LMS485

LMS485 NSC | Alldatasheet

Document overview

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Technical content

Features

n Meet ANSI standard RS-485-A and RS-422-B n Data rate 2.5 Mbps n Single supply voltage operation, 5V n Thermal shutdown protection n Short circuit protection n Low power BiCMOS n Allows up to 32 transceivers on the bus n Open circuit fail-safe for receiver n Extended operating temperature range −40˚C to 85˚C n Drop-in replacement to MAX485 n Available in 8-pin SOIC and 8-Pin DIP package

Applications

n Low power RS-485 systems n Network hubs, bridges, and routers n Point of sales equipment (ATM, barcode scanners,…) n Local area networks (LAN) n Integrated service digital network (ISDN) n Industrial programmable logic controllers n High speed parallel and serial applications n Multipoint applications with noisy environment Typical Application 20062601 A Typical multipoint application is shown in the above figure. Terminating resistors, RT, are typically required but only located at the two ends of th e cable. Pull up and pull down resistors maybe required at the end of the bus to provide failsafe biasing. The biasing resistors provide a bias to the cable when al l drivers are in TRI-STATE, See National Application Note, AN-847 for further information. April 2003 LMS485 5V Low Power RS-485 / RS-422 Differential Bus Transceiver © 2003 National Semiconductor Corporation DS200626 www.national.com

LL ≥ +0.2V H LL ≤ −0.2V L HX X Z L L OPEN * H Note: * = Non Terminated, Open Input only X = Irrelevant Z = TRI-STATE H = High level L = Low level 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 200mV, 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 N/A 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

8 N/A V

CC Power Supply: 4.75V ≤ VCC ≤ 5.25V LMS485 www.national.com 2

Ordering Information

Package Part Number Package Marking Transport Media NSC Drawing 8-Pin SOIC LMS485CM LMS485CM 95 Units/Rail M08ALMS485CMX 2.5k Units Tape and Reel LMS485IM LMS485IM 95 Units/Rail LMS485IMX 2.5k Units Tape and Reel 8-Pin DIP LMS485CNA LMS485CNA 40 Units/Rail N08ELMS485INA LMS485INA 40 Units/Rail LMS485 www.national.com3

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 (Note 2) 7V Input Voltage, VIN (DI, DE, or RE) −0.3V to V CC + 0.3V Voltage Range at Any Bus Terminal (AB) −7V to 12V Receiver Outputs −0.3V to V CC + 0.3V Package Thermal Impedance, θJA SOIC 125˚C/W DIP 88˚C/W Junction Temperature (Note 3) 150˚C Operating Free-Air Temperature Range, T A Commercial 0˚C to 70˚C Industrial −40˚C to 85˚C Storage Temperature Range −65˚C to 150˚C Soldering Information Infrared or Convection (20 sec.) 235˚C Lead Temperature (4 sec.) 260˚C ESD Rating (Note 4) 7kV Operating Ratings Min Nom Max Supply Voltage, VCC 4.75 5.0 5.25 V Voltage at any Bus Terminal (Separately or Common Mode) −7 12 V VIN or VIC High-Level Input Voltage, V IH (Note 5) Low-Level Input Voltage, V IL (Note 5) 0.8 V Differential Input Voltage, V ID (Note 6) ±12 V High-Level Output Driver, IOH −150 mA Receiver, IOH −42 mA Low-Level Output Driver, IOL 80 mA Receiver, IOL 26 mA

Electrical Characteristics

Over recommended ranges of supply voltage and operating free-air temperature (unless otherwise noted) Symbol Parameter Conditions Min Typ Max Units Driver Section OD1 | Differential Output Voltage R = ∞ (Figure 1) 5.25 V |V OD2 | Differential Output Voltage R = 50 Ω (Figure 1) ,RS-422 2.0 V R=2 7 Ω (Figure 1) ,RS-485 1.5 5.0 ∆VOD Change in Magnitude of Driver Differential Output Voltage for Complementary Output States R=2 7 Ω or 50Ω (Figure 1), (Note 7) 0.2 V V OC Common-Mode Output Voltage R=2 7 Ω or 50Ω (Figure 1) 3.0 V ∆VOC Change in Magnitude of Driver Common-Mode Output Voltage for Complementary Output States R=2 7 Ω or 50Ω (Figure 1), (Note 7) 0.2 V V IH CMOS Inout Logic Threshold High DE, DI, RE 2.0 V VIL CMOS Input Logic Threshold Low DE, DI, RE 0.8 V IIN1 Logic Input Current DE, DI, RE ±2µ A Receiver Section I IN2 Input Current (A, B) DE = 0V, V CC = 0V or 5.25V VIN = 12V 1.0 mA VIN = − 7V −0.8 VTH Differential Input Threshold Voltage ∆VTH Input Hysteresis Voltage (VTH+ −V TH−) VCM = 0 95 mV LMS485 www.national.com 4

Electrical Characteristics (Continued) Over recommended ranges of supply voltage and operating free-air temperature (unless otherwise noted) Symbol Parameter Conditions Min Typ Max Units VOH CMOS High-level Output Voltage IOH = −4mA, V ID = 200mV 3.5 V VOL CMOS Low-level I OL = 4mA, VID = −200mV 0.40 V IOZR Tristate Output Leakage Current 0.4V ≤ VO ≤ + 2.4V ±1µ A RIN Input Resistance − 7V ≤ VCM≤+12V 12 k Ω Power Supply Current I CC Supply Current DE = V CC, RE = GND or V CC 320 500 µA DE = 0V, RE = GND or V CC 315 400 IOSD1 Driver Short-circuit Output Current VO = high, −7V ≤ VCM ≤ + 12V (Note 8) 35 250 mA IOSD2 Driver Short-circuit Output Current VO = low, − 7V ≤VCM ≤ + 12V (Note 8) 35 250 mA IOSR Receiver Short-circuit Output Current 0V ≤VO ≤ VCC 79 5 m A Switching Characteristics Driver T PLH, TPHL Propagation Delay Input to Output R L =5 4Ω,C L = 100pF (Figure 3, Figure 7) 10 35 60 nS TSKEW Driver Output Skew R L =5 4Ω,C L = 100 pF (Figure 3, Figure 7) 51 0 n S TR, TF Driver Rise and Fall Time R L =5 4Ω,C L = 100 pF (Figure 3, Figure 7) 3 8 40 nS TZH, TZL Driver Enable to Ouput Valid Time C L = 100 pF, R L = 500Ω (Figure 4, Figure 8) 25 70 nS THZ, TLZ Driver Output Disable Time C L = 15 pF, R L = 500Ω (Figure 4, Figure 8) 30 70 nS Receiver TPLH, TPHL Propagation Delay Input to Output R L =5 4Ω,C L = 100 pF (Figure 5, Figure 7) 20 50 200 nS TSKEW Receiver Output Skew R L =5 4Ω,C L = 100 pF (Figure 5, Figure 7) 5n S TZH, TZL Receiver Enable Time C L = 15 pF, R L =1k Ω (Figure 6, Figure 10) 20 50 nS Receiver Disable Time 20 50 nS FMAX Maximum Data Rate 2.5 Mbps Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for which the device is intended to be functional, but specific performance is not guaranteed. For guaranteed specifications and the test conditions, see the Electrical Ch aracteristics Note 2: All voltage values, except differential I/O bus voltage, are with respect to network ground terminal. Note 3: The maximum power dissipation is a function of T J(MAX), θJA, and T A. The maximum allowable power dissipation at any ambient temperature is P D = (TJ(MAX) -T A)/θJA. All numbers apply for packages soldered directly into a PC board. Note 4: ESD rating based upon human body model, 100pF discharged through 1.5k Ω. Note 5: Voltage limits apply to DI, DE, RE pins. Note 6: Differential input/output bus voltage is measured at the non-inverting terminal A with respect to the inverting terminal B. Note 7: |∆VOD| and |∆VOC| are changes in magnitude of V OD and VOC, respectively when the input changes from high to low levels. Note 8: Peak current LMS485 www.national.com5

Typical Performance Characteristics Output Current vs. Receiver Output Low Voltage Output Current vs. Receiver Output High Voltage 20062613 20062614 Receiver Output High Voltage vs. Temperature Receiver Output Low-Voltage vs. Temperature 20062615 20062616 Driver Output Current vs. Differential Output Voltage Driver Differential Output Voltage vs. Temperature 20062617 20062618 LMS485 www.national.com 6

Typical Performance Characteristics (Continued) Output Current vs. Driver Output Low Voltage Output Current vs. Driver Output High Voltage 20062619 20062620 Supply Current vs. Temperature 20062621 LMS485 www.national.com7

Application Information

POWER LINE NOISE FILTERING A factor to consider in designing power and ground is noise filtering. A noise filtering circuit is designed to prevent noise generated by the integrated circuit (IC) as well as noise entering the IC from other devices. A common filtering method is to place by-pass capacitors (C bp) between the power and ground lines. Placing a by-pass capacitor (C bp) with the correct value at the proper location solves many power supply noise prob- lems. Choosing the correct capacitor value is based upon the desired noise filtering range. Since capacitors are not ideal, they may act more like inductors or resistors over a specific frequency range. Thus, many times two by-pass capacitors may be used to filter a wider bandwidth of noise. It is highly recommended to place a larger capacitor, such as 10µF, between the power supply pin and ground to filter out low frequencies and a 0.1µF to filter out high frequencies. By-pass capacitors must be mounted as close as possible to the IC to be effective. Long leads produce higher impedance at higher frequencies due to stray inductance. Thus, this will reduce the by-pass capacitor’s effectiveness. Surface mounted chip capacitors are the best solution because they have lower inductance. 20062622 FIGURE 11. Placement of by-pass Capacitors, Cbp

Physical Dimensions inches (millimeters) unless otherwise noted 8-Pin SOIC 8-Pin DIP LMS485 www.national.com 12

NATIONAL’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT AND GENERAL COUNSEL OF NATIONAL SEMICONDUCTOR CORPORATION. As used herein: 1. Life support devices or systems are devices or systems which, (a) are intended for surgical implant into the body, or (b) support or sustain life, and whose failure 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 reasonably expected to cause the failure of the life support device or system, or to affect its safety or effectiveness. National Semiconductor Americas Customer Support Center Email: new.feedback@nsc.com Tel: 1-800-272-9959 National Semiconductor Europe Customer Support Center Fax: +49 (0) 180-530 85 86 Email: europe.support@nsc.com Deutsch Tel: +49 (0) 69 9508 6208 English Tel: +44 (0) 870 24 0 2171 Français Tel: +33 (0) 1 41 91 8790 National Semiconductor Asia Pacific Customer Support Center Email: ap.support@nsc.com National Semiconductor Japan Customer Support Center Fax: 81-3-5639-7507 Email: jpn.feedback@nsc.com Tel: 81-3-5639-7560 www.national.com LMS485 5V Low Power RS-485 / RS-422 Differential Bus Transceiver National does not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and National reserves the righ t at any time without notice to change said circuitry and specifications.