LMS1485MX

LMS1485 5V Low Power RS-485 Differential Bus Transceiver July 2003 LMS1485 5V Low Power RS-485 Differential Bus Transceiver General Description The LMS1485 is a low power differential bus/line transceiver designed for high speed bidirectional data communication on multipoint bus transmission lines. It is designed for balanced transmission lines. It meets ANSI Standards TIA/EIA RS422-B, TIA/EIA RS485-A and ITU recommendation and V.11 and X.27. The LMS1485 combines a TRI-STATE™ differential line driver and differential input receiver, both of which operate from a single 5.0V power supply. The driver and receiver have an active high and active low, respectively, that can be externally connected to function as a direction control. The driver and receiver differential inputs are internally connected to form differential input/output (I/O) bus ports that are designed to offer minimum loading to bus whenever the driver is disabled or when VCC = 0V. These ports feature wide positive and negative common mode voltage ranges, making the device suitable for multipoint applications in noisy environments. The LMS1485 is build with National’s advanced BiCMOS process and is available in a 8-Pin SOIC package. It is a drop-in socket replacement to ADI’s ADM1485 and LTC’s LT1485. Features n n n n n n n n n n n n n n n Meet ANSI standard RS-485-A and RS-422-B Data rate 30Mbps Single supply voltage operation, 5V Wide input and output voltage range Thermal shutdown protection Short circuit protection Driver propagation delay 10ns Receiver propagation delay 25ns High impedance outputs with power off Open circuit fail-safe for receiver Extended operating temperature range −40˚C to 85˚C ESD rating 8kV HBM Drop-in replacement to ADM1485 and LT1485 Available in 8-pin SOIC Low supply current, ICC = 1mA Applications n n n n n n n n Low power RS-485 systems Network hubs, bridges, and routers Point of sales equipment (ATM, barcode scanners,…) Local area networks (LAN) Integrated service digital network (ISDN) Industrial programmable logic controllers High speed parallel and serial applications Multipoint applications with noisy environment Typical Application 20048801 A typical multipoint application is shown in the above figure. Terminating resistors, RT, are typically required but only located at the two ends of the 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 all drivers are in TRI-STATE, See National Application Note, AN-847 for further information. © 2003 National Semiconductor Corporation DS200488 www.national.com LMS1485 Connection Diagram 8-Pin SOIC 20048802 Top View Ordering Information Package Part Number LMS1485M 8-Pin SOIC LMS1485MX LMS1485IM LMS1485IMX Package Marking LMS1485M LMS1485IM Transport Media 95 Units/Rail 2.5k Units Tape and Reel 95 Units/Rail 2.5k Units Tape and Reel M08A NSC Drawing Pin Descriptions Pin # I/O 1 2 3 4 5 6 7 8 O I I I N/A I/O I/O N/A Name RO RE DE DI GND A B VCC Function 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) Receiver Output Enable: RO is enabled when RE is low; RO is in TRI-STATE when RE is high 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) 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 Ground Non-inverting Driver Output and Receiver Input pin. Driver Output levels conform to RS-485 signaling levels Inverting Driver Output and Receiver Input pin. Driver Output levels conform to RS-485 signaling levels Power Supply: 4.75V ≤ VCC ≤ 5.25V Truth Table DRIVER SECTION RE X X X RECEIVER SECTION RE L L H L Note: * = Non Terminated, Open Input only X = Irrelevant Z = TRI-STATE H = High level L = Low level DE H H L DE L L X L DI H L X A-B ≥ +0.2V ≤ −0.2V X OPEN * A H L Z B L H Z RO H L Z H www.national.com 2 LMS1485 Absolute Maximum Ratings (Note 1) ESD Rating (Note 4) (Note 9) Soldering Information Infrared or Convection (20 sec.) 2kV 235˚C If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications. Supply Voltage, VCC (Note 2) Input Voltage, VIN (DI, DE, or RE) Voltage Range at Any Bus Terminal (AB) Receiver Outputs Package Thermal Impedance, θJA SOIC (Note 3) Junction Temperature (Note 3) Operating Free-Air Temperature Range, TA Commercial Industrial Storage Temperature Range ESD Rating (Note 4) (Note 8) 0˚C to 70˚C −40˚C to 85˚C −65˚C to 150˚C 8kV 125˚C/W 150˚C 7V −0.3V to VCC+ 0.3V −7V to 12V −0.3V to VCC + 0.3V Operating Ratings Min Nom Max Supply Voltage, VCC Voltage at any Bus Terminal (Separately or Common Mode) VIN or VIC High-Level Input Voltage, VIH (Note 5) Low-Level Input Voltage, VIL (Note 5) Differential Input Voltage, VID (Note 6) 2 0.8 V V V 4.75 −7 5.0 5.25 12 V V ± 12 Electrical Characteristics Over recommended ranges of supply voltage and operating free-air temperature (unless otherwise noted) Symbol Driver Section VOD VOD1 VOD2 VOD3 ∆VOD VOC ∆VOC Differential Output Voltage Differential Output Voltage Differential Output Voltage Differential Output Voltage Change in Magnitude of Differential Output Voltage Common-Mode Output Voltage Change in Magnitude of Common-Mode Output Voltage Short-Circuit Output Current CMOS Input Logic Threshold Low CMOS Input Logic Threshold High Logic Input Current Differential Input Threshold Voltage Input Hysteresis Voltage (VTH+ − VTH−) Input Resistance Input Current (A, B) Logic Enable Input Current CMOS Low-Level Output Voltage R = ∞ (Figure 1) R = 50Ω (Figure 1), RS-422 R = 27Ω (Figure 1), RS-485 VTEST = −7V to + 12V (Figure 2) R = 27Ω or 50Ω (Figure 1 ), (Note 7) R = 27Ω or 50Ω (Figure 1), (Note 7) R = 27Ω or 50Ω (Figure 1), (Note 7) −0.2 2 1.5 1.5 −0.2 5 5 5 5 0.2 3 0.2 V V V V V V V Parameter Conditions Min Typ Max Units IOSD VINL VINH IIN VTH ∆VTH RIN IIN IRE VOL VO = High, −7V≤VCM ≤+12V VO = Low, −7V ≤VCM ≤+12V DE, DI, RE DE, DI, RE DE, DI −7V ≤ VCM ≤ + 12V VCM = 0 −7V ≤ VCM ≤ + 12V VIN = 12V VIN = −7V RE IOL = 4mA −250 −250 250 250 0.8 mA V V 2 −1 −0.2 70 12 1 −0.8 −1 1 0.4 1 +0.2 µA V mV kΩ mA µA V Receiver Section 3 www.national.com LMS1485 Electrical Characteristics Symbol VOH IOSR IOZ Parameter CMOS High-Level Output Voltage Short-Circuit Output Current Tristate Output Leakage Current Supply Current (Continued) Over recommended ranges of supply voltage and operating free-air temperature (unless otherwise noted) Conditions IOH = −4mA VO = GND or VCC 0.4V ≤VO ≤+2.4V Min 4 7 −1 85 1 Typ Max Units V mA µA Power Supply Current ICC Driver Enabled, Output = No Load, Digital Inputs = GND or VCC Driver Disabled, Output = No Load, Digital Inputs = GND or VCC Switching Characteristics Driver TPLH, TPHL TSKEW TR, TF TENABLE TDISABLE Receiver TPLH, TPHL TSKEW TENABLE TDISABLE Propagation Delay Input to Output Receiver Output Skew Receiver Enable Time Receiver Disable Time CL = 15pF (Figure 5, Figure 7) (Figure 5, Figure 7) (Figure 6, Figure 10) (Figure 6, Figure 10) 18 33 2 6 15 25 25 55 ns ns ns ns Propagation Delay Input to Output Driver Output Skew Driver Rise and Fall Time Driver Enable to Ouput Valid Time Output Disable Time RL = 54Ω, CL = 100pF (Figure 3, Figure 7) RL = 54Ω, CL = 100pF (Figure 3, Figure 7) RL = 100Ω, CL = 100pF (Figure 3, Figure 7) (Figure 4, Figure 8) (Figure 4, Figure 8) 11 1 5 18 20 10 32 40 20 ns ns ns ns ns 1.1 1 2.2 2.2 mA mA 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 Characteristics 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 TJ(MAX), θJA, and TA. The maximum allowable power dissipation at any ambient temperature is PD = (TJ(MAX) - TA)/θJA. All numbers apply for packages soldered directly into a PC board. Note 4: ESD rating based upon human body model, 100pF discharged through 1.5kΩ. 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 VOD and VOC, respectively when the input changes from high to low levels. Note 8: ESD rating applies to pins 6 and 7 Note 9: ESD rating applies to pins 1, 2, 3, 4, 5 and 8 www.national.com 4 LMS1485 Typical Performance Characteristics Receiver Output Low Voltage vs. Output Current Receiver Output High Voltage vs. Output Current 20048813 20048814 Receiver Output High Voltage vs. Temperature Receiver Output Low Voltage vs. Temperature 20048815 20048816 Driver Differential Output Voltage vs. Output Current Driver Differential Output Voltage vs. Temperature RL = 54Ω 20048817 20048818 5 www.national.com LMS1485 Typical Performance Characteristics Driver Output Low Voltage vs. Output Current (Continued) Driver Output High Voltage vs. Output Current 20048819 20048820 Supply Current vs. Temperature Receiver Skew vs. Temperature 20048821 20048822 Driver Skew vs. Temperature 20048823 www.national.com 6 LMS1485 Parameter Measuring Information 20048803 FIGURE 1. Test Circuit for VOD and VOC 20048804 FIGURE 2. Test Circuit for VOD3 20048805 FIGURE 3. Test Circuit for Driver Propagation Delay 20048806 FIGURE 4. Test Circuit for Driver Enable / Disable 20048807 FIGURE 5. Test Circuit for Receiver Propagation Delay 7 www.national.com LMS1485 Parameter Measuring Information (Continued) 20048808 FIGURE 6. Test Circuit for Receiver Enable / Disable Switching Characteristics 20048811 20048809 FIGURE 9. Receiver Propagation Delay FIGURE 7. Driver Propagation Delay, Rise / Fall Time 20048812 20048810 FIGURE 10. Receiver Enable / Disable Time FIGURE 8. Driver Enable / Disable Time www.national.com 8 LMS1485 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 (Cbp) between the power and ground lines. Placing a by-pass capacitor (Cbp) with the correct value at the proper location solves many power supply noise problems. 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. 20048824 FIGURE 11. Placement of by-pass Capacitors, Cbp 9 www.national.com LMS1485 5V Low Power RS-485 Differential Bus Transceiver Physical Dimensions inches (millimeters) unless otherwise noted 8-Pin SOIC NS Package Number M08A LIFE SUPPORT POLICY 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. National Semiconductor Americas Customer Support Center Email: new.feedback@nsc.com Tel: 1-800-272-9959 www.national.com 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 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 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 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.