DS36C278
DS36C278 Low Power Multipoint EIA-RS-485 Transceiver
Literature Number: SNLS096B
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
CC
is specified at
500 µA 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 guarantees
a high output state when the inputs are left open. (Note 1)
The DS36C278T is fully specified over the industrial tem-
perature range (−40˚C to +85˚C).
Features
n100% RS-485 compliant
— Guaranteed RS-485 device interoperation
nLow power CMOS design: I
CC
500 µA max
nBuilt-in power up/down glitch-free circuitry
— Permits live transceiver insertion/displacement
nDIP and SOIC packages available
nIndustrial temperature range: −40˚C to +85˚C
nOn-board thermal shutdown circuitry
— Prevents damage to the device in the event of
excessive power dissipation
nWide common mode range: −7V to +12V
nReceiver open input fail-safe (Note 1)
n
1
⁄
4
unit load (DS36C278): ≥128 nodes
n
1
⁄
2
unit load (DS36C278T): ≥64 nodes
nESD (human body model): ≥2kV
nDrop in replacement for:
— LTC485, MAX485, DS75176, DS3695
Connection Diagram
01204001
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
LL ≥+0.2V H
LL ≤−0.2V L
HL X Z
L L OPEN (Note 1) H
Note 1: Non-terminated, open input only
TRI-STATE®is a registered trademark of National Semiconductor Corporation.
July 1998
DS36C278 Low Power Multipoint EIA-RS-485 Transceiver
© 2004 National Semiconductor Corporation DS012040 www.national.com
Absolute Maximum Ratings (Note 2)
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
Supply Voltage (V
CC
) +12V
Input Voltage (DE, RE*, & DI) −0.5V to (V
CC
+0.5V)
Common Mode (V
CM
)
Driver Output/Receiver Input ±15V
Input Voltage (DO/RI, DO*/RI*) ±14V
Receiver Output Voltage −0.5V to (V
CC
+0.5V)
Maximum Package Power Dissipation
@+25˚C
M Package 1190 mW, derate 9.5 mW/˚C above
+25˚C
N Package 744 mW, derate 6.0 mW/˚C above
+25˚C
Storage Temperature Range −65˚C to +150˚C
Lead Temperature
(Soldering 4 sec) +260˚C
Recommended Operating
Conditions
Min Typ Max Units
Supply Voltage (V
CC
) +4.75 +5.0 +5.25 V
Bus Voltage −7 +12 V
Operating Free Air Temperature (Ta)
DS36C278T −40 25 +85 ˚C
DS36C278 0 25 +70 ˚C
Electrical Characteristics (Notes 3, 4)
Over Supply Voltage and Operating Temperature ranges, unless otherwise specified
Symbol Parameter Conditions Reference Min Typ Max Units
DIFFERENTIAL DRIVER CHARACTERISTICS
V
OD1
Differential Output Voltage I
O
= 0 mA (No Load) (422)
(485)
1.5 5.0 V
V
OD0
Output Voltage I
O
= 0 mA 0 5.0 V
V
OD0*
Output Voltage (Output to GND) 0 5.0 V
V
OD2
Differential Output Voltage R
L
=50Ω(422) Figure 1 2.0 2.8 V
(Termination Load) R
L
=27Ω(485) 1.5 2.3 5.0 V
∆V
OD2
Balance of V
OD2
R
L
=27Ωor 50Ω(Note 5) −0.2 0.1 +0.2 V
|V
OD2
−V
0D2*
| (422, 485)
V
OD3
Differential Output Voltage
(Full Load)
R1=54Ω,R2=375Ω
V
TEST
= −7V to +12V Figure 2 1.5 2.0 5.0 V
V
OC
Driver Common Mode
Output Voltage
R
L
=27Ω(485) Figure 1 0 3.0 V
R
L
=50Ω(422) 0 3.0 V
∆V
OC
Balance of V
OC
|V
OC
−V
OC*
|
R
L
=27Ωor
R
L
=50Ω
(Note 5)
(422, 485) −0.2 +0.2 V
I
OSD
Driver Output Short-Circuit
Current
V
O
= +12V (485) Figure 4 200 +250 mA
V
O
= −7V (485) −190 −250 mA
RECEIVER CHARACTERISTICS
V
TH
Differential Input High
Threshold Voltage
V
O
=V
OH
,I
O
= −0.4V
−7V ≤V
CM
≤+12V (Note 6)
(422, 485)
+0.035 +0.2 V
V
TL
Differential Input Low
Threshold Voltage
V
O
=V
OL
,I
O
= 0.4 mA
−7V ≤V
CM
≤+12V −0.2 −0.035 V
V
HST
Hysteresis V
CM
= 0V (Note 7) 70 mV
R
IN
Input Resistance −7V ≤V
CM
≤+12V DS36C278T 24 68 kΩ
R
IN
Input Resistance −7V ≤V
CM
≤+12V DS36C278 48 68 kΩ
I
IN
Line Input Current Other Input = 0V, DS36C278 V
IN
= +12V 0 0.19 0.25 mA
(Note 8) DE = V
IL
,RE*=V
IL
,V
IN
= −7V 0 −0.1 −0.2 mA
V
CC
= 4.75 to 5.25 DS36C278T V
IN
= +12V 0 0.19 0.5 mA
or 0V V
IN
= −7V 0 −0.1 −0.4 mA
I
ING
Line Input Current Glitch Other Input = 0V, DS36C278 V
IN
= +12V 0 0.19 0.25 mA
(Note 8) DE = V
IL
,RE*=V
IL
,V
IN
= −7V 0 −0.1 −0.2 mA
V
CC
= +3.0V or 0V, DS36C278T V
IN
= +12V 0 0.19 0.5 mA
T
A
= 25˚C V
IN
= −7V 0 −0.1 −0.4 mA
DS36C278
www.national.com 2
Electrical Characteristics (Notes 3, 4) (Continued)
Over Supply Voltage and Operating Temperature ranges, unless otherwise specified
Symbol Parameter Conditions Reference Min Typ Max Units
RECEIVER CHARACTERISTICS
I
B
Input Balance Test RS = 500Ω(422) (Note 10) ±400 mV
V
OH
High Level Output Voltage I
OH
= −4 mA, V
ID
= +0.2V RO
Figure 11
3.5 4.6 V
V
OL
Low Level Output Voltage I
OL
= +4 mA, V
ID
= −0.2V 0.3 0.5 V
I
OSR
Short Circuit Current V
O
= GND RO 73585mA
I
OZR
TRI-STATE Leakage Current V
O
= 0.4V to 2.4V ±1µA
DEVICE CHARACTERISTICS
V
IH
High Level Input Voltage
DE,
RE*,
DI
2.0 V
CC
V
V
IL
Low Level Input Voltage GND 0.8 V
I
IH
High Level Input Current V
IH
=V
CC
2µA
I
IL
Low Level Input Current V
CC
=5V V
IL
=0V −2 µA
V
CC
= +3.0V −2 µA
I
CC
Power Supply Current Driver and Receiver ON
V
CC
200 500 µA
I
CCR
(No Load) Driver OFF, Receiver ON 200 500 µA
I
CCD
Driver ON, Receiver OFF 200 500 µA
I
CCZ
Driver and Receiver OFF 200 500 µA
Switching Characteristics (Notes 4, 9)
Over Supply Voltage and Operating Temperature ranges, unless otherwise specified
Symbol Parameter Conditions Reference Min Typ Max Units
DRIVER CHARACTERISTICS
t
PHLD
Differential Propagation
Delay High to Low
R
L
=54Ω,C
L
= 100 pF
Figures 5, 6
10 39 80 ns
t
PLHD
Differential Propagation
Delay Low to High 10 40 80 ns
t
SKD
Differential Skew
|t
PHLD
−t
PLHD
|0 1 10 ns
t
r
Rise Time 32550 ns
t
f
Fall Time 32550 ns
t
PHZ
Disable Time High to Z C
L
=15pF Figures 7, 8 — 80 200 ns
t
PLZ
Disable Time Low to Z RE*=L Figures 9, 10 — 80 200 ns
t
PZH
Enable Time Z to High C
L
= 100 pF Figures 7, 8 — 50 200 ns
t
PZL
Enable Time Z to Low RE*=L Figures 9, 10 — 65 200 ns
RECEIVER CHARACTERISTICS
t
PHL
Propagation Delay
High to Low
C
L
=15pF
Figures 12, 13
30 210 400 ns
t
PLH
Propagation Delay
Low to High 30 190 400 ns
t
SK
Skew, |t
PHL
−t
PLH
| 0 20 50 ns
t
PLZ
Output Disable Time C
L
=15pF
Figures 14, 15, 16
— 50 150 ns
t
PHZ
— 55 150 ns
t
PZL
Output Enable Time — 40 150 ns
t
PZH
— 45 150 ns
DS36C278
www.national.com3
Switching Characteristics (Notes 4, 9) (Continued)
Note 2: “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 3: 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 and
VOD2.
Note 4: All typicals are given for: VCC = +5.0V, TA= + 25˚C.
Note 5: Delta |VOD2| and Delta |VOC| are changes in magnitude of VOD2 and VOC, respectively, that occur when input changes state.
Note 6: Threshold parameter limits specified as an algebraic value rather than by magnitude.
Note 7: Hysteresis defined as VHST =V
TH −V
TL.
Note 8: IIN includes the receiver input current and driver TRI-STATE leakage current.
Note 9: CLincludes probe and jig capacitance.
Note 10: For complete details of test, see RS-485.
Parameter Measurement Information
01204002
FIGURE 1. Driver V
OD2
and V
OC
01204018
FIGURE 2. Driver V
OD3
01204003
FIGURE 3. Driver V
OH
and V
OL
01204004
Vtest = −7V to +12V
FIGURE 4. Driver I
OSD
01204005
FIGURE 5. Driver Differential Propagation Delay Test
Circuit
01204006
FIGURE 6. Driver Differential Propagation Delays and
Differential Rise and Fall Times
DS36C278
www.national.com 4
Parameter Measurement
Information (Continued)
01204007
FIGURE 7. TRI-STATE Test Circuit (t
PZH
,t
PHZ
)
01204008
FIGURE 8. TRI-STATE Waveforms (t
PZH
,t
PHZ
)
01204009
FIGURE 9. TRI-STATE Test Circuit (t
PZL
,t
PLZ
)
01204010
FIGURE 10. TRI-STATE Waveforms (t
PZL
,t
PLZ
)
01204011
FIGURE 11. Receiver V
OH
and V
OL
01204012
FIGURE 12. Receiver Differential Propagation Delay
Test Circuit
01204013
FIGURE 13. Receiver Differential Propagation Delay
Waveforms
DS36C278
www.national.com5
Parameter Measurement Information (Continued)
01204014
FIGURE 14. Receiver TRI-STATE Test Circuit
01204015
FIGURE 15. Receiver Enable and Disable Waveforms (t
PLZ
,t
PZL
)
01204016
FIGURE 16. Receiver Enable and Disable Waveforms (t
PHZ
,t
PZH
)
DS36C278
www.national.com 6
Typical Application Information
TABLE 1. 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 ≥DO*/RI*
by 200 mV, RO will be HIGH. If DO/RI ≤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. When RE* is HIGH, the
receiver output is in TRI-STATE (OFF).
3 DE Driver Output Enable: When DE is HIGH, the driver outputs are enabled. When DE is LOW, the driver
outputs are in TRI-STATE (OFF).
4 DI Driver Input: When DE (Driver Enable) is HIGH, the driver is enabled, if DI is LOW, then DO/RI will be
LOW and DO*/RI* will be HIGH. If DI is HIGH, then DO/RI is HIGH and DO*/RI* is LOW.
5 GND Ground Connection.
6 DO/RI Driver Output/Receiver Input, 485 Bus Pin.
7 DO*/RI* Driver Output/Receiver Input, 485 Bus Pin.
8V
CC
Positive Power Supply Connection: Recommended operating range for V
CC
is +4.75V to +5.25V.
Unit Load
A unit load for an RS-485 receiver is defined by the input
current versus the input voltage curve. The gray shaded
region is the defined operating range from −7V to +12V. The
top border extending from −3V at 0 mA to +12V at +1 mA is
defined as one unit load. Likewise, the bottom border ex-
tending from +5V at 0 mA to −7V at −0.8 mA is also defined
as one unit load (see Figure 18 ). An RS-485 driver is
capable of driving up to 32 unit loads. This allows up to 32
nodes on a single bus. Although sufficient for many applica-
tions, it is sometimes desirable to have even more nodes.
For example, an aircraft that has 32 rows with 4 seats per
row would benefit from having 128 nodes on one bus. This
would allow signals to be transferred to and from each
individual seat to 1 main station. Usually there is one or two
less seats in the last row of the aircraft near the restrooms
and food storage area. This frees the node for the main
station.
The DS36C278, the DS36C279, and the DS36C280 all have
1
⁄
2
unit load and
1
⁄
4
unit load (UL) options available. These
devices will allow up to 64 nodes or 128 nodes guaranteed
over temperature depending upon which option is selected.
The
1
⁄
2
UL option is available in industrial temperature and
the
1
⁄
4
UL is available in commercial temperature.
First, for a
1
⁄
2
UL device the top and bottom borders shown in
Figure 18 are scaled. Both 0 mA reference points at +5V and
−3V stay the same. The other reference points are +12V at
+0.5 mA for the top border and −7V at −0.4 mA for the
bottom border (see Figure 18 ). Second, for a
1
⁄
4
UL device
the top and bottom borders shown in Figure 18 are scaled
also. Again, both 0 mA reference points at +5V and −3V stay
the same. The other reference points are +12V at +0.25 mA
for the top border and −7V at −0.2 mA for the bottom border
(see Figure 18 ).
The advantage of the
1
⁄
2
UL and
1
⁄
4
UL devices is the
increased number of nodes on one bus. In a single master
multi-slave type of application where the number of slaves
exceeds 32, the DS36C278/279/280 may save in the cost of
extra devices like repeaters, extra media like cable, and/or
extra components like resistors.
The DS36C279 and DS36C280 have an additional feature
which offers more advantages. The DS36C279 has an au-
tomatic sleep mode function for power conscious applica-
tions. The DS36C280 has a slew rate control for EMI con-
scious applications. Refer to the sleep mode and slew rate
control portion of the application information section in the
corresponding datasheet for more information on these
features.
01204017
FIGURE 17. Typical RS-485 Bus Interface
DS36C278
www.national.com7
Unit Load (Continued)
01204019
FIGURE 18. Input Current vs Input Voltage Operating Range
DS36C278
www.national.com 8
Physical Dimensions inches (millimeters)
unless otherwise noted
8-Lead (0.150" Wide) Molded Small Outline Package, JEDEC
Order Number DS36C278TM, DS36C278M
NS Package Number M08A
DS36C278
www.national.com9
Physical Dimensions inches (millimeters) unless otherwise noted (Continued)
8-Lead (0.300" Wide) Molded Dual-In-Line Package
Order Number DS36C278TN, DS36C278N
NS Package Number N08E
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.
For the most current product information visit us at www.national.com.
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.
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.
BANNED SUBSTANCE COMPLIANCE
National Semiconductor certifies that the products and packing materials meet the provisions of the Customer Products Stewardship
Specification (CSP-9-111C2) and the Banned Substances and Materials of Interest Specification (CSP-9-111S2) and contain no ‘‘Banned
Substances’’ as defined in CSP-9-111S2.
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
DS36C278 Low Power Multipoint EIA-RS-485 Transceiver
IMPORTANT NOTICE
Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, modifications, enhancements, improvements,
and other changes to its products and services at any time and to discontinue any product or service without notice. Customers should
obtain the latest relevant information before placing orders and should verify that such information is current and complete. All products are
sold subject to TI’s terms and conditions of sale supplied at the time of order acknowledgment.
TI warrants performance of its hardware products to the specifications applicable at the time of sale in accordance with TI’s standard
warranty. Testing and other quality control techniques are used to the extent TI deems necessary to support this warranty. Except where
mandated by government requirements, testing of all parameters of each product is not necessarily performed.
TI assumes no liability for applications assistance or customer product design. Customers are responsible for their products and
applications using TI components. To minimize the risks associated with customer products and applications, customers should provide
adequate design and operating safeguards.
TI does not warrant or represent that any license, either express or implied, is granted under any TI patent right, copyright, mask work right,
or other TI intellectual property right relating to any combination, machine, or process in which TI products or services are used. Information
published by TI regarding third-party products or services does not constitute a license from TI to use such products or services or a
warranty or endorsement thereof. Use of such information may require a license from a third party under the patents or other intellectual
property of the third party, or a license from TI under the patents or other intellectual property of TI.
Reproduction of TI information in TI data books or data sheets is permissible only if reproduction is without alteration and is accompanied
by all associated warranties, conditions, limitations, and notices. Reproduction of this information with alteration is an unfair and deceptive
business practice. TI is not responsible or liable for such altered documentation. Information of third parties may be subject to additional
restrictions.
Resale of TI products or services with statements different from or beyond the parameters stated by TI for that product or service voids all
express and any implied warranties for the associated TI product or service and is an unfair and deceptive business practice. TI is not
responsible or liable for any such statements.
TI products are not authorized for use in safety-critical applications (such as life support) where a failure of the TI product would reasonably
be expected to cause severe personal injury or death, unless officers of the parties have executed an agreement specifically governing
such use. Buyers represent that they have all necessary expertise in the safety and regulatory ramifications of their applications, and
acknowledge and agree that they are solely responsible for all legal, regulatory and safety-related requirements concerning their products
and any use of TI products in such safety-critical applications, notwithstanding any applications-related information or support that may be
provided by TI. Further, Buyers must fully indemnify TI and its representatives against any damages arising out of the use of TI products in
such safety-critical applications.
TI products are neither designed nor intended for use in military/aerospace applications or environments unless the TI products are
specifically designated by TI as military-grade or "enhanced plastic."Only products designated by TI as military-grade meet military
specifications. Buyers acknowledge and agree that any such use of TI products which TI has not designated as military-grade is solely at
the Buyer's risk, and that they are solely responsible for compliance with all legal and regulatory requirements in connection with such use.
TI products are neither designed nor intended for use in automotive applications or environments unless the specific TI products are
designated by TI as compliant with ISO/TS 16949 requirements. Buyers acknowledge and agree that, if they use any non-designated
products in automotive applications, TI will not be responsible for any failure to meet such requirements.
Following are URLs where you can obtain information on other Texas Instruments products and application solutions:
Products Applications
Audio www.ti.com/audio Communications and Telecom www.ti.com/communications
Amplifiers amplifier.ti.com Computers and Peripherals www.ti.com/computers
Data Converters dataconverter.ti.com Consumer Electronics www.ti.com/consumer-apps
DLP®Products www.dlp.com Energy and Lighting www.ti.com/energy
DSP dsp.ti.com Industrial www.ti.com/industrial
Clocks and Timers www.ti.com/clocks Medical www.ti.com/medical
Interface interface.ti.com Security www.ti.com/security
Logic logic.ti.com Space, Avionics and Defense www.ti.com/space-avionics-defense
Power Mgmt power.ti.com Transportation and Automotive www.ti.com/automotive
Microcontrollers microcontroller.ti.com Video and Imaging www.ti.com/video
RFID www.ti-rfid.com
OMAP Mobile Processors www.ti.com/omap
Wireless Connectivity www.ti.com/wirelessconnectivity
TI E2E Community Home Page e2e.ti.com
Mailing Address: Texas Instruments, Post Office Box 655303, Dallas, Texas 75265
Copyright ©2011, Texas Instruments Incorporated
