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TL/F/12040

DS36C278 Low Power Multipoint EIA-RS-485 Transceiver

December 1995

DS36C278

Low Power Multipoint EIA-RS-485 Transceiver

General Description

The DS36C278 is a low power differential bus/line trans-

ceiver designed to meet the requirements of RS-485 stan-

dard for multipoint data transmission. In addition it is com-

patible with TIA/EIA-422-B.

The CMOS design offers significant power savings over its

bipolar and ALS counterparts without sacrificing ruggedness

against ESD damage. The device is ideal for use in battery

powered or power conscious applications. I

is specified at

500 mA maximum.

The driver and receiver outputs feature TRI-STATE

capa-

bility. The driver outputs operate over the entire common

mode range of

7V to

12V. Bus contention or fault situa-

tions that cause excessive power dissipation within the de-

vice are handled by a thermal shutdown circuit, which forces

the driver outputs into the high impedance state.

The receiver incorporates a fail safe circuit which guaran-

tees a high output state when the inputs are left open.

The DS36C278T is fully specified over the industrial temper-

ature range (

Cto

C).

Features

100% RS-485 compliant

Ð Guaranteed RS-485 device interoperation

Low power CMOS design I

500 mA max

Built-in power up/down glitch-free circuitry

Ð Permits live transceiver insertion/displacement

DIP and SOIC packages available

Industrial temperature range

Cto

On-board thermal shutdown circuitry

Ð Prevents damage to the device in the event of ex-

cessive power dissipation

Wide common mode range

7V to

12V

Receiver open input fail-safe

(/4 unit load (DS36C278)

128 nodes

(/2 unit load (DS36C278T)

64 nodes

ESD (human body model)

2kV

Drop in replacement for:

Ð LTC485, MAX485, DS75176, DS3695

Connection and Logic Diagram

TL/F/12040– 1

Order Number DS36C278TM, DS36C278TN,

DS36C278M, DS36C278N

See NS Package Number M08A or N08E

Truth Table

DRIVER SECTION

RE* DE DI DO/RI DO*/RI*

XHH H L

XHL L H

XLX Z Z

RECEIVER SECTION

RE* DE RI-RI* RO

0.2V H

0.2V L

HL X Z

L L OPEN

Note: Non-terminated, open input only

TRI-STATE

is a registered trademark of National Semiconductor Corporation.

1996 National Semiconductor Corporation RRD-B30M36/Printed in U. S. A.

http://www.national.com

Summary of content (10 pages)

PAGE 1
DS36C278 Low Power Multipoint EIA-RS-485 Transceiver General Description Features The DS36C278 is a low power differential bus/line transceiver designed to meet the requirements of RS-485 standard for multipoint data transmission. In addition it is compatible with TIA/EIA-422-B. The CMOS design offers significant power savings over its bipolar and ALS counterparts without sacrificing ruggedness against ESD damage. The device is ideal for use in battery powered or power conscious applications.
PAGE 2
Absolute Maximum Ratings (Note 1) Recommended Operating Conditions If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/Distributors for availability and specifications. Supply Voltage (VCC) Min Typ Supply Voltage (VCC) a 4.75 a 5.0 b7 Bus Voltage Operating Free Air Temperature (Ta) b 40 DS36C278T 25 DS36C278 0 25 a 12V b 0.5V to (VCC a 0.
PAGE 3
Electrical Characteristics (Continued) Over Supply Voltage and Operating Temperature ranges, unless otherwise specified (Notes 2 and 3) Symbol IIN IING Parameter Line Input Current (Note 7) Line Input Current Glitch (Note 7) Conditions Other Input e 0V, DS36C278 DE e VIL, RE* e VIL, VCC e 4.75 to 5.25 DS36C278T or 0V Other Input e 0V, DS36C278 DE e VIL, RE* e VIL, VCC e a 3.0V or 0V, DS36C278T TA e 25§ C IB Input Balance Test RS e 500X VOH High Level Output Voltage IOH e b4 mA, VID e a 0.
PAGE 4
Switching Characteristics (Continued) Over Supply Voltage and Operating Temperature ranges, unless otherwise specified (Notes 3 and 8) Symbol Parameter Conditions Reference Min Typ Max Units 30 210 400 ns 30 190 400 ns 0 20 50 ns Ð 50 150 ns Ð 55 150 ns Ð 40 150 ns Ð 45 150 ns RECEIVER CHARACTERISTICS tPHL Propagation Delay High to Low tPLH Propagation Delay Low to High tSK Skew, ltPHL b tPLHl tPLZ Output Disable Time CL e 15 pF Figures 12, 13 CL e 15 pF tPHZ t
PAGE 5
Parameter Measurement Information (Continued) TL/F/12040 – 6 FIGURE 6. Driver Differential Propagation Delays and Differential Rise and Fall Times TL/F/12040 – 8 FIGURE 8. TRI-STATE Waveforms (tPZH, tPHZ) TL/F/12040 – 7 FIGURE 7. TRI-STATE Test Circuit (tPZH , tPHZ) TL/F/12040 – 10 FIGURE 10. TRI-STATE Waveforms (tPZL, tPLZ) TL/F/12040 – 9 FIGURE 9. TRI-STATE Test Circuit (tPZL, tPLZ) TL/F/12040 – 12 FIGURE 12. Receiver Differential Propagation Delay Test Circuit TL/F/12040 – 11 FIGURE 11.
PAGE 6
Parameter Measurement Information (Continued) TL/F/12040 – 13 FIGURE 13. Receiver Differential Propagation Delay Waveforms TL/F/12040 – 14 FIGURE 14. Receiver TRI-STATE Test Circuit TL/F/12040 – 15 FIGURE 15. Receiver Enable and Disable Waveforms (tPLZ, tPZL) TL/F/12040 – 16 FIGURE 16. Receiver Enable and Disable Waveforms (tPHZ, tPZH) http://www.national.
PAGE 7
Typical Application Information TL/F/12040 – 17 FIGURE 17. Typical RS-485 Bus Interface TABLE I. Device Pin Descriptions Pin No. Name Description 1 RO Receiver Output: When RE (Receiver Enable) is LOW, the receiver is enabled (ON), if DO/RI t DO*/RI* by 200 mV, RO will be HIGH. If DO/RI s DO*/RI* by 200 mV, RO will be LOW. Additionally RO will be HIGH for OPEN (Non-terminated) Inputs. 2 RE* Receiver Output Enable: When RE* is LOW the receiver output is enabled.
PAGE 8
http://www.national.
PAGE 9
Physical Dimensions inches (millimeters) 8-Lead (0.150× Wide) Molded Small Outline Package, JEDEC Order Number DS36C278TM, DS36C278M NS Package Number M08A 9 http://www.national.
PAGE 10
DS36C278 Low Power Multipoint EIA-RS-485 Transceiver Physical Dimensions inches (millimeters) (Continued) 8-Lead (0.300× Wide) Molded Dual-In-Line Package Order Number DS36C278TN, DS36C278N NS Package Number N08E 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 OF NATIONAL SEMICONDUCTOR CORPORATION. As used herein: 1.