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DS36C279
Low Power EIA-RS-485 Transceiver with Sleep Mode
General Description
The DS36C279 is a low power differential bus/line transceiver designed to meet the requirements of RS-485 Standard formultipoint data transmission. In addition it is compatible 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
®
capability.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 temperature range (−40˚C to +85˚C).
Features
n 100%RS-485 compliant
— Guaranteed RS-485 device interoperation
n Low power CMOS design: I
CC
500 µA max
n Automatic sensing sleep mode
— Reduces I
CC
to 10 µA 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: −40˚C to +85˚C
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
⁄4unit load (DS36C279): ≥ 128 nodes
n
1
⁄2unit load (DS36C279T): ≥ 64 nodes
n ESD (Human Body Model): ≥ 2kV
n Drop-in replacement for:
— LTC485 MAX485 DS75176 DS3695
Connection and Logic Diagram 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
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 Transceiver with Sleep Mode
© 1999 National Semiconductor Corporation DS012053 www.national.com
Page 2
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
@
+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 (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 IO= 0 mA (No Load) (422)
(485)
1.5 5.0 V
V
OD0
Output Voltage IO= 0 mA 0 5.0 V
V
OD0*
Output Voltage (Output to GND) 0 5.0 V
V
OD2
Differential Output Voltage RL=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
RL=27Ωor 50Ω (Note 6) −0.2 0.1 +0.2 V
|V
OD2−VOD2*
| (422, 485)
V
OD3
Differential Output Voltage R1 = 54Ω,R2=375Ω
Figure 2
1.5 2.0 5.0 V
(Full Load) V
TEST
= −7V to +12V
V
OC
Driver Common Mode RL=27Ω (485)
Figure 1
0 3.0 V
Output Voltage R
L
=50Ω (422) 0 3.0 V
∆V
OC
Balance of V
OC
RL=27Ωor (Note 6) −0.2 +0.2 V
|V
OC−VOC*
|R
L
=50Ω (422, 485)
I
OSD
Driver Output Short-Circuit VO= +12V (485)
Figure 4
200 +250 mA
Current V
O
= −7V (485) −190 −250 mA
RECEIVER CHARACTERISTICS
V
TH
Differential Input High
Threshold Voltage
VO=VOH,IO= −0.4 mA
(Note 7)
(422, 485)
+0.035 +0.2 V
−7V ≤ V
CM
≤ +12V
V
TL
Differential Input Low
Threshold Voltage
VO=VOL,IO= 0.4 mA −0.2 −0.035 V
−7V ≤ V
CM
≤ +12V
V
HST
Hysteresis VCM= 0V (Note 8) 70 mV
R
IN
Input Resistance −7V ≤ VCM≤ +12V DS36C279T 24 68 kΩ
DS36C279 48 68 kΩ
I
IN
Line Input Current Other Input = 0V, DS36C279 VIN= +12V 0 0.19 0.25 mA
(Note 9) DE = V
IL
,RE*=VIL,V
IN
= −7V 0 −0.1 −0.2 mA
V
CC
= 4.75 to 5.25 DS36C279T VIN= +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*=VIL,
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
= 25˚C
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 = 500Ω (422) (Note 12)
±
400 mV
V
OH
High Level Output Voltage IOH= −4 mA, VID= +0.2V RO
Figure 11
3.5 4.6 V
V
OL
Low Level Output Voltage IOL= +4 mA, VID= −0.2V 0.3 0.5 V
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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 VO= GND RO 7 35 85 mA
I
OZR
TRI-STATE Leakage
Current
VO= 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 VIH=V
CC
2µA
I
IL
Low Level Input Current VCC=5V VIL=0V −2 µA
V
CC
= +3.0V −2 µA
I
CC
Power Supply Current
(No Load)
Driver and Receiver ON
V
CC
200 500 µA
I
CCR
Driver OFF, Receiver ON 200 500 µA
I
CCD
Driver ON, Receiver OFF 200 500 µA
I
CCX
Sleep Mode 0.2 10 µA
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
RL=54Ω,CL= 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−tPLHD
|
t
r
Rise Time 32550 ns
t
f
Fall Time 32550 ns
t
PHZ
Disable Time High to Z CL=15pF
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 CL= 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 CL= 100 pF
Figures 7, 8
70 98 250 ns
Mode to Output High (Note 11)
t
PSL
Driver Enble from Sleep CL= 100 pF
Figures 9, 10
70 98 250 ns
Mode to Output Low (Note 11)
RECEIVER CHARACTERISTICS
t
PHL
Propagation Delay CL=15pF
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−tPLH
| 0 20 50 ns
t
PLZ
Output Disable Time CL=15pF
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 CL=15pF
Figures 14, 16
70 97 250 ns
Mode to Output High (Note 11)
t
PSL
Receiver Enable from Sleep CL=15pF
Figures 14, 15
70 95 250 ns
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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 pinsis defined as positive. Current out of device pins is defined as negative.Allvoltagesarereferencedto ground except V
OD1
and V
OD2
.
Note 5: All typicals are given for: V
CC
= +5.0V, TA= + 25˚C.
Note 6: Delta |V
OD2
| and Delta |VOC| are changes in magnitude of V
OD2
and VOC, 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=VTH−VTL
.
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 VOHand 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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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 VOHand V
OL
DS012053-12
FIGURE 12. Receiver Differential Propagation Delay
Test Circuit
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Parameter Measurement Information (Continued)
DS012053-13
FIGURE 13. Receiver Differential Propagation Delay Waveforms
DS012053-14
FIGURE 14. Receiver TRI-STATE and Sleep Mode Test Circuit
DS012053-15
FIGURE 15. Receiver Enable and Disable Waveforms (t
PLZ,tPZL
,(t
PSL
))
DS012053-16
FIGURE 16. Receiver Enable and Disable Waveforms (t
PHZ,tPZH
,(t
PSH
))
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Parameter Measurement Information (Continued)
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). When RE* is HIGH and DE is LOW, the device will enter a
low-current sleep mode after 600 ns.
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). When RE* is HIGH and DE is LOW, the device will enter a
low-current sleep mode after 600 ns.
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 VCCis +4.75V to +5.25V.
Unit Load
Aunit 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 extending
from +5V at 0 mA to −7V at −0.8 mA is also defined as one
unit load (see
Figure 19
). 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
DS012053-19
FIGURE 17. Entering Sleep Mode Conditions
DS012053-18
FIGURE 18. Typical RS-485 Bus Interface
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Unit Load (Continued)
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
⁄2unit load and1⁄4unit 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
⁄2UL option is available in industrial temperature and
the
1
⁄4UL is available in commercial temperature.
First, for a
1
⁄2UL device the top and bottom borders shown in
Figure 19
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 19
). Second, for a1⁄4UL device the
top and bottom borders shown in
Figure 19
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 19
).
The advantage of the
1
⁄2UL and1⁄4UL 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.
Sleep Mode
The DS36C279 features an automatic shutdown mode that
allows the device to save power when not transmitting data.
Since the shutdown mode is automatic, no external components are required. It may be used as little or as much as the
application requires. The more the feature is utilized, the
more power it saves.
The sleep mode is automatically entered when both the
driver and receiver are disabled. This occurs when both the
DE pin is asserted to a logic low and the RE* pin is asserted
to a logic high. Once both pins are asserted the device will
enter sleep mode typically in 50 ns. The DS36C279 is guaranteed to go into sleep mode within 600 ns after both pins
are asserted. The device wakes up (comes out of sleep
mode) when either the DE pin is asserted to a logic high
and/or the RE* pin is asserted to a logic low. After the device
enters sleep mode it will take longer for the device to wake
up than it does for the device to enable from TRI-STATE.Refer to datasheet specifications t
PSL
and t
PSH
and compare
with t
PZL
and t
PZH
for timing differences.
The benefit of the DS36C279 is definitely its power savings.
When active the device has a maximum I
CC
of 500 µA.
When in sleep mode the device has a maximum I
CC
of only
10 µA, which is 50 times less power than when active. The
I
CC
when the device is active is already very low but when in
sleep mode the I
CC
is ultra low.
DS012053-20
FIGURE 19. Input Current vs Input Voltage
Operating Range
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Physical Dimensions inches (millimeters) unless otherwise noted
8-Lead (0.150" Wide) Molded Small Outline Package, JEDEC
Order Number DS36C279M or DS36C279TM
NS Package Number M08A
8-Lead (0.300" Wide) Molded Dual-In-Line Package
Order Number DS36C279N or DS36C279TN
NS Package Number N08E
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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 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.
National Semiconductor
Corporation
Americas
Tel: 1-800-272-9959
Fax: 1-800-737-7018
Email: support@nsc.com
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DS36C279 Low Power EIA-RS-485 Transceiver with Sleep Mode
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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