DS485TM

DS485 NSC | Alldatasheet

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Technical content

Features

n Meets TIA/EIA RS-485 multipoint standard n Guaranteed full load output voltage (VOD3 ) n Low quiescent current: 200 µA typ n −7V to +12V common-mode input voltage range n TRI-STATE outputs on driver and receiver n AC performance: — Driver transition time: 25 ns typ — Driver propagation delay: 40 ns typ — Driver skew: 1 ns typ — Receiver propagation delay: 200 ns typ — Receiver skew: 20 ns typ n Half-duplex flow through pinout n Operates from a single 5V supply n Allows up to 32 transceivers on the bus n Current-limiting and thermal shutdown for driver overload protection n Industrial temperature range operation n Pin and functional compatible with MAX485 and LTC485 Connection and Logic Diagram Order Number Temp. Range Package/ ### DS485N 0˚C to +70˚C DIP/N08E DS485M 0˚C to +70˚C SOP/M08A DS485TN −40˚C to +85˚C DIP/N08E DS485TM −40˚C to +85˚C SOP/M08A Truth Table DRIVER SECTION RE * DE DI A B XHHHL XHL LH XLXZZ RECEIVER SECTION RE * DE A-B RO LL ≥+0.2V H LL ≤−0.2V L HX X Z L L OPEN * H *Note: Non Terminated, Open Input only X = indeterminate Z = TRI-STATE TRI-STATE® is a registered trademark of National Semiconductor Corporation. DIP and SOIC DS012880-1 July 1998 DS485 Low Power RS-485/RS-422 Multipoint Transceiver © 1999 National Semiconductor Corporation DS012880 www.national.com

Absolute Maximum Ratings(Note 1) If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications. Supply Voltage (V CC ) +12V Enable Input Voltage (RE*, DE) −0.5V to (V CC + 0.5V) Driver Input Voltage (DI) −0.5V to (V CC + 0.5V) Driver Output Voltage (A, B) −14V to +14V Receiver Input Voltage (A, B) −14V to +14V Receiver Output Voltage (RO) −0.5V to (V CC + 0.5V) Maximum Package Power Dissipation@ +25˚C M Package 1.19W N Package 0.74W Derate M Package 9.5 mW/˚C above +25˚C Derate N Package 6.0 mW/˚C above +25˚C Maximum Package Power Dissipation @ +70˚C M Package 0.76W N Package 0.47W Storage Temperature Range −65˚C to +150˚C Lead Temperature Range (Soldering, 4 sec.) +260˚C ESD (HBM) ≥2k V Recommended Operating Conditions Min Typ Max Units Supply Voltage (VCC ) +4.75 +5.0 +5.25 V Operating Free Air Temperature (T DS485 0 +25 +70 ˚C DS485T −40 +25 +85 ˚C Bus Common Mode Voltage −7 +12 V

Electrical Characteristics

Over Supply Voltage and Operating Temperature Ranges, unless otherwise specified (Notes 2, 3) Symbol Parameter Conditions Pin Min Typ Max Units VOD1 Differential Driver Output Voltage (No Load) A, B 5 V VOD2 Differential Driver Output Voltage R L = 50Ω , (RS422),Figure 1 2 2.8 V with Load R L = 27Ω , (RS485),Figure 1 1.5 2.3 5 V ΔVOD Change in Magnitude of Output R L = 27Ω or 50Ω (Note 4) 0.2 |V| Differential Voltage VOD3 Differential Driver Output Voltage — R1 = 54Ω ,R 2= 375Ω 1.5 2.0 5 V Full Load with Max VCM VTEST = −7V to +12V,Figure 5 VOC Driver Common-Mode Output Voltage R L = 27Ω or 50Ω ,Figure 1 3V ΔVOC Change in Magnitude of Common-Mode R L = 27Ω or 50Ω ,Figure 1(Note 4) 0.2 |V| Output Voltage VIH Input High Voltage DI, DE, RE * 2.0 V VIL Input Low Voltage 0.8 V IIN1 Input Current V IN = 0V or VCC ±2µ A IIN2 Input Current (Note 5) V IN = +12V A, B 1.0 mA DE = 0V, VCC = 0V or 5.25V V IN = −7V −0.8 mA VTH Receiver Differential Threshold Voltage −7V≤ VCM ≤ +12V −0.2 0.2 V ΔVTH Receiver Input Hysteresis V CM = 0V 70 mV VOH Receiver Output High Voltage I O = −4 mA, VID = 0.2V RO 3.5 V VOL Receiver Output Low Voltage I O = 4 mA, VID = −0.2V 0.4 V IOZR TRI-STATE Output Current at Receiver 0.4V≤ VO ≤ 2.4V ±1µ A R IN Receiver Input Resistance −7V ≤ VIN ≤ +12V A, B 12 k Ω ICC No-Load Supply Current (Note 6) DE = VCC ,R E* = 0V or VCC VCC 200 900 µA DE = 0V, RE* = 0V or VCC 200 500 µA IOSD1 Driver Short Circuit Current, VO = HIGH −7V ≤ VO ≤ +12V A, B 35 250 mA IOSD2 Driver Short Circuit Current, VO = LOW −7V ≤ VO ≤ +12V 35 250 mA IOSR Receiver Short Circuit Current 0V ≤ VO ≤ VCC RO 7 85 mA www.national.com 2

Over Supply Voltage and Operating Temperature Ranges, unless otherwise specified (Notes 3, 7, 8) Symbol Parameter Conditions Min Typ Max Units tPLHD Driver Differential Propagation Delay — Low to High RL = 54Ω ,C L = 100 pF 10 40 65 ns tPHLD Driver Differential Propagation Delay — High to Low 10 39 65 ns tSKEW Differential Skew |tPHLD −tPLHD | 1 10 ns tr Driver Rise Time 32 5 4 0 n s tf Driver Fall Time 32 5 4 0 n s tZH Driver Enable to Output High C L = 100 pF 170 ns tZL Driver Enable to Output Low C L = 100 pF 170 ns tLZ Driver Disable from Output Low C L = 15 pF 170 ns tHZ Driver Disable from Output High C L = 15 pF 170 ns tPLHD Receiver Differential Propagation Delay — Low to High CL = 15 pF (RO) 70 190 320 ns tPHLD Receiver Differential Propagation Delay — High to Low 70 210 320 ns tSKEW Differential Skew |tPHLD −tPLHD |2 0 5 0 n s tZH Receiver Enable to Output High C L = 15 pF 110 ns tZL Receiver Enable to Output Low 110 ns tLZ Receiver Disable from Output Low 110 ns tHZ Receiver Disable from Output High 110 ns fmax Maximum Data Rate (Note 9) 2.5 Mbps Note 1:“Absolute Maximum Ratings” are those values beyond which the safety of the device cannot be guaranteed. They are not meant to imply that the devices 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 referenced to ground except VOD1/2/3 and VID. Note 3:All typicals are given for: VCC = +5.0V, TA = +25˚C. Note 4:Δ|VOD | andΔ|VOC | are changes in magnitude of VOD and VOC respectively, that occur when the input changes state. Note 5:IIN2 includes the receiver input current and driver TRI-STATE leakage current. Note 6:Supply current specification is valid for loaded transmitters when DE= 0V or enabled (DE= H) with no load. Note 7: f= 1 MHz, tr and tf≤ 6 ns, ZO = 50Ω . Note 8:C L includes jig and probe capacitance. Note 9:fmax is the guaranteed data rate for 50 ft of twisted pair cable. fmax may be conservatively determined from the ratio of driver transition time (tr) to the data www.national.com3

Parameter Measurement Information(Continued) Pin Descriptions Pin # I/O Name Function 1 O RO Receiver Output: If A > B by 200 mV, RO will be high; If A< B by 200 mV, RO will be low. RO will be high also if the inputs (A and B) are open (non-terminated). 2I R E * Receiver Output Enable: RO is enabled when RE* is low; RO is in TRI-STATE when RE* is high.

3 I 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 I 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 I/O A Non-inverting Driver Output and Receiver Input pin. Driver output levels conform to RS-485 signaling levels. 7 I/O B Inverting Driver Output and Receiver Input pin. Driver output levels conform to RS-485 signaling levels. 8N A V CC Power Supply: 4.75V≤ VCC ≤ 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 www.national.com 6

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 fig- 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.com7

Physical Dimensionsinches (millimeters) unless otherwise noted Order Number DS485M or DS485TM Order Number DS485N or DS485TN www.national.com9

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- 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 to the user. 2. A critical component is any component of a life support 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. National Semiconductor Corporation Americas Tel: 1-800-272-9959 Fax: 1-800-737-7018 Email: support@nsc.com www.national.com National Semiconductor Europe Fax: +49 (0) 1 80-530 85 86 Email: europe.support@nsc.com Deutsch Tel: +49 (0) 1 80-530 85 85 English Tel: +49 (0) 1 80-532 78 32 Français Tel: +49 (0) 1 80-532 93 58 Italiano Tel: +49 (0) 1 80-534 16 80 National Semiconductor Asia Pacific Customer Response Group Tel: 65-2544466 Fax: 65-2504466 Email: sea.support@nsc.com National Semiconductor Japan Ltd. Tel: 81-3-5639-7560 Fax: 81-3-5639-7507 DS485 Low Power RS-485/RS-422 Multipoint Transceiver 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.