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DS481
Low Power RS-485/RS-422 Multipoint Transceiver with
Sleep Mode
General Description
The DS481 is a low-power transceiver for RS-485 and
RS-422 communication. The device contains one driver and
one receiver.The drivers slew rate allows for operation up to
2.0 Mbps (see Applications Information section).
The transceiver draws 200 µA of supply current when un-
loaded or 0.2 µA when in the automatic sleep mode. Sleep
mode is activated by inactivity on the enables (DE and RE
(Note 1)). Holding DE=Land RE(Note 1)=H for greater than
600 ns will enable the sleep mode. The DS481 operates
from a single +5V supply.
The driver is short-circuit current limited and is protected
against excessive power dissipation by thermal shutdown
circuitry that places the driver outputs into TRI-STATE
®
(High Impedance state) under fault conditions. The driver
guarantees a minimum of 1.5V differential output voltage
with maximum loading across the common mode range
(V
OD3
).
The receiver has a failsafe feature that guarantees a
logic-high output if the input is open circuit.
The DS481 is available in surface mount and DIP packages
and is characterized for Industrial and Commercial temperature range operation.
Features
n Meets TIA/EIA RS-485 multipoint standard
n Sleep mode reduces I
CC
to 0.2 µA
n Guaranteed full load output voltage (V
OD3
)
n Low quiescent current: 200 µA typ
n −7V to +12V common-mode input voltage range
n TRI-STATE outputs on driver and receiver
n AC performance:
— Driver transition time: 25 ns typ
— Driver propagation delay: 40 ns typ
— Driver skew: 1 ns typ
— Receiver propagation delay: 200 ns typ
— Receiver skew: 20 ns typ
n Half-duplex flow through pinout
n Operates from a single 5V supply
n Allows up to 128 transceivers on the bus (DS481N/M)
n Allows up to 64 tranceivers on the bus (DS481TN/M)
n Current-limiting and thermal shutdown for driver
overload protection
n Industrial temperature range operation
n Pin and functional compatible with MAX481C and
MAX481E
Connection and Logic Diagram
Order Number Temp. Range Package/
###
DS481N 0˚C to +70˚C DIP/N08E
DS481M 0˚C to +70˚C SOP/M08A
DS481TN −40˚C to +85˚C DIP/N08E
DS481TM −40˚C to +85˚C SOP/M08A
Truth Table
DRIVER SECTION
RE
(Note 1)
DE DI A B
XHHH L
XHLL H
X L X Z Z (Note 2)
RECEIVER SECTION
RE
(Note 1)
DE A-B RO
LL ≥+0.2V H
LL ≤−0.2V L
H X X Z (Note 2)
L L OPEN (Note 1) H
X=indeterminate
Z=TRI-STATE
Note 1: Non Terminated, Open Input only
Note 2: Device enters sleep mode if enable conditions are held
>
600 ns,
DE=L and RE (Note 1)=H.
TRI-STATE®is a registered trademark of National Semiconductor Corporation.
DS012919-1
*Note: Non Terminated, Open Input only
July 1998
DS481 Low Power RS-485/RS-422 Multipoint Transceiver with Sleep Mode
© 1999 National Semiconductor Corporation DS012919 www.national.com
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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
Enable Input Voltage
(RE (Note 1), DE) −0.5V to (V
CC
+ 0.5V)
Driver Input Voltage (DI) −0.5V to (V
CC
+ 0.5V)
Driver Output Voltage (A, B) −14V to +14V
Receiver Input Voltage (A, B) −14V to +14V
Receiver Output Voltage (RO) −0.5V to (V
CC
+ 0.5V)
Maximum Package Power Dissipation
@
+25˚C
M Package 1.19W
N Package 0.74W
Derate M Package 9.5 mW/˚C above +25˚C
Derate N Package 6.0 mW/˚C above +25˚C
Maximum Package Power Dissipation
@
+70˚C
M Package 0.76W
N Package 0.47W
Storage Temperature Range −65˚C to +150˚C
Lead Temperature Range
(Soldering, 4 sec.) +260˚C
ESD (HBM) ≥2kV
Recommended Operating
Conditions
Min Typ Max Units
Supply Voltage (V
CC
) +4.75 +5.0 +5.25 V
Operating Free Air
Temperature (T
A
)
DS481 0 +25 +70 ˚C
DS481T −40 +25 +85 ˚C
Bus Common Mode Voltage −7 +12 V
Electrical Characteristics
Over Supply Voltage and Operating Temperature Ranges, unless otherwise specified (Notes 4, 5)
Symbol Parameter Conditions Pin Min Typ Max Units
V
OD1
Differential Driver Output Voltage (No Load) A, B 1.5 5 V
V
OD2
Differential Driver Output Voltage R
L
=
50Ω, (RS422),
Figure 1
2 2.8 V
with Load R
L
=
27Ω, (RS485),
Figure 1
1.5 2.3 5 V
∆V
OD
Change in Magnitude of Output R
L
=
27Ω or 50Ω (Note 6) 0.2 |V|
Differential Voltage
V
OD3
Differential Driver Output Voltage— R1=54Ω,R2=375Ω 1.5 2.0 5 V
Full Load with Max V
CM
V
TEST
=
−7V to +12V,
Figure 2
V
OC
Driver Common-Mode Output Voltage R
L
=
27Ω or 50Ω,
Figure 1
03V
∆V
OC
Change in Magnitude of Common-Mode R
L
=
27Ω or 50Ω,
Figure 1
0.2 |V|
Output Voltage (Note 6)
V
IH
Input High Voltage DI, DE, RE
(Note 1)
2.0 V
V
IL
Input Low Voltage 0.8 V
I
IN1
Input Current V
IN
=
0V or V
CC
±
2µA
I
IN2
Input Current (Note 7)
DE=0V, V
CC
=
0V or 5.25V
V
IN
=
+12V DS481 A, B 0 190 250 µA
V
IN
=
−7V 0 −100 −200 µA
V
IN
=
+12V DS481T 0 190 500 µA
V
IN
=
−7V 0 −100 −400 µA
V
TH
Receiver Differential Threshold Voltage −7V ≤ VCM≤ +12V −0.2 0.2 V
∆V
TH
Receiver Input Hysteresis V
CM
=
0V 70 mV
V
OH
Receiver Output High Voltage I
O
=
−4 mA, V
ID
=
0.2V RO 3.5 V
V
OL
Receiver Output Low Voltage I
O
=
4 mA, V
ID
=
−0.2V 0.5 V
I
OZR
TRI-STATE Output Current at Receiver 0.4V ≤ VO≤ 2.4V
±
1µA
R
IN
Receiver Input Resistance −7V ≤ VIN≤ +12V DS481 A, B 48 68 kΩ
DS481T 24
I
CC
No-Load Supply Current (Note 8) DE=VCC, RE (Note 1)=0V or V
CC
V
CC
200 500 µA
DE=0V, RE (Note 1)=0V or V
CC
200 500 µA
I
CCX
Sleep Mode Supply Current DE=GND V
CC
0.2 10 µA
RE (Note 1)=V
CC
(Figure 14)
I
OSD1
Driver Short Circuit Current, V
O
=
HIGH −7V ≤ V
O
≤ +12V A, B 250 mA
I
OSD2
Driver Short Circuit Current, V
O
=
LOW −7V ≤ V
O
≤ +12V −250 mA
I
OSR
Receiver Short Circuit Current V
O
=
GND RO 7 85 mA
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Switching Characteristics
Over Supply Voltage and Operating Temperature Ranges, unless otherwise specified (Notes 5, 9, 10)
Symbol Parameter Conditions Min Typ Max Units
t
PLHD
Driver Differential Propagation Delay— Low to High R
L
=
54Ω,C
L
=
100 pF 10 40 80 ns
t
PHLD
Driver Differential Propagation Delay— High to Low 10 39 80 ns
t
SKEW
Differential Skew |t
PHLD−tPLHD
|0110ns
t
r
Driver Rise Time 32550 ns
t
f
Driver Fall Time 32550 ns
t
ZH
Driver Enable to Output High C
L
=
100 pF 50 200 ns
t
ZL
Driver Enable to Output Low C
L
=
100 pF 65 200 ns
t
LZ
Driver Disable from Output Low C
L
=
15 pF 80 200 ns
t
HZ
Driver Disable from Output High C
L
=
15 pF 80 200 ns
t
PSH
Driver Enable from Sleep C
L
=
100 pF 70 98 250 ns
Mode to Output High (Note 12)
(Figures 5, 6)
t
PSL
Driver Enable from Sleep C
L
=
100 pF 70 98 250 ns
Mode to Output Low (Note 12)
(Figures 7, 8)
t
PLHD
Receiver Differential Propagation Delay— Low to High C
L
=
15 pF (RO) 30 190 400 ns
t
PHLD
Receiver Differential Propagation Delay— High to Low 30 210 400 ns
t
SKEW
Differential Skew |t
PHLD−tPLHD
| 0 20 50 ns
t
ZH
Receiver Enable to Output High C
L
=
15 pF 45 150 ns
t
ZL
Receiver Enable to Output Low 40 150 ns
t
LZ
Receiver Disable from Output Low 50 150 ns
t
HZ
Receiver Disable from Output High 55 150 ns
t
PSH
Receiver Enable from Sleep C
L
=
15 pF 70 97 250 ns
Mode to Output High (Note 12)
(Figures 11, 13)
t
PSL
Receiver Enable from Sleep C
L
=
15 pF 70 95 250 ns
Mode to Output Low (Note 12)
(Figures 11, 12)
t
SLEEP
Time to Sleep (Device) DE=L and RE (Note 1)=H 50 600 ns
(Figure 14)
f
max
Maximum Data Rate (Note 11) 2.0 Mbps
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
OD1/2/3
and
V
ID
.
Note 5: All typicals are given for: V
CC
=
+5.0V, T
A
=
+25˚C.
Note 6: ∆|V
OD
| and ∆|VOC| are changes in magnitude of VODand VOCrespectively, that occur when the input changes state.
Note 7: I
IN2
includes the receiver input current and driver TRI-STATE leakage current.
Note 8: Supply current specification is valid for loaded transmitters when DE=0V or enabled (DE=H) with no load.
Note 9: f=1 MHz, t
r
and tf≤ 6 ns, Z
O
=
50Ω.
Note 10: C
L
includes jig and probe capacitance.
Note 11: f
max
is the guaranteed data rate for 50 ft of twisted pair cable. f
max
may be conservatively determined from the ratio of driver transition time (tr) to the data
rate unit interval (1/f
max
). Using a 10%ratio yields f
max
=
(0.1)/50 ns=2.0 Mb/s. Higher data rates may be supported by allowing larger ratios.
Note 12: For enable from sleep mode delays DE=L and RE (Note 1)=H for greater than 600 ns prior to test (device is in sleep mode).
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Parameter Measurement Information
DS012919-2
FIGURE 1. V
OD
DS012919-3
FIGURE 2. V
OD3
DS012919-4
FIGURE 3.
DS012919-5
FIGURE 4.
DS012919-6
FIGURE 5.
DS012919-7
FIGURE 6.
DS012919-8
FIGURE 7.
DS012919-9
FIGURE 8.
DS012919-10
FIGURE 9.
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Parameter Measurement Information (Continued)
DS012919-11
FIGURE 10.
DS012919-12
FIGURE 11.
DS012919-13
FIGURE 12.
DS012919-14
FIGURE 13.
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Parameter Measurement Information (Continued)
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
(Note 1)/RI (Note 1) by 200 mV, RO will be HIGH. If DO/RI ≤ DO (Note 1)/RI (Note 1) by 200 mV,
RO will be LOW. Additionally RO will be HIGH for OPEN (Non-terminated) Inputs.
2RE
(Note 1)
Receiver Output Enable: When RE (Note 1) is LOW the receiver output is enabled. When RE (Note
1) is HIGH, the receiver output is in TRI-STATE (OFF). When RE (Note 1) 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 (Note 1) 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 (Note 1)/RI (Note 1) will be HIGH. If DI is HIGH, then DO/RI is HIGH and DO
(Note 1)/RI (Note 1) is LOW.
5 GND Ground Connection.
6 DO/RI Driver Output/Receiver Input, 485 Bus Pin.
7DO
(Note 1)
/RI
(Note 1)
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 15
). 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.
The DS481 has
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 tem-
perature.
First, for a
1
⁄2UL device the top and bottom borders shown in
Figure 15
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 15
). Second, for a1⁄4UL device the
top and bottom borders shown in
Figure 15
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 15
).
The advantage of the
1
⁄2UL and1⁄4UL devices is the in-
creased number of nodes on one bus. In a single master
DS012919-15
*Note: Non Terminated, Open Input only
FIGURE 14. Entering Sleep Mode Conditions (modes and exit parameters shown)
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Unit Load (Continued)
multi-slave type of application where the number of slaves
exceeds 32, the DS481 may save in thecost of extra devices
like repeaters, extra media like cable, and/or extra components like resistors.
Sleep Mode
The DS481 features an automatic sleep mode that allows
the device to save power when not transmitting data. Since
the sleep 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 (Note 1) pin is
asserted to a logic high. Once both pins are asserted the device will enter sleep mode after 50 ns. The DS481 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 (Note 1) 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 DS481 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.
Applications Information (Continued)
DS012919-16
FIGURE 15. Input Current vs Input Voltage
Operating Range
Multipoint RS-485 Application
DS012919-17
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8
Page 9
Physical Dimensions inches (millimeters) unless otherwise noted
Order Number DS481M or DS481TM
NS Package Number M08A
Order Number DS481N or DS481TN
NS Package Number N08E
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with instructions for use provided in the labeling, can
be reasonably expected to result in a significant injury
to the user.
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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.
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DS481 Low Power RS-485/RS-422 Multipoint 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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