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串口RS422、RS485多点通信资料.pdf

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    / D S 7 5 1 7 6 B D S 7 5 1 7 6 B T M u l t i p o n t i R S - 4 8 5 R S - 4 2 2 / T r a n s c e i v e r s July 1998 DS75176B/DS75176BT Multipoint RS-485/RS-422 Transceivers General Description The DS75176B is a high speed differential TRI-STATE® bus/line transceiver designed to meet the requirements of EIA standard RS485 with extended common mode range (+12V to −7V), for multipoint data transmission. In addition, it is compatible with RS-422. The driver and receiver outputs feature TRI-STATE capabil- ity, for the driver outputs over the entire common mode range of +12V to −7V. Bus contention or fault situations that cause excessive power dissipation within the device are handled by a thermal shutdown circuit, which forces the driver outputs into the high impedance state. DC specifications are guaranteed over the 0 to 70˚C tem- perature and 4.75V to 5.25V supply voltage range. n 22 ns driver propagation delays. n Single +5V supply. n −7V to +12V bus common mode range permits ±7V ground difference between devices on the bus. n Thermal shutdown protection. n High impedance to bus with driver in TRI-STATE or with power off, over the entire common mode range allows the unused devices on the bus to be powered down. n Pin out compatible with DS3695/A and SN75176A/B. n Combined impedance of a driver output and receiver Features n Meets EIA standard RS485 for multipoint bus transmission and is compatible with RS-422. n Small Outline (SO) Package option available for minimum board space. Connection and Logic Diagram input is less than one RS485 unit load, allowing up to 32 transceivers on the bus. n 70 mV typical receiver hysteresis. Order Number DS75176BN, DS75176BTN, DS75176BM or DS75176BTM See NS Package Number N08E or M08A DS008759-1 Top View TRI-STATE® is a registered trademark of National Semiconductor Corp. © 1999 National Semiconductor Corporation DS008759 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, VCC Control Input Voltages Driver Input Voltage Driver Output Voltages Receiver Input Voltages (DS75176B) Receiver Output Voltage Continuous Power Dissipation @ 25˚C for M Package for N Package Storage Temperature Range Lead Temperature (Soldering, 4 seconds) 7V 7V 7V +15V/ −10V +15V/ −10V 5.5V 675 mW (Note 5) 900 mW (Note 4) −65˚C to +150˚C 260˚C Recommended Operating Conditions Supply Voltage, VCC Voltage at Any Bus Terminal (Separate or Common Mode) Operating Free Air Temperature TA DS75176B DS75176BT Differential Input Voltage, VID (Note 6) Min Max Units 4.75 −7 5.25 +12 V V 0 −40 +70 +85 −12 +12 ˚C ˚C V Electrical Characteristics (Notes 2, 3) 0˚C £ TA£ 70˚C, 4.75V < VCC< 5.25V unless otherwise specified Symbol VOD1 IO = 0 Parameter Differential Driver Output Voltage (Unloaded) Differential Driver Output Voltage (with Load) Change in Magnitude of Driver Differential Output Voltage For Complementary Output States Driver Common Mode Output Voltage Change in Magnitude of Driver Common Mode Output Voltage For Complementary Output States Input High Voltage Input Low Voltage Input Clamp Voltage Input Low Current Input High Current Input Current Differential Input Threshold Voltage for Receiver Receiver Input Hysteresis Receiver Output High Voltage Output Low Voltage OFF-State (High Impedance) Output Current at Receiver Receiver Input Resistance Supply Current RO Driver Short-Circuit Output Current DO/RI, DO/RI Conditions Min Typ Max Units (Figure1) R = 50W R = 27W ; (RS-422) (Note 7) ; (RS-485) 2 1.5 (Figure1) R = 27W DI, DE, RE , E VCC = 0V or 5.25V DE = 0V −7V £ VCM £ + 12V VCM = 0V IOH = −400 µA IOL = 16 mA (Note 7) VCC = Max 0.4V £ VO £ 2.4V −7V £ VCM £ +12V No Load (Note 7) VO = −7V (Note 7) VO = +12V (Note 7) IIN = −18 mA VIL = 0.4V VIH = 2.4V VIN = 12V VIN = −7V Driver Outputs Enabled Driver Outputs Disabled 2 −0.2 2.7 12 5 0.2 3.0 0.2 V V V V V V V 70 0.8 −1.5 µA −200 20 µA +1.0 mA −0.8 mA +0.2 V mV V V µA 0.5 ±20 55 35 kW mA mA −250 mA +250 mA VOD2 D VOD VOC |VOC| VIH VIL VCL IIL IIH IIN VTH D VTH VOH VOL IOZR RIN ICC IOSD www.national.com 2 D
    Electrical Characteristics (Notes 2, 3) (Continued) 0˚C £ TA£ 70˚C, 4.75V < VCC< 5.25V unless otherwise specified Symbol IOSR Parameter Receiver Short-Circuit Output Current VO = 0V Conditions Min Typ Max Units −15 −85 mA Note 1: “Absolute Maximum Ratings” are those beyond which the safety of the device cannot be guaranteed. They are not meant to imply that the device should be operated at these limits. The tables of “Electrical Characteristics” provide conditions for actual device operation. Note 2: All currents into device pins are positive; all currents out of device pins are negative. All voltages are referenced to device ground unless otherwise specified. Note 3: All typicals are given for VCC = 5V and TA = 25˚C. Note 4: Derate linearly at 5.56 mW/˚C to 650 mW at 70˚C. Note 5: Derate linearly 6.11 mW/˚C to 400 mW at 70˚C. Note 6: Differential - Input/Output bus voltage is measured at the noninverting terminal A with respect to the inverting terminal B. Note 7: All worst case parameters for which note 7 is applied, must be increased by 10% for DS75176BT. The other parameters remain valid for −40˚C < TA < +85˚C. Switching Characteristics VCC = 5.0V, TA = 25˚C Symbol tPLH tPHL tr tf Parameter Driver Input to Output Driver Input to Output Driver Rise Time Driver Fall Time tZH tZL tLZ tHZ tPLH tPHL tZL tZH tLZ tHZ Driver Enable to Output High Driver Enable to Output Low Driver Disable Time from Low Driver Disable Time from High Receiver Input to Output Receiver Input to Output Receiver Enable to Output Low Receiver Enable to Output High Receiver Disable from Low Receiver Disable from High Conditions Min RLDIFF = 60W CL1 = CL2 = 100 pF RLDIFF = 60W CL1 =CL2 = 100 pF (Figure3 and Figure5) CL = 100 pF (Figure4 and Figure6) S1 Open CL = 100 pF (Figure4 and Figure6) S2 Open CL = 15 pF (Figure4 and Figure6) S2 Open CL = 15 pF (Figure4 and Figure6) S1 Open CL = 15 pF (Figure2 and Figure7) S1 and S2 Closed CL = 15 pF (Figure2 and Figure8) S2 Open CL = 15 pF (Figure2 and Figure8) S1 Open CL = 15 pF (Figure2 and Figure8) S2 Open CL = 15 pF (Figure2 and Figure8) S1 Open Typ 12 17 29 31 13 19 30 32 15 11 28 13 Max 22 22 18 18 100 60 30 200 37 37 20 20 32 35 Units ns ns ns ns ns ns ns ns ns ns ns ns ns ns 3 www.national.com
    AC Test Circuits DS008759-2 FIGURE 1. Note: S1 and S2 of load circuit are closed except as otherwise mentioned. DS008759-3 FIGURE 2. FIGURE 3. DS008759-4 Switching Time Waveforms Note: Unless otherwise specified the switches are closed. DS008759-5 FIGURE 4. FIGURE 5. Driver Propagation Delays and Transition Times DS008759-6 www.national.com 4
    Switching Time Waveforms (Continued) FIGURE 6. Driver Enable and Disable Times DS008759-7 Note: Differential input voltage may may be realized by grounding RI and pulsing RI between +2.5V and −2.5V FIGURE 7. Receiver Propagation Delays DS008759-8 FIGURE 8. Receiver Enable and Disable Times DS008759-9 Function Tables DS75176B Transmitting Inputs DE 1 1 0 1 RE X X X X DI 1 0 X X Outputs DO 0 1 Z Z DO 1 0 Z Z Line Condition No Fault No Fault X Fault 5 www.national.com
    Function Tables (Continued) DS75176B Receiving Inputs Outputs RE 0 0 0 1 DE 0 0 0 0 RI-RI ‡ +0.2V £ −0.2V Inputs Open** X RO 1 0 1 Z X — Don’t care condition Z — High impedance state Fault — Improper line conditons causing excessive power dissipation in the driver, such as shorts or bus contention situations **This is a fail safe condition Typical Application DS008759-11 www.national.com 6
    Physical Dimensions inches (millimeters) unless otherwise noted Lit. # 103669 Molded Dual-In-Line Package (N) Order Number DS75176BN or DS75176BTN NS Package Number N08E 7 www.national.com
    s r e v i e c s n a r T 2 2 4 - S R 5 8 4 - S R / i t n o p i t l u M T B 6 7 1 5 7 S D B 6 7 1 5 7 S D / 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- 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 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.
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