DS36C279
Low Power EIA-RS-485 Transceiver with Sleep Mode
General Description
The DS36C279 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 compat-
ible with TIA/EIA-422-B.
The sleep mode feature automatically puts the device in a
power saving mode when both the driver and receiver are
disabled.
The device is ideal for use in power conscious
applications where the device may be disabled for extended
periods of time.
The driver and receiver outputs feature TRI-STATE
capabil-
ity. The driver outputs operate over the entire common mode
range of -7V to +12V. 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 a high impedance state.
The receiver incorporates a fail safe circuit which guarantees
a high output state when the inputs are left open.
The DS36C279T is fully specified over the industrial tem-
perature range (-40C to +85C).
Features
n
100% RS-485 compliant
-- Guaranteed RS-485 device interoperation
n
Low power CMOS design:
I
CC
500 A max
n
Automatic sensing sleep mode
-- Reduces I
CC
to 10 A maximum
n
Built-in power up/down glitch-free circuitry
-- Permits live transceiver intersection/displacement
n
DIP and SOIC packages available
n
Industrial temperature range:
-40C to +85C
n
On-board thermal shutdown circuitry
-- Prevents damage to the device in the event of
excessive power dissipation
n
Wide common mode range:
-7V to +12V
n
Receive open input fail-safe (Note 1)
n
1
/
4
unit load (DS36C279):
128 nodes
n
1
/
2
unit load (DS36C279T):
64 nodes
n
ESD (Human Body Model):
2 kV
n
Drop-in replacement for:
-- LTC485 MAX485 DS75176 DS3695
Connection and Logic Diagram
Truth Table
DRIVER SECTION
RE*
DE
DI
DO/RI
DO*/RI*
X
H
H
H
L
X
H
L
L
H
X
L
X
Z
Z
RECEIVER SECTION
RE*
DE
RI-RI*
RO
L
L
+0.2V
H
L
L
-0.2V
L
H
L
X
Z (Note 2)
L
L
OPEN (Note 1)
H
Note 1: Non-terminated, open input only
Note 2: Device enters sleep mode if enable conditions are held 600 ns
TRI-STATE
is a registered trademark of National Semiconductor Corporation.
DS012053-1
Order Number DS36C279M, DS36C279N,
DS36C279TM or DS36C279TN
See NS Package Number M08A or N08E
July 1998
DS36C279
Low
Power
EIA-RS-485
T
ransceiver
with
Sleep
Mode
1999 National Semiconductor Corporation
DS012053
www.national.com
Absolute Maximum Ratings
(Note 3)
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
@
+25C
M Package 1190 mW, derate
9.5 mW/C above +25C
N Package 744 mW, derate
6.0 mW/C above +25C
Storage Temperature Range
-65C to +150C
Lead Temperature
(Soldering 4 sec)
+260C
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 (T
A
)
DS36C279T
-40
+25
+85
C
DS36C279
0
+25
+70
C
Electrical Characteristics
(Notes 4, 5)
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
= 50
(422)
Figure 1
2.0
2.8
V
(Termination Load)
R
L
= 27
(485)
1.5
2.3
5.0
V
V
OD2
Balance of V
OD2
R
L
= 27
or 50
(Note 6)
-0.2
0.1
+0.2
V
|V
OD2
- V
OD2*
|
(422, 485)
V
OD3
Differential Output Voltage
R1 = 54
, R2 = 375
Figure 2
1.5
2.0
5.0
V
(Full Load)
V
TEST
= -7V to +12V
V
OC
Driver Common Mode
R
L
= 27
(485)
Figure 1
0
3.0
V
Output Voltage
R
L
= 50
(422)
0
3.0
V
V
OC
Balance of V
OC
R
L
= 27
or
(Note 6)
-0.2
+0.2
V
|V
OC
- V
OC*
|
R
L
= 50
(422, 485)
I
OSD
Driver Output Short-Circuit
V
O
= +12V
(485)
Figure 4
200
+250
mA
Current
V
O
= -7V
(485)
-190
-250
mA
RECEIVER CHARACTERISTICS
V
TH
Differential Input High
Threshold Voltage
V
O
= V
OH
, I
O
= -0.4 mA
(Note 7)
(422, 485)
+0.035
+0.2
V
-7V
V
CM
+12V
V
TL
Differential Input Low
Threshold Voltage
V
O
= V
OL
, I
O
= 0.4 mA
-0.2
-0.035
V
-7V
V
CM
+12V
V
HST
Hysteresis
V
CM
= 0V
(Note 8)
70
mV
R
IN
Input Resistance
-7V
V
CM
+12V
DS36C279T
24
68
k
DS36C279
48
68
k
I
IN
Line Input Current
Other Input = 0V,
DS36C279
V
IN
= +12V
0
0.19
0.25
mA
(Note 9)
DE = V
IL
, RE* = V
IL
,
V
IN
= -7V
0
-0.1
-0.2
mA
V
CC
= 4.75 to 5.25
DS36C279T
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,
DE = V
IL
, RE* = V
IL
,
DS36C279
V
IN
= +12V
0
0.19
0.25
mA
(Note 9)
V
IN
= -7V
0
-0.1
-0.2
mA
V
CC
= +3.0V or 0V,
T
A
= 25C
DS36C279T
V
IN
= +12V
0
0.19
0.5
mA
V
IN
= -7V
0
-0.1
-0.4
mA
I
B
Input Balance Test
RS = 500
(422) (Note 12)
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
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2
Electrical Characteristics
(Notes 4, 5) (Continued)
Over Supply Voltage and Operating Temperature ranges, unless otherwise specified
Symbol
Parameter
Conditions
Reference
Min
Typ
Max
Units
RECEIVER CHARACTERISTICS
I
OSR
Short Circuit Current
V
O
= GND
RO
7
35
85
mA
I
OZR
TRI-STATE Leakage
Current
V
O
= 0.4V to 2.4V
1
A
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
2
A
I
IL
Low Level Input Current
V
CC
= 5V
V
IL
= 0V
-2
A
V
CC
= +3.0V
-2
A
I
CC
Power Supply Current
(No Load)
Driver and Receiver ON
V
CC
200
500
A
I
CCR
Driver OFF, Receiver ON
200
500
A
I
CCD
Driver ON, Receiver OFF
200
500
A
I
CCX
Sleep Mode
0.2
10
A
Switching Characteristics
(Notes 5, 10)
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
= 54
, 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
0
1
10
ns
|t
PHLD
- t
PLHD
|
t
r
Rise Time
3
25
50
ns
t
f
Fall Time
3
25
50
ns
t
PHZ
Disable Time High to Z
C
L
= 15 pF
RE* = L
Figures 7, 8
80
200
ns
t
PLZ
Disable Time Low to Z
Figures 9, 10
80
200
ns
t
PZH
Enable Time Z to High
C
L
= 100 pF
RE* = L
Figures 7, 8
50
200
ns
t
PZL
Enable Time Z to Low
Figures 9, 10
65
200
ns
t
PSH
Driver Enable from Sleep
C
L
= 100 pF
Figures 7, 8
70
98
250
ns
Mode to Output High
(Note 11)
t
PSL
Driver Enble from Sleep
C
L
= 100 pF
Figures 9, 10
70
98
250
ns
Mode to Output Low
(Note 11)
RECEIVER CHARACTERISTICS
t
PHL
Propagation Delay
C
L
= 15 pF
Figures 12, 13
30
210
400
ns
High to Low
t
PLH
Propagation Delay
30
190
400
ns
Low to High
t
SK
Skew, |t
PHL
- t
PLH
|
0
20
50
ns
t
PLZ
Output Disable Time
C
L
= 15 pF
Figures 14, 15,
16
50
150
ns
t
PHZ
DE = H
55
150
ns
t
PZL
Output Enable Time
40
150
ns
t
PZH
45
150
ns
t
PSH
Receiver Enable from Sleep
C
L
= 15 pF
Figures 14, 16
70
97
250
ns
Mode to Output High
(Note 11)
t
PSL
Receiver Enable from Sleep
C
L
= 15 pF
Figures 14, 15
70
95
250
ns
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3
Switching Characteristics
(Notes 5, 10) (Continued)
Over Supply Voltage and Operating Temperature ranges, unless otherwise specified
Symbol
Parameter
Conditions
Reference
Min
Typ
Max
Units
RECEIVER CHARACTERISTICS
Mode to Output Low
(Note 11)
Note 3: "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 4: 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
OD1
and V
OD2
.
Note 5: All typicals are given for: V
CC
= +5.0V, T
A
= + 25C.
Note 6: Delta |V
OD2
| and Delta |V
OC
| are changes in magnitude of V
OD2
and V
OC
, respectively, that occur when input changes state.
Note 7: Threshold parameter limits specified as an algebraic value rather than by magnitude.
Note 8: Hysteresis defined as V
HST
= V
TH
- V
TL
.
Note 9: I
IN
includes the receiver input current and driver TRI-STATE leakage current.
Note 10: C
L
includes probe and jig capacitance.
Note 11: For enable from sleep mode delays DE = L and RE* = H for greater than 600 ns prior to test (device is in sleep mode).
Note 12: For complete details of test, see RS-485.
Parameter Measurement Information
DS012053-2
FIGURE 1. Driver V
OD2
and V
OC
DS012053-17
FIGURE 2. Driver V
OD3
DS012053-3
FIGURE 3. Driver V
OH
and V
OL
DS012053-4
Vtest = -7V to +12V
FIGURE 4. Driver I
OSD
DS012053-5
FIGURE 5. Driver Differential Propagation Delay Test Circuit
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4
Parameter Measurement Information
(Continued)
DS012053-6
FIGURE 6. Driver Differential Propagation Delays and Differential Rise and Fall Times
DS012053-7
FIGURE 7. TRI-STATE and Sleep Mode Test Circuit
(t
PZH
, (t
PSH
), t
PHZ
)
DS012053-8
FIGURE 8. TRI-STATE and Sleep Mode Waveforms
(t
PZH
, (t
PSH
), t
PHZ
)
DS012053-9
FIGURE 9. TRI-STATE and Sleep Mode Test Circuit
(t
PZL
, (t
PSL
), t
PLZ
)
DS012053-10
FIGURE 10. TRI-STATE and Sleep Mode Waveforms
(t
PZL
, (t
PSL
), t
PLZ
)
DS012053-11
FIGURE 11. Receiver V
OH
and V
OL
DS012053-12
FIGURE 12. Receiver Differential Propagation Delay
Test Circuit
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5
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