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| a FEATURES Meets and Exceeds EIA RS-485 and EIA RS-422 Standards 30 Mbps Data Rate Recommended for PROFIBUS Applications 2.1 V Minimum Differential Output with 54 Termination Low Power 0.8 mA ICC Thermal Shutdown and Short Circuit Protection 0.5 ns Skew Driver and Receiver Driver Propagation Delay: 11 ns Receiver Propagation Delay: 12 ns High Impedance Outputs with Drivers Disabled or Power Off Superior Upgrade for SN65ALS1176 Available in Standard 8-Lead SOIC Package APPLICATIONS Industrial Field Equipment RO 5 V, 0.8 mA PROFIBUS RS-485 Transceiver ADM1486 FUNCTIONAL BLOCK DIAGRAM ADM1486 R VCC RE B DE A DI D GND GENERAL DESCRIPTION The ADM1486 is a differential line transceiver suitable for high speed bidirectional data communication on multipoint bus transmission lines. It is designed for balanced data transmission, complies with EIA Standards RS-485 and RS-422, and is recommended for PROFIBUS applications. The part contains a differential line driver and a differential line receiver. Both the driver and the receiver may be enabled independently. When disabled or with power off, the driver outputs are high impedance. The ADM1486 operates from a single 5 V power supply. Excessive power dissipation caused by bus contention or by output shorting is prevented by short circuit protection and thermal circuitry. Short circuit protection circuits limit the maximum output current to 200 mA during fault conditions. A thermal shutdown circuit senses if the die temperature rises above 150C and forces the driver outputs into a high impedance state under this condition. Up to 50 transceivers may be connected simultaneously on a bus, but only one driver should be enabled at any time. It is therefore important that the remaining disabled drivers do not load the bus. To ensure this, the ADM1486 driver features high output impedance when disabled and when powered down. This minimizes the loading effect when the transceiver is not being used. The high impedance driver output is maintained over the entire common-mode voltage range from -7 V to +12 V. The receiver contains a fail-safe feature that results in a logic high output state if the inputs are unconnected (floating). The ADM1486 is fabricated on BiCMOS, an advanced mixed technology process combining low power CMOS with fast switching bipolar technology. All inputs and outputs contain protection against ESD; all driver outputs feature high source and sink current capability. An epitaxial layer is used to guard against latch-up. The ADM1486 features extremely fast and closely matched switching, enable, and disable times. Minimal driver propagation delays permit transmission at data rates up to 30 Mbps while low skew minimizes EMI interference. The part is fully specified over the commercial and industrial temperature range and is available in an 8-lead SOIC package. 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 that 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 www.analog.com Fax: 781/326-8703 (c) Analog Devices, Inc., 2002 ADM1486-SPECIFICATIONS (V Parameter DRIVER Differential Output Voltage, VOD VOD3 |VOD| for Complementary Output States Common-Mode Output Voltage VOC |VOC| for Complementary Output States Output Short Circuit Current (VOUT = High) Output Short Circuit Current (VOUT = Low) CMOS Input Logic Threshold Low, VINL CMOS Input Logic Threshold High, VINH Logic Input Current (DE, DI) RECEIVER Differential Input Threshold Voltage, VTH Input Voltage Hysteresis, VTH Input Resistance Input Current (A, B) Logic Enable Input Current (RE) CMOS Output Voltage Low, VOL CMOS Output Voltage High, VOH Short Circuit Output Current Three-State Output Leakage Current POWER SUPPLY CURRENT ICC (Outputs Enabled) ICC (Outputs Disabled) Specifications subject to change without notice. CC =5V 5%. All specifications TMIN to TMAX, unless otherwise noted.) Unit V V V V V V V mA mA V V A V mV k mA mA A V V mA A mA mA Test Conditions/Comments R = Infinity, Test Circuit 1 VCC = 5 V, R = 50 (RS-422), Test Circuit 1 R = 27 (RS-485), Test Circuit 1 VTST = -7 V to +12 V, Test Circuit 2 R = 27 or 50 , Test Circuit 1 R = 27 or 50 , Test Circuit 1 R = 27 or 50 -7 V VO +12 V -7 V VO +12 V Min Typ Max 5.0 5.0 5.0 5.0 0.2 3 0.2 200 200 0.8 1.0 2.1 2.1 2.1 60 60 2.0 -0.2 20 70 30 +0.2 0.6 -0.35 1 0.4 4.0 7 85 1.0 1.2 0.8 2 1.5 -7 V VCM +12 V VCM = 0 V -7 V VCM +12 V VIN = +12 V VIN = -7 V IOUT = +4.0 mA IOUT = -4.0 mA VOUT = GND or VCC 0.4 V VOUT 2.4 V Outputs Unloaded, Digital Inputs = GND or VCC Outputs Unloaded, Digital Inputs = GND or VCC TIMING SPECIFICATIONS Parameter (VCC = 5 V 5%. All specifications TMIN to TMAX, unless otherwise noted.) Min 4 Typ 11 11 0.5 8 9 9 1 2 6 12 0.4 7 7 Max 17 13 2 15 15 15 3 5 20 2 13 13 Unit ns ns ns ns ns ns ns ns ns ns ns ns Test Conditions/Comments RL Diff = 54 , CL1 = CL2 = 100 pF, Test Circuit 3 RL Diff = 54 , CL1 = CL2 = 100 pF @ TA = 25C RL Diff = 54 , CL1 = CL2 = 100 pF, Test Circuit 3* RL Diff = 54 , CL1 = CL2 = 100 pF, Test Circuit 3 RL = 110 , CL = 50 pF, Test Circuit 4 RL = 110 , CL = 50 pF, Test Circuit 4 RL = 110 , CL = 50 pF, Test Circuit 4 RL = 110 , CL = 50 pF, Test Circuit 4 CL = 15 pF, Test Circuit 5 CL = 15 pF*, Test Circuit 5 CL = 15 pF, RL = 1 k, Test Circuit 6 CL = 15 pF, RL = 1 k, Test Circuit 6 DRIVER Propagation Delay Input to Output tPLH, tPHL Driver O/P to O/P tSKEW Driver Rise/Fall Time tR, tF Driver Enable to Output Valid tZH, tZL Driver Disable Timing tHZ, tLZ Matched Enable Switching |tAZH - tBZL|, |tBZH - tAZL| Matched Disable Switching |tAHZ - tBLZ|, |tBHZ - tALZ| RECEIVER Propagation Delay Input to Output tPLH, tPHL Skew |tPLH-tPHL| Receiver Enable tZH, tZL Receiver Disable tHZ, tLZ *Guaranteed by characterization. Specifications subject to change without notice. -2- REV. 0 ADM1486 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) . . . . . . . . . . . . . . . . . -9 V to +14 V Outputs Driver Outputs . . . . . . . . . . . . . . . . . . . . . . . -9 V to +14 V Receiver Output . . . . . . . . . . . . . . . . -0.5 V to VCC + 0.5 V Power Dissipation 8-Lead SOIC . . . . . . . . . . . . . . . . 450 mW JA, Thermal Impedance . . . . . . . . . . . . . . . . . . . 170C/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 *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 ADM1486AR Temperature Range -40C to +85C Package Description 8-Lead Narrow Body (SOIC) Package Option RN-8 CAUTION ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily accumulate on the human body and test equipment and can discharge without detection. Although the ADM1486 features proprietary ESD protection circuitry, permanent damage may occur on devices subjected to high energy electrostatic discharges. Therefore, proper ESD precautions are recommended to avoid performance degradation or loss of functionality. REV. 0 -3- ADM1486 PIN CONFIGURATION RO 1 RE 2 8 VCC B TOP VIEW DE 3 (Not to Scale) 6 A 7 ADM1486 DI 4 5 GND PIN FUNCTION DESCRIPTION Pin 1 2 3 4 5 6 7 8 Mnemonic RO RE DE DI GND A B VCC Function Receiver Output. When enabled, if A > B by 200 mV, RO = High. If A < B by 200 mV, RO = Low. Receiver Output Enable. A low level enables the receiver output, RO. A high level places it in a high impedance state. Driver Output Enable. A high level enables the driver differential outputs, A and B. A low level places it in a high impedance state. Driver Input. When the driver is enabled, a logic Low on DI forces A low and B high while a logic High on DI forces A high and B low. Ground Connection, 0 V Noninverting Receiver Input A/Driver Output A Inverting Receiver Input B/Driver Output B Power Supply, 5 V 5% Table I. Transmitting Table II. Receiving Inputs DE 1 1 0 DI 1 0 X B 0 1 Z Outputs A 1 0 Z RE 0 0 0 1 Inputs A-B +0.2 V -0.2 V Inputs Open X Output RO 1 0 1 Z -4- REV. 0 ADM1486 Test Circuits A R VOD R B DE IN 0V OR 3V VCC A RL S1 DE B CL VOUT S2 VOC Test Circuit 1. Driver Voltage Measurement Test Circuit 4. Driver Enable/Disable 375 A A B RE CL VOUT VOD3 B 60 375 VTST Test Circuit 2. Driver Voltage Measurement Test Circuit 5. Receiver Propagation Delay +1.5V A RLDIFF B VCC S1 RL S2 RE CL VOUT CL1 -1.5V CL2 RE IN Test Circuit 3. Driver Propagation Delay Test Circuit 6. Receiver Enable/Disable Switching Characteristics 3V 1.5V 0V B 1/2VO VO A 1.5V tPLH tPHL A, B 0V 0V tSKEW = tPLH-t PHL VO 0V -VO 10% POINT 10% POINT 90% POINT 90% POINT tPLH tPHL VOH RO 1.5V tSKEW = tPLH-tPHL 1.5V VOL tR tF Figure 1. Driver Propagation Delay, Rise/Fall Timing Figure 3. Receiver Propagation Delay 3V DE 1.5V 1.5V 0V RE 1.5V 1.5V 3V 0V tZL tLZ tZL tLZ A, B 2.3V VOL + 0.5V VOL R 1.5V O/P LOW VOL + 0.5V VOL tZH A, B 2.3V tHZ VOH VOH - 0.5V R tZH O/P HIGH tHZ VOH VOH - 0.5V 0V 0V 1.5V Figure 2. Driver Enable/Disable Timing Figure 4. Receiver Enable/Disable Timing REV. 0 -5- ADM1486-Typical Performance Characteristics 35 30 0.50 0.45 0.40 OUTPUT CURRENT - mA OUTPUT VOLTAGE - V 25 20 15 10 0.35 0.30 0.25 0.20 5 0 0 0.25 0.50 0.75 1.00 1.25 1.50 1.75 2.00 OUTPUT VOLTAGE - V 0.15 -50 -25 0 25 50 75 100 125 TEMPERATURE - C TPC 1. Output Current vs. Receiver Output Low Voltage TPC 4. Receiver Output Low Voltage vs. Temperature I = 8 mA 0 80 70 -5 60 OUTPUT CURRENT - mA OUTPUT CURRENT - mA -10 50 40 30 20 10 -15 -20 -25 0 -30 3.50 -10 3.75 4.00 4.25 4.50 4.75 5.00 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 OUTPUT VOLTAGE - V OUTPUT VOLTAGE - V TPC 2. Output Current vs. Receiver Output High Voltage TPC 5. Output Current vs. Driver Differential Output Voltage 4.75 3.00 2.95 4.70 2.90 OUTPUT VOLTAGE - V OUTPUT VOLTAGE - V 4.65 2.85 2.80 2.75 2.70 4.60 4.55 2.65 4.50 -50 2.60 -50 -25 0 25 50 75 100 125 -25 0 25 50 75 100 125 TEMPERATURE - C TEMPERATURE - C TPC 3. Receiver Output High Voltage vs. Temperature I = 8 mA TPC 6. Driver Differential Output Voltage vs. Temperature, RLDiff = 53.6 -6- REV. 0 ADM1486 80 70 1.4 1.3 1.2 1.1 OUTPUT CURRENT - mA 60 50 TIME - ns 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 40 30 20 10 0 1.0 0.9 0.8 0.7 0.6 -50 -25 0 25 50 75 100 125 OUTPUT VOLTAGE - V TEMPERATURE - C TPC 7. Output Current vs. Driver Output Low Voltage TPC 10. Receiver Skew vs. Temperature 0 -10 5.0 4.5 4.0 OUTPUT CURRENT - mA -20 3.5 -30 TPHLA - TPHLB TIME - ns 3.0 2.5 2.0 1.5 TPLHA - TPLHB -40 -50 -60 1.0 -70 -80 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 OUTPUT VOLTAGE - V CROSSPOINT A, B 0.5 0 -75 -50 -25 0 25 50 75 100 125 150 TEMPERATURE - C TPC 8. Output Current vs. Driver Output High Voltage TPC 11. Driver Skew vs. Temperature 1.30 1.25 1.20 1.0 0.9 0.8 DRIVER ENABLED OUTPUT CURRENT - mA 1.15 1.10 0.7 0.6 PWD 1.05 1.00 0.95 0.90 DRIVER DISABLED 0.85 0.80 -50 -25 0 25 50 75 100 125 0.5 0.4 0.3 0.2 0.1 0 -75 -50 -25 0 25 50 75 100 125 150 TPLH - TPHL TEMPERATURE - C TEMPERATURE - C TPC 9. Supply Current vs. Temperature TPC 12. Tx Pulsewidth Distortion REV. 0 -7- ADM1486 A 3 DI A B B 1, 2 1, 2 4 RO TPC 13. Unloaded Driver Differential Outputs TPC 16. Driver/Receiver Propagation Delays High to Low (RLDiff = 54 , CL1 = CL2 = 100 pF) A A B B 1, 2 1, 2 TPC 14. Loaded Driver Differential Outputs (RLDiff = 54 , CL1 = CL2 = 100 pF) TPC 17. Unloaded Driver Outputs at 15 Mbps DI 3 A A B 1, 2 RO 4 1, 2 B TPC 15. Driver/Receiver Propagation Delays Low to High (RLDiff = 54 , CL1 = CL2 = 100 pF) TPC 18. Unloaded Driver Outputs at 30 Mbps -8- REV. 0 ADM1486 B A B A 1, 2 1, 2 TPC 19. Loaded Driver Outputs at 15 Mbps (RLDiff = 54 , CL1 = CL2 = 100 pF) TPC 20. Loaded Driver Outputs at 30 Mbps (RLDiff = 54 , CL1 = CL2 = 100 pF) REV. 0 -9- ADM1486 APPLICATIONS INFORMATION Differential Data Transmission 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 that appear as common-mode voltages on the line. There are two main standards approved by the Electronics Industries Association (EIA) that 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 4,000 ft. A single driver can drive a transmission line with up to 10 receivers. In order to cater to true multipoint communications, the RS-485 standard was defined. This standard meets or exceeds all the requirements of RS-422, but also allows up to 32 drivers and 32 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 that the drivers may be disabled, allowing more than one (32 in fact) 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. Cable and Data Rate An RS-485 transmission line can have as many as 32 transceivers on the bus. 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. Thermal Shutdown The ADM1486 contains thermal shutdown circuitry that protects the part from excessive power dissipation during fault conditions. Shorting the driver outputs to a low impedance source can result in high driver currents. The thermal sensing circuitry detects the increase in die temperature and disables the driver outputs. The thermal sensing circuitry is designed to disable the driver outputs when a die temperature of 150C is reached. As the device cools, the drivers are re-enabled at 140C. Propagation Delay The ADM1486 features very low propagation delay, ensuring maximum baud rate operation. The driver is well balanced, ensuring distortion free transmission. Another important specification is a measure of the skew between the complementary outputs. Excessive skew impairs the noise immunity of the system and increases the amount of electromagnetic interference (EMI). Receiver Open-Circuit Fail-Safe 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 ADM1486 is designed for bidirectional data communications on multipoint transmission lines. A typical application showing a multipoint transmission network is illustrated in Figure 5. The receiver input includes a fail-safe feature that guarantees a logic high on the receiver when the inputs are open circuit or floating. RT RT D D R R R D D R Figure 5. Typical RS-485 Network -10- REV. 0 ADM1486 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 No. of Drivers/Receivers Per Line RS-422 Differential 4000 ft. 2 V 100 4 k min 200 mV -7 V to +7 V 1/10 RS-485 Differential 4000 ft. 1.5 V 54 12 k min 200 mV -7 V to +12 V 32/32 PROFIBUS Differential 2.1 V 54 20 k min 200 mV -7 V to +12 V 50/50 REV. 0 -11- ADM1486 OUTLINE DIMENSIONS 8-Lead Standard Small Outline Package [SOIC] Narrow Body (RN-8) Dimensions shown in millimeters and (inches) 5.00 (0.1968) 4.80 (0.1890) 8 5 4 4.00 (0.1574) 3.80 (0.1497) 1 6.20 (0.2440) 5.80 (0.2284) 1.27 (0.0500) BSC 0.25 (0.0098) 0.10 (0.0040) COPLANARITY SEATING 0.10 PLANE 1.75 (0.0688) 1.35 (0.0532) 8 0.25 (0.0098) 0 0.19 (0.0075) 0.50 (0.0196) 0.25 (0.0099) 45 0.51 (0.0201) 0.33 (0.0130) 1.27 (0.0500) 0.41 (0.0160) COMPLIANT TO JEDEC STANDARDS MS-012AA CONTROLLING DIMENSIONS ARE IN MILLIMETERS; INCH DIMENSIONS (IN PARENTHESES) ARE ROUNDED-OFF MILLIMETER EQUIVALENTS FOR REFERENCE ONLY AND ARE NOT APPROPRIATE FOR USE IN DESIGN -12- REV. 0 PRINTED IN U.S.A. C02603-0-11/02(0) |
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