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 A of supply current when un-
loaded or 0.2 A when in the automatic sleep mode. Sleep
mode is activated by inactivity on the enables (DE and RE
(Note 1)). Holding DE =L and 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 tempera-
ture range operation.
Features
n
Meets TIA/EIA RS-485 multipoint standard
n
Sleep mode reduces I
CC
to 0.2 A
n
Guaranteed full load output voltage (V
OD3
)
n
Low quiescent current:
200 A 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
0C to +70C
DIP/N08E
DS481M
0C to +70C
SOP/M08A
DS481TN
-40C to +85C
DIP/N08E
DS481TM
-40C to +85C
SOP/M08A
Truth Table
DRIVER SECTION
RE
(Note 1)
DE
DI
A
B
X
H
H
H
L
X
H
L
L
H
X
L
X
Z
Z (Note 2)
RECEIVER SECTION
RE
(Note 1)
DE
A-B
RO
L
L
+0.2V
H
L
L
-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
T
ransceiver
with
Sleep
Mode
1999 National Semiconductor Corporation
DS012919
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
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
@
+25C
M Package
1.19W
N Package
0.74W
Derate M Package 9.5 mW/C above +25C
Derate N Package 6.0 mW/C above +25C
Maximum Package Power Dissipation
@
+70C
M Package
0.76W
N Package
0.47W
Storage Temperature Range
-65C to +150C
Lead Temperature Range
(Soldering, 4 sec.)
+260C
ESD (HBM)
2 kV
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
= 50
, (RS422),
Figure 1
2
2.8
V
with Load
R
L
= 27
, (RS485),
Figure 1
1.5
2.3
5
V
V
OD
Change in Magnitude of Output
R
L
= 27
or 50
(Note 6)
0.2
|V|
Differential Voltage
V
OD3
Differential Driver Output Voltage --
R1 = 54
, R2 = 375
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
= 27
or 50
,
Figure 1
0
3
V
V
OC
Change in Magnitude of Common-Mode
R
L
= 27
or 50
,
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
2
A
I
IN2
Input Current (Note 7)
DE = 0V, V
CC
= 0V or 5.25V
V
IN
= +12V
DS481
A, B
0
190
250
A
V
IN
= -7V
0
-100 -200
A
V
IN
= +12V
DS481T
0
190
500
A
V
IN
= -7V
0
-100 -400
A
V
TH
Receiver Differential Threshold Voltage
-7V
V
CM
+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
V
O
2.4V
1
A
R
IN
Receiver Input Resistance
-7V
V
IN
+12V
DS481
A, B
48
68
k
DS481T
24
I
CC
No-Load Supply Current (Note 8)
DE = V
CC
, RE (Note 1) = 0V or V
CC
V
CC
200
500
A
DE = 0V, RE (Note 1) = 0V or V
CC
200
500
A
I
CCX
Sleep Mode Supply Current
DE = GND
V
CC
0.2
10
A
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
www.national.com
2
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
= 54
, 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
- t
PLHD
|
0
1
10
ns
t
r
Driver Rise Time
3
25
50
ns
t
f
Driver Fall Time
3
25
50
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
- t
PLHD
|
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
= +25C.
Note 6:
|V
OD
| and
|V
OC
| are changes in magnitude of V
OD
and V
OC
respectively, 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 t
f
6 ns, Z
O
= 50
.
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 (t
r
) 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).
www.national.com
3
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.
www.national.com
4
Parameter Measurement Information
(Continued)
DS012919-11
FIGURE 10.
DS012919-12
FIGURE 11.
DS012919-13
FIGURE 12.
DS012919-14
FIGURE 13.
www.national.com
5
PDF 
ZIP