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ANALOG DEVICES ADM1485 +5 V Low Power EIA RS-485 Transceiver handbook

1. 50 0500 1 27 BSC z B 0 0099 0 25 0 0688 1 75 0 0098 0 25 _ 0 0532 1 35 _ 0 0040 0 10 4 B ais seATING amp 0182 0 49 0 0098 0 25 0 0 0500 1 27 PLANE 0 0138 0 35 0 0075 0 19 00160 0 41 8 Lead Plastic DIP N 8 0 430 10 92 gt 0 348 8 84 0 280 7 11 0 240 6 10 PIN 17 0 325 8 25 0 300 7 62 0 060 1 52 0 210 0 015 0 38 0 195 4 95 Een 0 115 2 93 0 130 0 160 4 06 3 30 0 115 2 93 MIN wie 0 015 0 381 0 022 0 558 0 070 1 77 SEATING 0 008 0 204 0 014 0 356 0 045 1 15 PLANE 8 Lead Cerdip Q 8 0 005 0 13 0 055 l 4 MIN oe the 8 5 0 310 7 87 0 220 5 59 el 4 PIN 0 320 8 13 0 405 10 29 EEEN ee js 29 0 060 1 52 0 290 7 37 0 200 5 08 0 015 0 38 MAX af 150 0 200 5 08 Sig 0 125 3 18 aile JRR ENEN gt l 0 015 0 38 0 023 0 58 0 100 0 l 1 78 Bed 15 0 008 0 20 0 014 0 36 2 54 0 030 0 76 BSC REV A C1818 0 6 00 rev A 00063 PRINTED IN U S A
2. Driver Differential Outputs Figure 24 Driver Receiver Propaga tion Delays Low to High Figure 25 Driver Receiver Propaga tion Delays High to Low Figure 26 Typical RS 485 Network REV A ADM1485 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 which appear as common mode voltages on the line There are two main standards approved by the Electronics Industries Association EIA which specify the electrical charac teristics 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 transmis sion line with up to 10 receivers In order to cater for true multipoint communications the RS 485 standard was defined This standard meets or exceeds all the requirements of RS 422 but also allows for 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 the fact that the drivers may be disabled thereby allowing more than one 32 in fact to be connected to a single line Only one driver should be enabled at time but the RS 485 standard contains additional specifications t
3. WARNING maa ESD SENSITIVE DEVICE REV A ADM1485 Test Circuits Figure 1 Driver Voltage Measurement Test Circuit Figure 4 Driver Enable Disable Test Circuit 3750 Figure 2 Driver Voltage Measurement Test Circuit 2 Figure 5 Receiver Propagation Delay Test Circuit Cu O RLbIFF t 5 Cio Figure 3 Driver Propagation Delay Test Circuit Figure 6 Receiver Enable Disable Test Circuit Switching Characteristics 3V Vou 90 POINT 90 POINT VoL 10 POINT 3V DE R 1 5V A B O P LOW Vor 0 5V VoL VoL Dl Tzu e gt Tiz Tzu Taz O P HIGH Von Vou Von 0 5V Von 0 5V A B za OH R EV OH ov ov Figure 8 Driver Enable Disable Timing Figure 10 Receiver Enable Disable Timing A REV A Typical Performance Characteristics ADM1485 OUTPUT CURRENT mA 0 0 5 1 0 1 5 2 0 OUTPUT VOLTAGE Volts Figure 11 Receiver Output Low Voltage vs Output Current 0 4 o w OUTPUT VOLTAGE Volts iv 0 1 50 25 0 25 50 75 100 125 TEMPERATURE C Figure 14 Receiver Output Low Voltage vs Temperature 100 OUTPUT CURRENT mA 0 1 2 3 4 OUTPUT VOLTAGE Volts Figure 17 Driver Output Low Voltage vs Output Current REV A OUTPUT CURRENT mA 3 5 4 0 4 5 5 0 OUTPUT VOLTAGE Volts Fig
4. AAD M 1485 t ny Fy ANALOG DEVICES 5 V Low Power EIA RS 485 Transceiver ADM1485 FEATURES Meets EIA RS 485 Standard 30 Mb s Data Rate Single 5 V Supply 7 V to 12 V Bus Common Mode Range High Speed Low Power BiCMOS Thermal Shutdown Protection Short Circuit Protection Zero Skew Driver Driver Propagation Delay 10 ns Receiver Propagation Delay 25 ns High Z Outputs with Power Off Superior Upgrade for LTC1485 APPLICATIONS Low Power RS 485 Systems DTE DCE Interface Packet Switching Local Area Networks Data Concentration Data Multiplexers Integrated Services Digital Network ISDN GENERAL DESCRIPTION The ADM 1485 is a differential line transceiver suitable for high speed bidirectional data communication on multipoint bus transmission lines It is designed for balanced data transmission and complies with both EIA Standards RS 485 and RS 422 The part contains a differential line driver and a differential line receiver Both the driver and the receiver may be enabled inde pendently When disabled the outputs are tristated The ADM1485 operates from a single 5 V power supply 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 Up to 32 transceivers may be connected sim
5. Mbits s 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 DIL SOIC package 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 Analog Devices Inc 2000 AD M 1 485 SPEC FI CATI 0 NS Veg 5 V 5 All specifications Ty to Tyax unless otherwise noted Parameter Min Typ Max Unit Test Conditions Comments DRIVER Differential Output Voltage Vop 5 0 V R oo Figure 1 2 0 5 0 V Vee 5 V R 50 Q RS 422 Figure 1 1 5 5 0 V R 27 Q RS 485 Figure 1 Vop3 1 5 5 0 V Vest 7 V to 12 V Figure 2 A Vop for Complementary Output States 0 2 V R 27 Q or 50 Q Figure 1 Common Mode Output Voltage Voc 3 V R 27 Q or 50 Q Figure 1 A Vop for Complementary Output States 0 2 V R 27Q or 50Q Output Short Circuit Current Voyr High 35 250 mA TVS Vos 12 V Output Short Circuit Current Voy Low 35 250 mA 7TV lt Vos 12 V CMOS Input Logic Threshold Low Vin 0 8 V CMOS Input Logic Threshold High Ving 2 0 V Logic Input Current DE DI 1 0 uA RECEIVER Differential Input Threshold Voltage Vru 0 2 0 2 V 7 V lt Vcm lt 12 V Input Voltage Hysteresis AVru 70 mV Vem 0V Input Resistance 12 KQ 7 V lt Vcem lt 12 V Input Current A B 1 mA Vw 12V 0 8 mA Vin 7V Logic Enable Input Current RE 1 uA CMOS Output Vo
6. ensing circuitry is designed to disable the driver outputs when a die temperature of 150 C is reached As the device cools the drivers are re enabled at 140 C Propagation Delay The ADM1485 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 be tween the complementary outputs Excessive skew impairs the noise immunity of the system and increases the amount of elec tromagnetic interference EMI Receiver Open Circuit Fail Safe The receiver input includes a fail safe feature which 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 RS 422 RS 485 Transmission Type Differential Differential Maximum Cable Length 4000 ft 4000 ft Minimum Driver Output Voltage 2V 1 5V Driver Load Impedance 100 Q 54 Q Receiver Input Resistance 4 KQ min 12 kQ min Receiver Input Sensitivity 200 mV 200 mV Receiver Input Voltage Range 7 V to 7 V 7 V to 12 V No of Drivers Receivers Per Line 1 10 32 32 REV A ADM1485 OUTLINE DIMENSIONS Dimensions shown in inches and mm 0 1968 5 00 7 0 1890 an 8 Lead SOIC SO 8 8 5 0 1574 4 00 L 0 2440 6 20 0 1497 3 80 IT 0 2284 5 80 t z ZH H ak 0 0500 12 0 0196 0
7. ltage Low VoL 0 4 V Iour 4 0 mA CMOS Output Voltage High Voy 4 0 V Iour 4 0 mA Short Circuit Output Current 7 85 mA Vout GND or Vec Tristate Output Leakage Current 1 0 uA 0 4 V lt Vout lt 2 4 V POWER SUPPLY CURRENT Icc Outputs Enabled 1 35 2 2 mA Outputs Unloaded Digital Inputs GND or Vec Icc Outputs Disabled 0 7 1 mA Outputs Unloaded Digital Inputs GND or Vcc Specifications subject to change without notice TIMING SPECIFICATIONS Veg 5 V 5 All specifications Tu to Tmax unless otherwise noted Parameter Min Typ Max Unit Test Conditions Comments DRIVER Propagation Delay Input to Output Toru Tpur 2 10 15 ns R Diff 54 Q Cy Cr 100 pF Figure 3 Driver O P to O P Tsxsw 0 5 ns R Diff 54 Q Cy Cr 100 pF Figure 3 Driver Rise Fall Time Tr Tr 2 10 ns R Diff 54 Q Cy Ci 100 pF Figure 3 Driver Enable to Output Valid 10 25 ns Driver Disable Timing 10 25 ns RECEIVER Propagation Delay Input to Output Tpry TpuL 18 25 40 ns Cr 15 pF Figure 5 Skew Tpiy Tput 0 5 ns Receiver Enable Ten 15 25 ns Figure 6 Receiver Disable Tgn2 15 25 ns Figure 6 Specifications subject to change without notice REV A ADM1485 PIN FUNCTION DESCRIPTION ABSOLUTE MAXIMUM RATINGS Ta 25 C unless otherwise noted Pin Mnemonic Function Vee Annie We Bia Bet ee ENS Me 7 V Inputs 1 RO Receiver Ou
8. o guarantee device safety in the event of line contention Cable and Data Rate 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 gener ated by the current flowing through each wire thereby reducing the effective inductance of the pair The ADM1485 is designed for bidirectional data communica tions on multipoint transmission lines A typical application showing a multipoint transmission network is illustrated in Figure 26 An RS 485 transmission line can have as many as 32 transceivers on the bus Only one driver can transmit at a par ticular 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 im pedance 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 ADM1485 contains thermal shutdown circuitry which 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 s
9. ting Receiver Input B Driver Output B Vapor Phase 60 sec a 215 C 8 Vee Power Supply 5 V 5 Infrared 15SEC auh srad ala Metel Anda oes ye 220 C Stresses above those listed under Absolute Maximum Ratings may cause perma nent damage to the device This is a stress rating only Ae RE of the PIN CONFIGURATION device at these or any other conditions above those listed in the operational sections ofthis specification is not implied Exposure to absolute maximum ratings for extended periods of time may affect device reliability Ro o 8 Voc r RE 2 ADM1485 7 B Table I Transmitting pe zl LA on INPUTS OUTPUTS pi a 5 enD RE DE DI B A 7 l l 9 l ORDERING GUIDE X 1 0 1 0 X 0 X Z Z Temperature Package Model Range Option Table II Receiving ADM1485JN 0 C to 70 C N 8 ADM1485JR 0 C to 70 C SO 8 a INPUTS OUTPUT __ADM1485AN 40 C to 85 C N 8 RE DE AB RO ADM1485AR 40 C to 85 C SO 8 0 0 gt 0 2 V 1 ADM1485AQ 40 C to 85 C Q 8 0 0 lt 0 2 V 0 0 0 Inputs Open 1 1 0 X Z 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 ADM1485 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
10. tput When enabled if A gt B Driver Input DI 0 3 V to Vcc 0 3 V by 200 mV then RO High If A lt B by Control Inputs DE RE 0 3 V to Vcc 0 3 V 200 mV then RO Low Receiver Inputs A B 0 14Vtot l4V 2 RE Receiver Output Enable A low level enables Outputs the receiver output RO A high level places Driver Outputs 0 0 00 0000008 14 V to 14 V it in a high impedance state Receiver Output 0 5 V to Vcc 0 5 V 3 DE Driver Output Enable A high level enables Power Dissipation 8 Lead DIP 500 mW the driver differential outputs A and B A Oja Thermal Impedance basics Abebe cba teense 130 C W low level places it in a high impedance state Power Dissipation 8 Lead SOIC 450 mW 4 DI Driver Input When the driver is enabled a Oja Thermal Impedance 170 C W idee DI f Al d B high RR l gic Low on orces A low an ig Power Dissipation 8 Lead Cerdip 500 mW while a logic High on DI forces A high and Oja Thermal Impedance 125 C W B low Operating Temperature Range 7 Commercial J Version 0 C to 70 C 5 GND Ground Connection 0 V Industrial A Version 40 C to 85 C 6 A Noninverting Receiver Input A Driver Storage Temperature Range 65 C to 150 C Output A Lead Temperature Soldering 10 sec 300 C 7 B Inver
11. ultaneously on a bus but only one driver should be enabled at any time It is important therefore that the remaining disabled drivers do not load the bus To ensure this the ADM1485 driver features high output impedance when disabled and also when powered down REV A 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 FUNCTIONAL BLOCK DIAGRAM 8 Lead ADM1485 1 8 Vee O O 2 B This minimizes the loading effect when the transceiver is not being utilized 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 which results in a logic high output state if the inputs are unconnected floating The ADM1485 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 ADM1485 features extremely fast switching speeds Mini mal driver propagation delays permit transmission at data rates up to 30
12. ure 12 Receiver Output High Voltage vs Output Current OUTPUT CURRENT mA A 0 1 2 3 4 OUTPUT VOLTAGE Volts Figure 15 Driver Differential Out put Voltage vs Output Current OUTPUT CURRENT mA d 0 4 2 3 4 5 OUTPUT VOLTAGE Volts Figure 18 Driver Output High Voltage vs Output Current 5 0 4 9 4 8 4 7 OUTPUT VOLTAGE Volts 4 6 4 5 50 25 0 25 50 75 100 125 TEMPERATURE C Figure 13 Receiver Output High Voltage vs Temperature 2 4 N w N 2 DIFFERENTIAL VOLTAGE Volts N N 2 0 50 25 0 25 50 75 100 125 TEMPERATURE C Figure 16 Driver Differential Output Voltage vs Temperature R 54Q DRIVER ENABLED DRIVER DISABLED SUPPLY CURRENT mA 50 25 0 25 50 75 100 125 TEMPERATURE C Figure 19 Supply Current vs Temperature ADM1485 Typical Performance Characteristics TIME ns 5 4 3 2 1 0 50 25 0 25 50 TEMPERATURE C Figure 20 Receiver tp tpy VS Temperature 75 100 125 1 0 0 4 50 25 0 25 50 75 100 125 TEMPERATURE C Figure 21 Driver Skew vs Temperature TANT T I ne HNE Figure 22 Unloaded Driver Differential Outputs Figure 23 Loaded

ANALOG DEVICES ADM1485 +5 V Low Power EIA RS-485 Transceiver handbook

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