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| a FEATURES Operates with +3.3 V Supply EIA RS-422 and RS-485 Compliant Over Full CM Range 19 k Input Impedance Up to 50 Transceivers on Bus 20 Mbps Data Rate Short Circuit Protection Specified Over Full Temperature Range Thermal Shutdown Interoperable with 5 V Logic 840 A Supply Current 2 nA Shutdown Current Also Available in TSSOP Package Meets IEC1000-4-4 (>1 kV) 8 ns Skew Upgrade for MAX 3491, SN75ALS180 APPLICATIONS Telecommunications DTE-DCE Interface Packet Switching Local Area Networks Data Concentration Data Multiplexers Integrated Services Digital Network (ISDN) AppleTalk Industrial Controls 3.3 V, Full Duplex, 840 A 20 Mbps, EIA RS-485 Transceiver ADM3491 FUNCTIONAL BLOCK DIAGRAM ADM3491 A RO RE DE Z DI D Y R B The receiver contains a fail-safe feature that results in a logic high output state if the inputs are unconnected (floating). The ADM3491 is fabricated on BiCMOS, an advanced mixed technology process combining low power CMOS with fast switching bipolar technology. The ADM3491 is fully specified over the industrial temperature range and is available in DIP and SOIC packages as well as a new space saving TSSOP package. GENERAL DESCRIPTION The ADM3491 is a low power differential line transceiver designed to operate using a single +3.3 V power supply. Low power consumption coupled with a shutdown mode make it ideal for power sensitive applications. It is suitable for communication on multipoint bus transmission lines. It is intended for balanced data transmission and complies with both EIA Standards RS-485 and RS-422. It contains a differential line driver and a differential line receiver, making it suitable for full duplex data transfer. The input impedance is 19 k allowing up to 50 transceivers to be connected on the bus. Excessive power dissipation caused by bus contention or by output shorting is prevented by a thermal shutdown circuit. This feature forces the driver output into a high impedance state if, during fault conditions, a significant temperature increase is detected in the internal driver circuitry. REV. 0 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: 781/329-4700 World Wide Web Site: http://www.analog.com Fax: 781/326-8703 (c) Analog Devices, Inc., 1998 ADM3491-SPECIFICATIONS (V Parameter DRIVER Differential Output Voltage, VOD |VOD| for Complementary Output States Common-Mode Output Voltage VOC |VOC| for Complementary Output States CMOS Input Logic Threshold Low, VINL CMOS Input Logic Threshold High, VINH Logic Input Current (DE, DI, RE) Output Leakage (Y, Z) Current Output Short Circuit Current RECEIVER Differential Input Threshold Voltage, VTH Input Voltage Hysteresis, VTH Input Resistance Input Current (A, B) Logic Enable Input Current (RE) Output Voltage Low, VOL Output Voltage High, VOH Short Circuit Output Current Three-State Output Leakage Current POWER SUPPLY CURRENT ICC Supply Current in Shutdown Specifications subject to change without notice. CC = +3.3 V Typ 0.3 V. All specifications TMIN to TMAX unless otherwise noted.) Max Units V V V V V V V V A A mA V mV k mA mA A V V mA A Test Conditions/Comments RL = 100 , Figure 1, VCC > 3.1 V RL = 54 , Figure 1 RL = 60 , Figure 2, -7 V < VTST < +12 V R = 54 or 100 , Figure 1 R = 54 or 100 , Figure 1 R = 54 or 100 , Figure 1 Min 2.0 1.5 1.5 0.2 3 0.2 0.8 2.0 1.0 3 250 +0.2 50 19 +1 -0.8 1 0.4 VCC -0.4 V 60 1.0 VO = -7 V or +12 V, VCC = 0 V or 3.6 V VO = -7 V or +12 V -7 V < VCM < +12 V VCM = 0 V -7 V < VCM < +12 V VIN = +12 V VIN = -7 V IOUT = +2.5 mA IOUT = -1.5 mA VOUT = GND or VCC VCC = 3.6 V, 0 V < VOUT < VCC Outputs Unloaded, DE = VCC, RE = 0 V DE = 0 V, RE = 0 V DE = 0 V, RE = VCC -0.2 12 0.84 0.84 0.002 1.2 1.2 1 mA mA A -2- REV. 0 ADM3491 TIMING SPECIFICATIONS (V Parameter DRIVER Differential Output Delay TDD Differential Output Transition Time Propagation Delay Input to Output TPLH, TPHL Driver O/P to O/P TSKEW ENABLE/DISABLE Driver Enable to Output Valid Driver Disable Timing Driver Enable from Shutdown RECEIVER Time to Shutdown Propagation Delay Input to Output TPLH, TPHL Skew TPLH-TPHL Receiver Enable TEN Receiver Disable TDEN Receiver Enable from Shutdown 80 25 CC = +3.3 V, TA = +25 C) Min 1 1 7 Typ Max 35 15 35 8 90 80 110 300 90 10 50 45 500 Units ns ns ns ns ns ns ns ns ns ns ns ns ns Test Conditions/ Comments RL = 60 , CL1 = CL2 = 15 pF, Figure 5 RL = 60 , CL1 = CL2 = 15 pF, Figure 5 RL = 27 , CL1 = CL2 = 15 pF, Figure 6 RL = 54 , CL1 = CL2 = 15 pF, Figure 6 RL = 110 , CL = 50 pF, Figure 3 RL = 110 , CL = 50 pF, Figure 3 RL = 110 , CL = 15 pF, Figure 3 8 22 45 40 650 190 65 25 25 CL = 15 pF, Figure 8 CL = 15 pF, Figure 8 CL = 15 pF, Figure 4 CL = 15 pF, Figure 4 CL = 15 pF, Figure 4 TIMING SPECIFICATIONS (V Parameter CC = +3.3 V 0.3 V, TA = TMIN to TMAX) Min 1 2 7 Typ Max 70 15 70 10 110 110 110 500 115 20 50 50 600 Units ns ns ns ns ns ns ns ns ns ns ns ns ns Test Conditions/ Comments RL = 60 , CL1 = CL2 = 15 pF, Figure 5 RL = 60 , CL1 = CL2 = 15 pF, Figure 5 RL = 27 , CL1 = CL2 = 15 pF, Figure 6 RL = 54 , CL1 = CL2 = 15 pF, Figure 6 RL = 110 , CL = 50 pF, Figure 3 RL = 110 , CL = 50 pF, Figure 3 RL = 110 , CL = 15 pF, Figure 3 DRIVER Differential Output Delay TDD Differential Output Transition Time Propagation Delay Input to Output TPLH, TPHL Driver O/P to O/P TSKEW ENABLE/DISABLE Driver Enable to Output Valid Driver Disable Timing Driver Enable from Shutdown RECEIVER Time to Shutdown Propagation Delay Input to Output TPLH, TPHL Skew TPLH-TPHL Receiver Enable TEN Receiver Disable TDEN Receiver Enable from Shutdown 8 22 45 40 650 50 25 190 65 25 25 CL = 15 pF, Figure 8 CL = 15 pF, Figure 8 CL = 15 pF, Figure 4 CL = 15 pF, Figure 4 CL = 15 pF, Figure 4 REV. 0 -3- ADM3491 ABSOLUTE MAXIMUM RATINGS* (TA = +25C unless otherwise noted) VCC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +7 V Inputs Driver Input (DI) . . . . . . . . . . . . . . . .-0.3 V to VCC + 0.3 V Control Inputs (DE, RE) . . . . . . . . . .-0.3 V to VCC + 0.3 V Receiver Inputs (A, B) . . . . . . . . . . . . . . . -7.5 V to +12.5 V Outputs Driver Outputs . . . . . . . . . . . . . . . . . . . . . -7.5 V to +12.5 V Receiver Output . . . . . . . . . . . . . . . . . -0.5 V to VCC +0.5 V Power Dissipation 14-Lead DIP . . . . . . . . . . . . . . . . 800 mW JA, Thermal Impedance . . . . . . . . . . . . . . . . . . . 140C/W Power Dissipation 14-Lead SOIC . . . . . . . . . . . . . . . 650 mW JA, Thermal Impedance . . . . . . . . . . . . . . . . . . . 115C/W Power Dissipation 16-Lead TSSOP . . . . . . . . . . . . . . 500 mW JA, Thermal Impedance . . . . . . . . . . . . . . . . . . . 158 C/W Operating Temperature Range Industrial (A Version) . . . . . . . . . . . . . . . . -40C to +85C Storage Temperature Range . . . . . . . . . . . . -65C to +150C Lead Temperature (Soldering, 10 sec) . . . . . . . . . . . . +300C Vapor Phase (60 sec) . . . . . . . . . . . . . . . . . . . . . . . . +215C Infrared (15 sec) . . . . . . . . . . . . . . . . . . . . . . . . . . .+220C ESD Rating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . >2 kV EFT Rating (IEC1000-4-4) . . . . . . . . . . . . . . . . . . . . . . >1 kV *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 listed in the operational sections of this specification is not implied. Exposure to absolute maximum ratings for extended periods of time may affect device reliability. ORDERING GUIDE Model ADM3491AN ADM3491AR ADM3491ARU Temperature Range -40C to +85C -40C to +85C -40C to +85C Package Description Plastic DIP Small Outline (SOIC) Thin Shrink Small Outline (TSSOP) Package Options N-14 R-14 RU-16 -4- REV. 0 ADM3491 PIN CONFIGURATION DIP/SOIC NC 1 RO 2 RE 3 14 VCC VCC ADM3491 13 12 A TOP VIEW DE 4 (Not to Scale) 11 B DI 5 GND 6 GND 7 10 9 8 Z Y NC NC = NO CONNECT TSSOP VCC 1 NC 2 RO 3 RE 4 16 15 NC A B ADM3491 14 13 NC TOP VIEW DE 5 (Not to Scale) 12 Z DI 6 11 10 9 Y NC NC NC 7 GND 8 NC = NO CONNECT PIN FUNCTION DESCRIPTIONS Mnemonic Pin NC RO RE DIP/ SOIC 1, 8 2 3 TSSOP 2, 7, 9, 10, 13, 16 3 4 Function No Connect. Receiver Output. High when A > B by 200 mV or Low when A < B by 200 mV. Receiver Output Enable. With RE low, the receiver output RO is enabled. With RE high, the output goes high impedance. If RE is high and DE low, the ADM3491 enters a shutdown state. Driver Output Enable. A high level enables the driver differential outputs, Y and Z. A low level places it in a high impedance state. Driver Input. When the driver is enabled, a logic Low on DI forces Y low and Z high while a logic high on DI forces Y high and Z low. Ground Connection, 0 V. Noninverting Driver Output Y. Inverting Driver Output Z. Inverting Receiver Input B. Noninverting Receiver Input A. Power Supply, 3.3 V 0.3 V. DE DI GND Y Z B A VCC 4 5 6, 7 9 10 11 12 13, 14 5 6 8 11 12 14 15 1 REV. 0 -5- ADM3491 Test Circuits R/2 VOD R/2 VCC 375 VOD3 RL VTST 375 VOC Figure 1. Driver Voltage Measurement Test Circuit VCC RL CL VOUT Figure 5. Driver Voltage Measurement Test Circuit 2 +1.5V S1 -1.5V RE IN RE RL CL VOUT VCC 0V OR 3V DE S1 S2 S2 DE IN Figure 2. Driver Enable/Disable Test Circuit Figure 6. Receiver Enable/Disable Test Circuit VOM DI CL1 D RLDIFF VOUT CL2 IN DE S1 CL VCC RL VOUT Figure 3. Driver Differential Output Delay Test Circuit Figure 7. Driver Propagation Delay Test Circuit 3V DI CL1 D RLDIFF CL2 A B R RE RO 0V VID +1.5V RE CL VOUT Figure 4. Driver/Receiver Propagation Delay Test Circuit Figure 8. Receiver Propagation Delay Test Circuit -6- REV. 0 ADM3491 Switching Characteristics 3V 1.5V 0V Z VO R Y 1.5V RE 1.5V 1.5V 0V 3V tPLH 1/2VO tPHL tZL 1.5V tLZ O/P LOW VOL + 0.25V VOL tSKEW VO 0V -VO 10% POINT 90% POINT tSKEW 90% POINT 10% POINT R 0V tZH O/P HIGH 1.5V tHZ VOH VOH - 0.25V tR tF Figure 9. Driver Propagation Delay, Rise/Fall Timing Figure 11. Driver Enable/Disable Timing 3V RE 1.5V 1.5V 0V A-B 0V 0V tZL R VOH tLZ 1.5V O/P LOW t PLH t PHL VOL + 0.25V VOL tZH 1.5V RO VOL 1.5V tHZ O/P HIGH VOH VOH - 0.25V R 0V 1.5V Figure 10. Receiver Propagation Delay Figure 12. Receiver Enable/Disable Timing REV. 0 -7- ADM3491-Typical Performance Characteristics 14 12 14 12 OUTPUT CURRENT - mA 10 8 OUTPUT CURRENT - mA 10 8 6 6 4 2 0 4 2 0 0 0.5 1 1.5 2 2.5 3 3.5 0 0 .5 1 1.5 2 2.5 3 3.5 4 OUTPUT VOLTAGE - Volts OUTPUT HIGH VOLTAGE - Volts Figure 13. Receiver Output Low Voltage vs. Output Current Figure 16. Receiver Output High Voltage vs. Output Current 0.8 0.7 3.3 3.25 OUTPUT VOLTAGE - V OUTPUT VOLTAGE - V 0.6 0.5 0.4 0.3 0.2 IRO = 2.5mA 3.2 IRO = -1.5mA 3.15 3.1 3.05 0.1 0 -40 -20 0 20 40 60 80 100 3 -40 -20 0 20 40 60 80 100 TEMPERATURE - C TEMPERATURE - C Figure 14. Receiver Output Low Voltage vs. Temperature Figure 17. Receiver Output High Voltage vs. Temperature 120 2.6 2.5 100 2.4 OUTPUT CURRENT - mA OUTPUT VOLTAGE - V 80 2.3 2.2 2.1 2.0 1.9 1.8 1.7 60 40 20 0 0 0.5 1 1.5 2 2.5 DIFFERENTIAL O/P VOLTAGE - Volts 3 1.6 -40 -20 0 20 40 60 80 100 TEMPERATURE - C Figure 15. Driver Differential Output Voltage vs. Output Current Figure 18. Driver Differential Output Voltage vs. Temperature -8- REV. 0 ADM3491 1.2 [ T ] T 3 T 100FT CAT 5 CABLE 1.1 SUPPLY CURRENT - mA 1 0.9 T 1 2 0.8 4 T 0.7 -40 -20 0 20 40 60 80 100 TEMPERATURE - C CH1 1.00V CH3 2.00V CH2 1.00V CH4 2.00V M40.0ns CH3 640mV Figure 19. Supply Current vs. Temperature Figure 21. Driving 100 ft. Cable H-L Transition [ T ] 100 90 3 T T 100FT CABLE SHUTDOWN CURRENT - mA 80 70 60 50 40 30 20 1 2 T T 4 10 CH1 1.00V CH3 2.00V CH2 1.00V CH4 2.00V M40.0ns CH3 640mV 0 -40 -20 0 20 40 TEMPERATURE - C 60 80 Figure 20. Driving 100 ft. Cable L-H Transition Figure 22. Shutdown Current vs. Temperature REV. 0 -9- ADM3491 +3.3V 0.1 F +3.3V 0.1 F RE RO VCC A R B Y VCC DE DI Z D ADM3491 Z DI D DE GND Y RS-485/RS-422 LINK B A ADM3491 RO R RE GND Figure 23. ADM3491 Full-Duplex Data Link Table I. Transmitting Truth Table Transmitting Inputs RE X X 0 1 DE 1 1 0 0 DI 1 0 X X Z 0 1 Hi-Z Hi-Z Outputs Y 1 0 Hi-Z Hi-Z Table II. Receiving Truth Table Receiving Inputs RE 0 0 0 1 DE X X X X A-B > +0.2 V < -0.2 V Inputs O/C X Outputs RO 1 0 1 Hi-Z -10- REV. 0 ADM3491 APPLICATIONS INFORMATION Differential Data Transmission Cable and Data Rate Differential data transmission is used to reliably transmit data at high rates over long distances and through noisy environments. Differential transmission nullifies the effects of ground shifts and noise signals which appear as common-mode voltages on the line. Two main standards are approved by the Electronics Industries Association (EIA) which specify the electrical characteristics of transceivers used in differential data transmission. The RS-422 standard specifies data rates up to 10 MBaud and line lengths up to 4000 ft. A single driver can drive a transmission line with up to 10 receivers. The RS-485 standard was defined to cater to true multipoint communications. This standard meets or exceeds all the requirements of RS-422, but also allows multiple drivers and receivers to be connected to a single bus. An extended common mode range of -7 V to +12 V is defined. The most significant difference between RS-422 and RS-485 is the fact that the drivers may be disabled thereby allowing more than one to be connected to a single line. Only one driver should be enabled at a time, but the RS-485 standard contains additional specifications to guarantee device safety in the event of line contention. The transmission line of choice for RS-485 communications is a twisted pair. Twisted pair cable tends to cancel common-mode noise and also causes cancellation of the magnetic fields generated by the current flowing through each wire, thereby reducing the effective inductance of the pair. The ADM3491 is designed for bidirectional data communications on multipoint transmission lines. A typical application showing a multipoint transmission network is illustrated in Figure 23. Only one driver can transmit at a particular time, but multiple receivers may be enabled simultaneously. As with any transmission line, it is important that reflections are minimized. This may be achieved by terminating the extreme ends of the line using resistors equal to the characteristic impedance of the line. Stub lengths of the main line should also be kept as short as possible. A properly terminated transmission line appears purely resistive to the driver. Receiver Open-Circuit Fail Safe The receiver input includes a fail-safe feature that guarantees a logic high on the receiver when the inputs are open circuit or floating. Table III. Comparison of RS-422 and RS-485 Interface Standards Specification Transmission Type Maximum Cable Length Minimum Driver Output Voltage Driver Load Impedance Receiver Input Resistance Receiver Input Sensitivity Receiver Input Voltage Range RS-422 Differential 4000 ft. 2 V 100 4 k min 200 mV -7 V to +7 V RS-485 Differential 4000 ft. 1.5 V 54 12 k min 200 mV -7 V to +12 V REV. 0 -11- ADM3491 OUTLINE DIMENSIONS Dimensions shown in inches and (mm). 14-Lead Plastic DIP (N-14) 0.795 (20.19) 0.725 (18.42) 14 1 8 7 14-Lead Narrow Body Small Outline (SOIC) (R-14) 0.3444 (8.75) 0.3367 (8.55) 0.280 (7.11) 0.240 (6.10) 0.060 (1.52) 0.015 (0.38) 0.130 (3.30) MIN PIN 1 0.210 (5.33) MAX 0.160 (4.06) 0.115 (2.93) 0.022 (0.558) 0.014 (0.356) 0.325 (8.25) 0.300 (7.62) 0.195 (4.95) 0.115 (2.93) 0.1574 (4.00) 0.1497 (3.80) 14 1 8 7 0.2440 (6.20) 0.2284 (5.80) PIN 1 0.0098 (0.25) 0.0040 (0.10) 0.0688 (1.75) 0.0532 (1.35) 0.0196 (0.50) x 45 0.0099 (0.25) 0.100 0.070 (1.77) (2.54) 0.045 (1.15) BSC SEATING PLANE 0.015 (0.381) 0.008 (0.204) SEATING PLANE 0.0500 (1.27) BSC 0.0192 (0.49) 0.0138 (0.35) 0.0099 (0.25) 0.0075 (0.19) 8 0 0.0500 (1.27) 0.0160 (0.41) 16-Lead Thin Shrink Small Outline (TSSOP) (RU-16) 0.201 (5.10) 0.193 (4.90) 16 9 0.177 (4.50) 0.169 (4.30) 1 8 PIN 1 0.006 (0.15) 0.002 (0.05) 0.0433 (1.10) MAX 0.0256 (0.65) BSC 0.0118 (0.30) 0.0075 (0.19) 0.0079 (0.20) 0.0035 (0.090) 0.256 (6.50) 0.246 (6.25) SEATING PLANE 8 0 0.028 (0.70) 0.020 (0.50) -12- REV. 0 PRINTED IN U.S.A. C3216-8-1/98 |
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