NSC DS481TN

DS481
Low Power RS-485/RS-422 Multipoint Transceiver with
Sleep Mode
General Description
Features
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 unloaded 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 = 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
(VOD3).
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.
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Connection and Logic Diagram
Truth Table
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Meets TIA/EIA RS-485 multipoint standard
Sleep mode reduces ICC to 0.2 µA
Guaranteed full load output voltage (V OD3)
Low quiescent current: 200 µA typ
−7V to +12V common-mode input voltage range
TRI-STATE outputs on driver and receiver
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
Half-duplex flow through pinout
Operates from a single 5V supply
Allows up to 128 transceivers on the bus (DS481N/M)
Allows up to 64 tranceivers on the bus (DS481TN/M)
Current-limiting and thermal shutdown for driver
overload protection
Industrial temperature range operation
Pin and functional compatible with MAX481C and
MAX481E
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
DS012919-1
*Note: Non Terminated, Open Input only
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
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.
© 1999 National Semiconductor Corporation
DS012919
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DS481 Low Power RS-485/RS-422 Multipoint Transceiver with Sleep Mode
July 1998
Absolute Maximum Ratings (Note 3)
M Package
N Package
Storage Temperature Range
Lead Temperature Range
(Soldering, 4 sec.)
ESD (HBM)
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
Supply Voltage (VCC)
+12V
Enable Input Voltage
(RE (Note 1), DE)
−0.5V to (VCC + 0.5V)
Driver Input Voltage (DI)
−0.5V to (VCC + 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 (VCC + 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
0.76W
0.47W
−65˚C to +150˚C
+260˚C
≥2 kV
Recommended Operating
Conditions
Supply Voltage (VCC)
Operating Free Air
Temperature (TA)
DS481
DS481T
Bus Common Mode Voltage
Min
+4.75
Typ
+5.0
Max
+5.25
Units
V
0
−40
−7
+25
+25
+70
+85
+12
˚C
˚C
V
Electrical Characteristics
Over Supply Voltage and Operating Temperature Ranges, unless otherwise specified (Notes 4, 5)
Symbol
Parameter
VOD1
Differential Driver Output Voltage
VOD2
Differential Driver Output Voltage
with Load
∆VOD
Change in Magnitude of Output
Conditions
(No Load)
RL = 50Ω, (RS422), Figure 1
RL = 27Ω, (RS485), Figure 1
RL = 27Ω or 50Ω (Note 6)
Pin
Min Typ Max Units
A, B
1.5
5
2
2.8
1.5
2.3
V
V
5
V
0.2
|V|
5
V
Differential Voltage
VOC
Driver Common-Mode Output Voltage
∆VOC
Change in Magnitude of Common-Mode
R1 = 54Ω, R2 = 375Ω
VTEST = −7V to +12V, Figure 2
RL = 27Ω or 50Ω, Figure 1
RL = 27Ω or 50Ω, Figure 1
Output Voltage
(Note 6)
VOD3
Differential Driver Output Voltage —
Full Load with Max VCM
VIH
Input High Voltage
VIL
Input Low Voltage
IIN1
Input Current
IIN2
Input Current (Note 7)
DE = 0V, VCC = 0V or 5.25V
VIN = 0V or VCC
VIN = +12V
VIN = −7V
Receiver Differential Threshold Voltage
∆VTH
Receiver Input Hysteresis
DS481
A, B
DS481T
VOH
Receiver Output High Voltage
Receiver Output Low Voltage
IO = −4 mA, VID = 0.2V
IO = 4 mA, VID = −0.2V
IOZR
TRI-STATE Output Current at Receiver
0.4V ≤ V
RIN
Receiver Input Resistance
−7V ≤ VIN ≤ +12V
ICC
No-Load Supply Current (Note 8)
DE = V
O
3
V
0.2
|V|
2.0
0
0
0
0
−7V ≤ VCM ≤ +12V
VCM = 0V
VOL
2.0
0
DI, DE, RE
(Note 1)
VIN = +12V
VIN = −7V
VTH
1.5
V
0.8
V
±2
µA
250
µA
−100 −200
µA
190
190
500
µA
−100 −400
µA
−0.2
0.2
70
RO
3.5
V
0.5
≤ 2.4V
±1
DS481
DS481T
=
,
RE
(Note
1)
0V or V
CC
A, B
48
V
mV
68
V
µA
kΩ
24
V CC
200
500
µA
200
500
µA
0.2
10
µA
CC
ICCX
Sleep Mode Supply Current
IOSD1
IOSD2
Driver Short Circuit Current, VO = HIGH
Driver Short Circuit Current, VO = LOW
IOSR
Receiver Short Circuit Current
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DE = 0V, RE (Note 1) = 0V or VCC
DE = GND
RE (Note 1) = VCC (Figure 14)
VCC
−7V ≤ VO ≤ +12V
A, B
−7V ≤ VO ≤ +12V
VO = GND
2
RO
7
250
mA
−250
mA
85
mA
Switching Characteristics
Over Supply Voltage and Operating Temperature Ranges, unless otherwise specified (Notes 5, 9, 10)
Symbol
Parameter
tPLHD
Driver Differential Propagation Delay — Low to High
tPHLD
Conditions
RL = 54Ω, CL = 100 pF
Min
Typ Max
Units
10
40
80
ns
Driver Differential Propagation Delay — High to Low
10
39
80
ns
tSKEW
Differential Skew |tPHLD − tPLHD|
0
1
10
ns
tr
Driver Rise Time
3
25
50
ns
tf
Driver Fall Time
3
25
50
ns
tZH
Driver Enable to Output High
50
200
ns
tZL
Driver Enable to Output Low
tLZ
Driver Disable from Output Low
tHZ
Driver Disable from Output High
tPSH
Driver Enable from Sleep
CL = 100 pF
CL = 100 pF
CL = 15 pF
Mode to Output High
tPSL
Driver Enable from Sleep
Mode to Output Low
65
200
ns
80
200
ns
CL = 15 pF
CL = 100 pF
80
200
ns
70
98
250
ns
(Note 12) (Figures 5, 6)
CL = 100 pF
70
98
250
ns
(Note 12) (Figures 7, 8)
CL = 15 pF (RO)
tPLHD
Receiver Differential Propagation Delay — Low to High
30
190
400
ns
tPHLD
Receiver Differential Propagation Delay — High to Low
30
210
400
ns
tSKEW
Differential Skew |tPHLD − tPLHD|
0
20
50
ns
tZH
Receiver Enable to Output High
45
150
ns
tZL
Receiver Enable to Output Low
40
150
ns
tLZ
Receiver Disable from Output Low
50
150
ns
tHZ
Receiver Disable from Output High
55
150
ns
tPSH
Receiver Enable from Sleep
CL = 15 pF
70
97
250
ns
Mode to Output High
(Note 12) (Figures 11, 13)
CL = 15 pF
70
95
250
ns
(Note 12) (Figures 11, 12)
DE = L and RE (Note 1) = H
50
600
ns
tPSL
CL = 15 pF
Receiver Enable from Sleep
Mode to Output Low
tSLEEP
Time to Sleep (Device)
(Figure 14)
fmax
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 VOD1/2/3and
VID.
Note 5: All typicals are given for: VCC = +5.0V, TA = +25˚C.
Note 6: ∆|VOD| and ∆|VOC| are changes in magnitude of V OD and VOC respectively, that occur when the input changes state.
Note 7: IIN2 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, tr and tf ≤ 6 ns, ZO = 50Ω.
Note 10: CL includes jig and probe capacitance.
Note 11: fmax 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/fmax). Using a 10% ratio yields fmax = (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. VOD
DS012919-6
FIGURE 5.
DS012919-7
DS012919-3
FIGURE 6.
FIGURE 2. VOD3
DS012919-4
FIGURE 3.
DS012919-8
FIGURE 7.
DS012919-9
FIGURE 8.
DS012919-5
DS012919-10
FIGURE 4.
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FIGURE 9.
4
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)
DS012919-15
*Note: Non Terminated, Open Input only
FIGURE 14. Entering Sleep Mode Conditions (modes and exit parameters shown)
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.
2
RE
(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.
7
DO
(Note 1)
/RI
(Note 1)
Driver Output/Receiver Input, 485 Bus Pin.
8
VCC
Positive Power Supply Connection: Recommended operating range for VCC is +4.75V to +5.25V.
option is selected. The 1⁄2 UL option is available in industrial
temperature and the 1⁄4 UL is available in commercial temperature.
First, for a 1⁄2 UL 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 a 1⁄4 UL 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 1⁄2 UL and 1⁄4 UL devices is the increased number of nodes on one bus. In a single master
Unit Load
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 −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 1⁄2 unit load and 1⁄4 unit load (UL) options
available. These devices will allow up to 64 nodes or 128
nodes guaranteed over temperature depending upon which
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6
Unit Load
Sleep Mode
(Continued)
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 tPSL and tPSH and compare
with tPZL and t PZH for timing differences.
The benefit of the DS481 is definitely its power savings.
When active the device has a maximum ICC of 500 µA.
When in sleep mode the device has a maximum ICC of only
10 µA, which is 50 times less power than when active. The
ICC when the device is active is already very low but when in
sleep mode the ICCis ultra low.
multi-slave type of application where the number of slaves
exceeds 32, the DS481 may save in the cost of extra devices
like repeaters, extra media like cable, and/or extra components like resistors.
DS012919-16
FIGURE 15. Input Current vs Input Voltage
Operating Range
Applications Information
(Continued)
Multipoint RS-485 Application
DS012919-17
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8
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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DS481 Low Power RS-485/RS-422 Multipoint Transceiver with Sleep Mode
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