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national semiconductor DS485 Low Power RS-485/RS-422 Multipoint Transceiver handbook

1. www national com Applications Information The DS485 is a low power transceiver designed for use in RS 485 multipoint applications The DS485 can transmit data up to 2 5 Mbps based on a ratio of driver transition time to the unit interval bit time of 10 This maximum data rate may be further limited by the interconnecting media The DS485 provides a standard unit load to the RS 485 bus across the common mode range of 7V to 12V This allows up to 32 transceivers standard unit load to be connected to the bus More transceivers may be connected to the bus if they support a reduced unit load see DS36C278 The DS485 also guarantees the driver s output differential volt age into a worst case load that models standard termination loads and 32 unit loads referenced to the maximum common mode voltage extremes With a minimum of 1 5V swing into this load a 1 3V differential noise margin is supported along with the standard common mode rejection range of the re ceivers Due to the multipoint nature of the bus contention between drivers may occur This will not cause damage to the drivers since they feature short circuit protection and also thermal shutdown protection Thermal shutdown senses die tem perature and puts the driver outputs into TRI STATE if a fault condition occurs that causes excessive power dissipation which can elevate the junction temperature to 150 C A typical multipoint application is shown in the following f
2. 83 5 080 62 8 eT 1 a0 0 05 3 302 0 127 0 125 0 140 95 5 BEEN 0 065 3 175 3 556 lal FTO Sm 1j s 0 009 0 015 TETTE e 4 0 508 AL im EL a 3 175 0 229 0 381 SA TYP MIN 0 040 NOM l 0 018 0 003 0 325 Nas P 0 457 0 076 i255 5145 E 0 100 0 010 99 _ 9 381 2 540 0 254 0 045 0 015 1 143 0 381 d 0 060 mace g 1 524 1 270 NOBE REV F Order Number DS485N or DS485TN NS Package Number NO8E www national com DS485 Low Power RS 485 RS 422 Multipoint Transceiver LIFE SUPPORT POLICY NATIONAL S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DE VICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT OF NATIONAL SEMI CONDUCTOR CORPORATION As used herein 1 Life support devices or systems are devices or sys 2 A critical component is any component of a life support tems which a are intended for surgical implant into the body or b support or sustain life and whose fail ure to perform when properly used in accordance with instructions for use provided in the labeling can be reasonably expected to result in a significant injury device or system whose failure to perform can be rea sonably expected to cause the failure of the life support device or system or to affect its safety or effectiveness to the user National Semiconductor National Semiconductor National Semiconductor National
3. DO DAS 1 DJ DS485 General Description The DS485 is a low power transceiver for RS 485 and RS 422 communication The device contains one driver and one receiver The drivers slew rate allows for operation up to 2 5 Mbps see Applications Information section The transceiver draws 200 pA of supply current when un loaded or fully loaded with the driver disabled and operates from a single 5V supply The driver is short circuit current limited and is protected against excessive power dissipation by thermal shutdown circuitry that places the driver outputs into TRI STATE9 High Impedance state under fault conditions The driver guarantees a minimum of 1 5V differential output voltage with maximum loading across the common mode range Vons The receiver has a failsafe feature that guarantees a logic high output if the input is open circuit The DS485 is available in surface mount and DIP packages and is characterized for Industrial and Commercial tempera ture range operation July 1998 National Semiconductor Low Power RS 485 RS 422 Multipoint Transceiver Features Meets TIA EIA RS 485 multipoint standard Guaranteed full load output voltage V ops Low quiescent current 200 pA typ 7V to 12V common mode input voltage range TRI STATE outputs on driver and receiver AC performance Driver transition time 25 ns typ Driver propagation delay 40 ns typ Driver skew 1 ns typ Receiver propagation delay 200 n
4. Note 4 0 2 IV Output Voltage Input High Voltage DI 2 0 V Input Low Voltage DE 0 8 V Input Current Vin OV or Voc RE 2 yA Input Current Note 5 Vin 12V A B 1 0 mA DE OV Vec OV or 5 25V Vin 7V 0 8 mA Receiver Differential Threshold Voltage 7N Vom 12V 0 2 0 2 V Receiver Input Hysteresis Vom OV 70 mV Receiver Output High Voltage lo 4 mA Vip 0 2V RO 3 5 V Receiver Output Low Voltage lo 4 mA Vip 0 2V 0 4 V TRI STATE Output Current at Receiver 0 4V lt Vo lt 2 4V t1 HA Receiver Input Resistance 7V Vin 12V A B 12 kQ No Load Supply Current Note 6 DE Vec RE OV or Vec Vec 200 900 pA DE OV RE 0V or Voc 200 500 pA losp1 Driver Short Circuit Current Vo HIGH 7V lt Vo 12V A B 35 250 mA losp2 Driver Short Circuit Current Vo LOW 7V Vo 12V 35 250 mA losr Receiver Short Circuit Current OV lt Vo Voc RO 7 85 mA www national com 2 Switching Characteristics Over Supply Voltage and Operating Temperature Ranges unless otherwise specified Notes 3 7 8 Symbol Parameter Conditions Min Typ Max Units PLHD Driver Differential Propagation Delay Low to High R 549 C 100 pF 10 40 65 ns PHLD Driver Differential Propagation Delay High to Low 10 SKEW Differential Skew tpui p tei upl 1 10 ns Driver Rise Time 3 25 40 ns t Driver Fall Time 3 25 40 ns ZH Driver Enable to Output Hi
5. Semiconductor Corporation Europe Asia Pacific Customer Japan Ltd Americas Fax 49 0 1 80 530 85 86 Response Group Tel 81 3 5639 7560 Tel 1 800 272 9959 Email europe support nsc com Tel 65 2544466 Fax 81 3 5639 7507 Fax 1 800 737 7018 Deutsch Tel 49 0 1 80 530 85 85 Fax 65 2504466 Email support nsc com English Tel 49 0 1 80 532 78 32 Email sea support nsc com Frangais Tel 49 0 1 80 532 93 58 www national com Italiano Tel 49 0 1 80 534 16 80 National does not assume any responsibility for use of any circuitry described no circuit patent licenses are implied and National reserves the right at any time without notice to change said circuitry and specifications
6. ation is valid for loaded transmitters when DE OV or enabled DE H with no load f 1 MHz t and t lt 6 ns Zo 500 C includes jig and probe capacitance are not meant to imply that the devices erenced to ground except Vop1 2 3 and fmax is the guaranteed data rate for 50 ft of twisted pair cable f max may be conservatively determined from the ratio of driver transition time tr to the data www national com Parameter Measurement Information DO GENERATOR Do Ze DS012880 4 FIGURE 2 DI OUT OV OR 3V 5000 GENERATOR 900 51 to DO for DI 3V S1 to DO for DI 0V DS012880 6 FIGURE 3 DI OV OR 3V O OUT GENERATOR S1 to DO for DI 0V S1 to DO for DI 3V DS012880 8 FIGURE 4 Vtest 7V to 12V DS012880 3 FIGURE 5 Vons CP CROSSING POINT Vo DO DO ov t DS012880 5 FIGURE 6 SY DE ov Way VOH VOFF GND OUT 2 3V DS012880 7 FIGURE 7 Vg 0 5V DS012880 9 FIGURE 8 www national com Parameter Measurement Information continued GENERATOR pso12880 10 FIGURE 9 VoL DS012880 11 FIGURE 10 1 5V O GENERATOR DS012880 12 FIGURE 11 3v RE ov 1 1 5V 52 Voc Vec OUT EE M Vou DS012880 13 FIGURE 12 3V RE ov S1 41 5V S2 GND Vou OUT GND DS012880 14 FIGURE 13 5 www national com Parameter Mea
7. gh C 100 pF 170 ns ZL Driver Enable to Output Low C 100 pF 170 ns Lz Driver Disable from Output Low C 15 pF 170 ns HZ Driver Disable from Output High C 15 pF 170 ns PLHD Receiver Differential Propagation Delay Low to High C 15 pF RO PHLD Receiver Differential Propagation Delay High to Low SKEW Differential Skew tpui p ter upl ZH Receiver Enable to Output High C 15 pF ZL Receiver Enable to Output Low Lz Receiver Disable from Output Low Hz Receiver Disable from Output High f Maximum Data Rate Note 9 max Note 1 Absolute Maximum Ratings are those values beyond which the safety of the device cannot be guaranteed They should be operated at these limits The table of Electrical Characteristics specifies conditions of device operation Note 2 Current into device pins is defined as positive Current out of device pins is defined as negative All voltages are re Vip Note 3 Note 4 Note 5 Note 6 Note 7 Note 8 Note 9 rate unit interval 1 fmax Using a 10 ratio yields fmax 0 1 40 ns 2 5 Mb s Higher data rates may be supported by allowing larger ratios All typicals are given for Vcc 5 0V Ta 25 C A Vop and A Voc are changes in magnitude of V op and Vocrespectively that occur when the input changes state ling includes the receiver input current and driver TRI STATE leakage current Supply current specific
8. ig ure Note that termination is typically required but is only lo cated at the two ends of the cable not on every node Com monly pull up and pull down resistors may be required at one end of the bus to provide a failsafe bias These resistors pro vide a bias to the line when all drivers are in TRI STATE See National Application Note 847 for a complete discussion of failsafe biasing of differention buses Multipoint RS 485 Application DS012880 16 www national com Physical Dimensions inches millimeters unless otherwise noted 0 189 0 197 4 800 5 004 8 7 6 5 0 228 0 244 5 791 6 198 0 010 max 0 254 www 1 2 3 4 E IDENT TYP 0 150 0 157 3 810 3 988 1 053 0 069 0 010 0 020 45 TE EET 0 254 0 508 d NAT i ate 0 004 0 010 ALL LEADS 0 102 0 254 Y Sesh be el tat SEATING 009 f F A PLE 0 102 ooog 0010 Cee ng eu ss 0 050 0 014 0 020 qyp RES NIS aa 1 270 t 0 356 0 508 TYP ALL LEADS ne ESM ae MOBA REV H Order Number DS485M or DS485TM NS Package Number M08A 0 373 0 400 9 474 10 16 0 090 0 092 4 rt 0 032 0 005 2 337 0 813 0 127 l 0 250 0 005 RAD PIN N ne S 6 35 0 127 PIN NO 1 wR OPTION 1 0 280 py 7 112 0 030 TYP gt OPTION 2 MA 0 039 0 300 0 320 0 762 IL 0 145 0 200 1 628 128 i 20 T B 0 391 3 6
9. s typ Receiver skew 20 ns typ Half duplex flow through pinout Operates from a single 5V supply Allows up to 32 transceivers on the bus Current limiting and thermal shutdown for driver overload protection m Industrial temperature range operation m Pin and functional compatible with MAX485 and LTC485 Connection and Logic Diagram DIP and SOIC DS012880 1 Order Number Temp Range Package DS485N 0 C to 70 C DIP NO8E DS485M 0 C to 70 C SOP M08A DS485TN 40 C to 85 C DIP NO8E DS485TM 40 C to 85 C SOP M08A TRI STATE is a registered trademark of National Semiconductor Corporation Truth Table DRIVER SECTION RE DE DI A B X H H H L X H L L H X L X Z Z RECEIVER SECTION RE DE A B RO L L 2 0 2V H L L lt 0 2V L H X X Z L L OPEN H Note Non Terminated Open Input only X indeterminate Z TRI STATE 1999 National Semiconductor Corporation DS012880 www national com HIN ecv SH S8r SH J9eMog MOT S8rSa iod Lu J M JSULI Absolute Maximum Ratings Note 1 N Package 0 47W If Military Aerospace specified devices are required Storage Temperature Range 65 C to 150 C please contact the National Semiconductor Sales Office Lead Temperature Range Distributors for availabili
10. surement Information continued Pin Descriptions Pin O Name Function 1 O RO Receiver Output If A gt B by 200 mV RO will be high If A lt B by 200 mV RO will be low RO will be high also if the inputs A and B are open non terminated 2 l RE Receiver Output Enable RO is enabled when RE is low RO is in TRI STATE when RE is high 3 l DE Driver Output Enable The driver outputs A and B are enabled when DE is high they are in TRI STATE when DE is low Pins A and B also function as the receiver input pins see below 4 l DI Driver Input A low on DI forces A low and B high while a high on DI forces A high and B low when the driver is enabled 5 NA GND Ground 6 VO A Non inverting Driver Output and Receiver Input pin Driver output levels conform to RS 485 signaling levels 7 VO B Inverting Driver Output and Receiver Input pin Driver output levels conform to RS 485 signaling levels 8 NA Voc Power Supply 4 75V Voc lt 5 25V Related National Low Power RS 485 Transceivers Part Number Temperature Number of Comments Range XCVRs on Bus DS36C278 0 C to 70 C 128 Ultra Low Power Transceiver DS36C278T 40 C to 85 C 64 Ultra Low Power Transceiver DS36C279 0 C to 70 C 128 Auto Sleep Mode DS36C279T 40 C to 85 C 64 Auto Sleep Mode DS36C280 0 C to 70 C 128 Adjustable Slew Rate Control DS36C280T 40 C to 85 C 64 Adjustable Slew Rate Control
11. ty and specifications Soldering 4 sec 4260 C Supply Voltage Voc 12V ESD HBM 22 kV Enable Input Voltage RE DE 0 5V to Vcc 0 5V n Driver Input Voltage DI 0 5V to Vcc 0 5V Recommended Operating Driver Output Voltage A B 14V to 14V Conditions Receiver Input Voltage A B 14V to 14V Min Typ Max Units Receiver Output Voltage RO 0 5V to Vcc 0 5V Supply Voltage Vec 4475 450 4525 V Maximum Package Power Dissipation 25 C Operating Free Air M Package 1 19W Temperature Ta N Package Eid DS485 0 425 470 C Derate M Package 9 5 mW C above 25 C DS485T 40 425 485 C Derate N Package 6 0 mW C above 25 C Bus Common Mode Voltage 7 412 V Maximum Package Power Dissipation 70 C M Package 0 76W Electrical Characteristics Over Supply Voltage and Operating Temperature Ranges unless otherwise specified Notes 2 3 Symbol Parameter Conditions Pin Min Typ Max Units Vopi Differential Driver Output Voltage No Load A B 5 V Vop2 Differential Driver Output Voltage R 50Q RS422 Figure 1 2 28 V with Load R 27Q RS485 Figure 1 15 2 3 5 V AVop Change in Magnitude of Output R 27Q or 50Q Note 4 0 2 IVI Differential Voltage Vons Differential Driver Output Voltage R1 549 R2 3750 1 5 2 0 5 V Full Load with Max Vem Vrest 7V to 12V Figure 5 Voc Driver Common Mode Output Voltage R 27Q or 50 Figure 1 3 V AVoc Change in Magnitude of Common Mode R 27Q or 500 Figure 1

national semiconductor DS485 Low Power RS-485/RS-422 Multipoint Transceiver handbook

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