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DS36C278
Low Power Multipoint EIA-RS-485 Transceiver
DS36C278 Low Power Multipoint EIA-RS-485 Transceiver
December 1995
General Description
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. I
500 mA maximum.
The driver and receiver outputs feature TRI-STATE
bility. The driver outputs operate over the entire common
mode range of
b
7V toa12V. Bus contention or fault situa-
is specified at
CC
É
capa-
tions 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.
The receiver incorporates a fail safe circuit which guarantees a high output state when the inputs are left open.
The DS36C278T is fully specified over the industrial temperature range (
b
40§Ctoa85§C).
²
Connection and Logic Diagram
Order Number DS36C278TM, DS36C278TN,
DS36C278M, DS36C278N
See NS Package Number M08A or N08E
TL/F/12040– 1
Features
Y
100% RS-485 compliant
Ð Guaranteed RS-485 device interoperation
Y
Low power CMOS design ICC500 mA max
Y
Built-in power up/down glitch-free circuitry
Ð Permits live transceiver insertion/displacement
Y
DIP and SOIC packages available
Y
Industrial temperature range
Y
On-board thermal shutdown circuitry
b
40§Ctoa85§C
Ð Prevents damage to the device in the event of ex-
cessive power dissipation
Y
Wide common mode range
Y
Receiver open input fail-safe
Y
(/4 unit load (DS36C278)
Y
(/2 unit load (DS36C278T)
Y
ESD (human body model)
Y
Drop in replacement for:
²
b
7V toa12V
t
128 nodes
t
64 nodes
Ð LTC485, MAX485, DS75176, DS3695
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
t
LL
LL
HL X Z
L L OPEN
²
Note: Non-terminated, open input only
a
0.2V H
s
b
0.2V L
²
H
t
2kV
TRI-STATEÉis a registered trademark of National Semiconductor Corporation.
C
1996 National Semiconductor Corporation RRD-B30M36/Printed in U. S. A.
TL/F/12040
http://www.national.com
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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
Input Voltage (DE, RE*, & DI)
Common Mode (V
CC
CM
)
b
0.5V to (V
)
Driver Output/Receiver Input
Input Voltage (DO/RI, DO*/RI*)
Receiver Output Voltage
Maximum Package Power Dissipation
@
a
25§C
M Package 1190 mW, derate 9.5 mW/
N Package 744 mW, derate 6.0 mW/
Storage Temperature Range
b
0.5V to (V
C abovea25§C
§
C abovea25§C
§
b
65§Ctoa150§C
Lead Temperature (Soldering 4 sec)
CC
CC
a
a
a
a
12V
0.5V)
g
15V
g
14V
0.5V)
260§C
Recommended Operating
Conditions
Supply Voltage (V
Bus Voltage
Operating Free Air Temperature (Ta)
DS36C278T
DS36C278 0 25
Min Typ Max Units
)a4.75a5.0a5.25 V
CC
b
7
b
40 25
a
12 V
a
85§C
a
70§C
Electrical Characteristics
Over Supply Voltage and Operating Temperature ranges, unless otherwise specified (Notes 2 and 3)
Symbol Parameter Conditions Reference Min Typ Max Units
DIFFERENTIAL DRIVER CHARACTERISTICS
V
V
V
V
DV
V
V
DV
I
OSD
OD1
OD0
OD0*
OD2
OD3
OC
Differential Output Voltage I
Output Voltage I
Output Voltage (Output to GND) 0 5.0 V
Differential Output Voltage R
(Termination Load)
Balance of V
OD2
V
l
OD2
OD2
b
V
l
OD2*
Differential Output Voltage R1e54X,R2e375X
(Full Load) V
Driver Common Mode R
Output Voltage
Balance of V
OC
V
l
OC
OC
b
V
l
OC*
Driver Output Short-Circuit V
Current
RECEIVER CHARACTERISTICS
V
TH
V
TL
V
HST
R
IN
R
IN
Differential Input High V
Threshold Voltage
Differential Input Low V
Threshold Voltage
Hysteresis V
Input Resistance
Input Resistance
e
0 mA (No Load)
O
e
0 mA 0 5.0 V
O
e
50X (422)
L
e
R
27X (485) 1.5 2.3 5.0 V
L
e
R
27X or 50X (Note 4)
L
eb
TEST
L
R
L
R
L
R
L
O
V
O
O
b
7VsV
O
b
7VsV
CM
b
7VsV
b
7VsV
7V toa12V
e
27X (485)
e
50X (422) 0 3.0 V
e
27X or (Note 4)
e
50X (422, 485)
ea
12V (485)
eb
7V (485)
e
e
eb
VOH,I
CM
VOL,I
CM
e
0V (Note 6) 70 mV
CM
CM
0.4V
O
s
a
12V
e
0.4 mA
O
s
a
12V
s
a
12V DS36C278T 24 68 kX
s
a
12V DS36C278 48 68 kX
(422)
(485)
Figure 1
(422, 485)
Figure 2
Figure 1
Figure 4
(Note 5)
(422, 485)
1.5 5.0 V
2.0 2.8 V
b
0.2 0.1
1.5 2.0 5.0 V
0 3.0 V
b
0.2
200
b
190
a
0.035
b
0.2b0.035 V
a
0.2 V
a
0.2 V
a
250 mA
b
250 mA
a
0.2 V
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Page 3
Electrical Characteristics (Continued)
Over Supply Voltage and Operating Temperature ranges, unless otherwise specified (Notes 2 and 3)
Symbol Parameter Conditions Reference Min Typ Max Units
I
I
I
V
V
I
I
Line Input Current Other Inpute0V, DS36C278 V
IN
Line Input Current Glitch Other Inpute0V, DS36C278 V
ING
Input Balance Test RSe500X (422) (Note 9)
B
High Level Output Voltage I
OH
Low Level Output Voltage I
OL
Short Circuit Current V
OSR
TRI-STATE Leakage Current V
OZR
DEVICE CHARACTERISTICS
V
V
I
I
I
I
I
I
High Level Input Voltage
IH
Low Level Input Voltage GND 0.8 V
IL
High Level Input Current V
IH
Low Level Input Current V
IL
Power Supply Current Driver and Receiver ON
CC
(No Load)
CCR
CCD
CCZ
DEeVIL,RE*eVIL,(Note 7)
e
V
4.75 to 5.25
CC
or 0V
DS36C278T
DEeVIL,RE*eVIL,(Note 7)
ea
V
T
V
OH
OL
CC
A
O
O
IH
CC
CC
e
eb
ea
e
e
e
3.0V or 0V,
25§C
4 mA, V
4 mA, V
GND
0.4V to 2.4V
V
CC
e
5V
ea
3.0V
DS36C278T V
ea
0.2V
ID
eb
0.2V 0.3 0.5 V
ID
e
0V
V
IL
Driver OFF, Receiver ON 200 500 mA
Driver ON, Receiver OFF 200 500 mA
Driver and Receiver OFF 200 500 mA
ea
12V 0 0.19 0.25 mA
IN
eb
V
7V 0b0.1b0.2 mA
IN
ea
V
12V 0 0.19 0.5 mA
IN
eb
V
7V 0b0.1b0.4 mA
IN
ea
12V 0 0.19 0.25 mA
IN
eb
V
7V 0b0.1b0.2 mA
IN
ea
12V 0 0.19 0.5 mA
IN
eb
V
7V 0b0.1b0.4 mA
IN
RO
3.5 4.6 V
Figure 11
RO
73585mA
2.0 V
DE,
RE*,
DI
V
CC
g
400 mV
g
1 mA
CC
2 mA
b
2 mA
b
2 mA
200 500 mA
V
Switching Characteristics
Over Supply Voltage and Operating Temperature ranges, unless otherwise specified (Notes 3 and 8)
Symbol Parameter Conditions Reference Min Typ Max Units
DRIVER CHARACTERISTICS
t
PHLD
t
PLHD
t
SKD
t
r
t
f
t
PHZ
t
PLZ
t
PZH
t
PZL
Differential Propagation R
Delay High to Low
e
L
Differential Propagation
Delay Low to High
Differential Skew
b
t
PHLD
t
PLHD
l
l
Rise Time 3 25 50 ns
Fall Time 3 25 50 ns
Disable Time High to Z C
e
L
Disable Time Low to Z RE *eL
Enable Time Z to High C
e
L
Enable Time Z to Low RE *eL
54X,C
15 pF
100 pF
e
100 pF
L
10 39 80 ns
10 40 80 ns
Figures 5, 6
0 1 10 ns
Figures 7, 8
Figures 9, 10
Figures 7, 8
Figures 9, 10
Ð 80 200 ns
Ð 80 200 ns
Ð 50 200 ns
Ð 65 200 ns
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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
RECEIVER CHARACTERISTICS
VTL.
A
ea
e
15 pF
L
Figures 12, 13
30 210 400 ns
30 190 400 ns
02050 ns
e
15 pF
L
Figures 14, 15, 16
Ð 50 150 ns
Ð 55 150 ns
Ð 45 150 ns
25§C.
and VOC, respectively, that occur when input changes state.
OD2
t
PHL
t
PLH
t
SK
t
PLZ
t
PHZ
t
PZL
t
PZH
Note 1: ‘‘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 2: Current into device pins is defined as positive. Current out of device pins is defined as negative. All voltages are referenced to ground except V
.
V
OD2
Note 3: All typicals are given for: V
Note 4: Delta
Note 5: Threshold parameter limits specified as an algebraic value rather than by magnitude.
Note 6: Hysteresis defined as V
Note 7: I
Note 8: C
Note 9: For complete details of test, see RS-485.
Propagation Delay C
High to Low
Propagation Delay
Low to High
PHL
b
t
l
PLH
Skew,lt
Output Disable Time C
Output Enable Time Ð 40 150 ns
ea
5.0V, T
V
and DeltalV
l
l
OD2
includes the receiver input current and driver TRI-STATE leakage current.
IN
includes probe and jig capacitance.
L
CC
are changes in magnitude of V
l
OC
e
b
V
HST
TH
Parameter Measurement Information
OD1
and
FIGURE 1. Driver V
OD2
and V
FIGURE 3. Driver VOHand V
TL/F/12040– 2
OC
TL/F/12040– 3
OL
FIGURE 5. Driver Differential Propagation Delay Test Circuit
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FIGURE 2. Driver V
Vtesteb7V toa12V
FIGURE 4. Driver I
TL/F/12040– 5
OSD
OD3
TL/F/12040– 18
TL/F/12040– 4
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Parameter Measurement Information (Continued)
FIGURE 6. Driver Differential Propagation Delays and Differential Rise and Fall Times
FIGURE 7. TRI-STATE Test Circuit (t
FIGURE 9. TRI-STATE Test Circuit (t
TL/F/12040– 7
PZH,tPHZ
TL/F/12040– 9
PZL,tPLZ
TL/F/12040– 6
FIGURE 8. TRI-STATE Waveforms (t
TL/F/12040– 8
PZH,tPHZ
)
)
FIGURE 10. TRI-STATE Waveforms (t
TL/F/12040– 10
PZL,tPLZ
)
)
FIGURE 11. Receiver VOHand V
TL/F/12040– 11
OL
FIGURE 12. Receiver Differential Propagation Delay
TL/F/12040– 12
Test Circuit
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Parameter Measurement Information (Continued)
FIGURE 13. Receiver Differential Propagation Delay Waveforms
TL/F/12040– 13
FIGURE 14. Receiver TRI-STATE Test Circuit
FIGURE 15. Receiver Enable and Disable Waveforms (t
PLZ,tPZL
TL/F/12040– 14
TL/F/12040– 15
)
FIGURE 16. Receiver Enable and Disable Waveforms (t
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PHZ,tPZH
)
TL/F/12040– 16
Page 7
Typical Application Information
FIGURE 17. Typical RS-485 Bus Interface
TL/F/12040– 17
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/RItDO*/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.
2RE*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.
7DO*/RI* Driver Output/Receiver Input, 485 Bus Pin.
8VCCPositive Power Supply Connection: Recommended operating range for VCCisa4.75V toa5.25V.
Unit Load
a
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
top border extending from
is defined as one unit load. Likewise, the bottom border
extending from
a
defined as one unit load (see
b
3Vat0mAtoa12V ata1mA
5Vat0mAtob7V atb0.8 mA is also
Figure 18
b
7V toa12V. The
). 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 applications, 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
(/2 unit load and (/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 (/2 UL option is available in industrial temperature and
the (/4 UL is available in commercial temperature.
First, for a (/2 UL device the top and bottom borders shown
in
Figure 18
and
a
12V ata0.5 mA for the top border andb7V atb0.4 mA
for the bottom border (see
device the top and bottom borders shown in
scaled also. Again, both 0 mA reference points at
b
3V stay the same. The other reference points area12V
are scaled. Both 0 mA reference points ata5V
b
3V stay the same. The other reference points are
Figure 18
). Second, for a (/4 UL
Figure 18
a
5V and
are
at
0.25 mA for the top border andb7V atb0.2 mA for
the bottom border (see
Figure 18
).
The advantage of the (/2 UL and (/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 automatic sleep mode function for power conscious applications. The DS36C280 has a slew rate control for EMI conscious 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.
FIGURE 18. Input Current vs Input Voltage
TL/F/12040– 19
Operating Range
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Page 8
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Physical Dimensions inches (millimeters)
8-Lead (0.150×Wide) Molded Small Outline Package, JEDEC
Order Number DS36C278TM, DS36C278M
NS Package Number M08A
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Page 10
Physical Dimensions inches (millimeters) (Continued)
8-Lead (0.300×Wide) Molded Dual-In-Line Package
Order Number DS36C278TN, DS36C278N
NS Package Number N08E
DS36C278 Low Power Multipoint EIA-RS-485 Transceiver
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. Life support devices or systems are devices or 2. A critical component is any component of a life
systems which, (a) are intended for surgical implant support device or system whose failure to perform can
into the body, or (b) support or sustain life, and whose be reasonably expected to cause the failure of the life
failure to perform, when properly used in accordance support device or system, or to affect its safety or
with instructions for use provided in the labeling, can effectiveness.
be reasonably expected to result in a significant injury
to the user.
National Semiconductor National Semiconductor National Semiconductor National Semiconductor
Corporation Europe Hong Kong Ltd. Japan Ltd.
1111 West Bardin Road Fax:
Arlington, TX 76017 Email: europe.support@nsc.com Ocean Centre, 5 Canton Rd. Fax: 81-043-299-2408
Tel: 1(800) 272-9959 Deutsch Tel:
Fax: 1(800) 737-7018 English Tel:
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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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Italiano Tel:a49 (0) 180-534 16 80 Fax: (852) 2736-9960
a
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