3085, Driving 4000ft (1219m) of Cable at 50kHz D R RO RE DE AI AW TI NG D D R RO RE DE D R RO RE DE B A DI D 120 V AD M 3082, ADM 3084, AD M 308 5 O R AD M 3089 W IT H H /F = V C C Figure 15. Typical Half-Duplex Network Application For line lengths in excess of 1220 metres the line should be split into smaller sections with intermediate repeaters. OUTLINE B A DI Figure 14. Driver Input, Driver Output and Receiver Output Waveforms of ADM3088, Driving 4000ft (1219m) of Cable at 200kHz B A DI A AT B DIMENSIONS Dimensions shown in inches and (mm). 8-Pin Plastic Dual-In-Line Package (N-8) 8-Pin SO Package (R-8) 0.43 0 (10 .92 ) 0.19 6 8 (5 . 00) 0.34 8 (8.84 ) 8 0.18 9 0 (4 . 80) 5 0. 280 (7.11 ) 85 0. 240 (6.10 ) 14 0. 325 (8.25 ) P IN 1 0. 060 (1.52 ) 0. 015 (0.38 ) 0.21 0 (5.33 ) MAX 0.16 0 (4.06 ) 0.11 5 (2.93 ) 0.02 2 (0.5 58 ) 0.1 0 0 0.07 0 (1.77 ) 0.01 4 (0.3 56 ) (2 .54 ) 0.04 5 (1.15 ) BSC 0.1 3 0 (3 .30 ) M IN S E A T IN G PLANE 0.15 7 4 (4 .00 ) 0. 244 0 (6. 20 ) 0. 228 4 (5. 80 ) 0. 300 (7.62 ) 1 4 0.14 9 7 (3 .80 ) 0.19 5 (4. 95) 0.11 5 (2. 93) P IN 1 0. 015 (0.3 81 ) 0. 102 (2.59) 0.01 9 6 (0 . 50) 0. 094 (2.39) 0.00 9 9 (0 . 25) x 45 0.009 8 (0. 25 ) 0. 008 (0.2 04 ) 0.004 0 (0. 10 ) SE A TIN G PLANE –14– 0.0 5 00 (1 .27 ) BS C 0.01 9 2 (0 . 49) 0.01 3 8 (0 . 35) 0.00 9 8 (0 . 25) 0.00 7 5 (0 . 19) 8 0 0.05 0 0 (1 .27 ) 0.01 6 0 (0 .41 ) REV. PrA 02/02