NSC DS481TM

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 RS422 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.
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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 logichigh output if the input is open circuit.
The DS481 is available in a surface mount package and is
characterized for Industrial temperature range operation.
Connection and Logic Diagram
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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 64 tranceivers on the bus
Current-limiting and thermal shutdown for driver
overload protection
Industrial temperature range operation
Pin and functional compatible with MAX481C and
MAX481E
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
01291901
*Note: Non Terminated, Open Input only
Order Number
DS481TM
Temp. Range
−40˚C to +85˚C
Package/###
SOP/M08A
RE (Note
1)
DE
A-B
RO
L
L
L
≥+0.2V
H
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.
© 2004 National Semiconductor Corporation
DS012919
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DS481 Low Power RS-485/RS-422 Multipoint Transceiver with Sleep Mode
July 2000
DS481
Absolute Maximum Ratings (Note 3)
M Package
0.76W
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
Storage Temperature Range
Supply Voltage (VCC)
ESD (HBM)
(Soldering, 4 sec.)
+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)
Receiver Output Voltage (RO)
+260˚C
≥2 kV
Recommended Operating
Conditions
−14V to +14V
Receiver Input Voltage (A, B)
−65˚C to +150˚C
Lead Temperature Range
Min
−14V to +14V
Supply Voltage (VCC)
−0.5V to (VCC + 0.5V)
Max
Units
V
Operating Free Air
Maximum Package Power Dissipation @ +25˚C
M Package
Typ
+4.75 +5.0 +5.25
Temperature (TA)
1.19W
DS481T
Derate M Package 9.5 mW/˚C above +25˚C
−40
Bus Common Mode
Voltage
+25
−7
+85
˚C
+12
V
Maximum Package Power Dissipation @ +70˚C
Electrical Characteristics
Over Supply Voltage and Operating Temperature Ranges, unless otherwise specified (Notes 4, 5)
Symbol
Parameter
Conditions
Pin
Min Typ Max Units
A, B
1.5
VOD1
Differential Driver Output Voltage
(No Load)
VOD2
Differential Driver Output Voltage
RL = 50Ω, (RS422), Figure 1
2
2.8
with Load
RL = 27Ω, (RS485), Figure 1
1.5
2.3
Change in Magnitude of Output
RL = 27Ω or 50Ω (Note 6)
∆VOD
5
V
V
5
V
0.2
|V|
5
V
Differential Voltage
VOD3
Differential Driver Output Voltage —
R1 = 54Ω, R2 = 375Ω
Full Load with Max VCM
VTEST = −7V to +12V, Figure 2
1.5
VOC
Driver Common-Mode Output Voltage
RL = 27Ω or 50Ω, Figure 1
∆VOC
Change in Magnitude of Common-Mode
RL = 27Ω or 50Ω, Figure 1
Output Voltage
(Note 6)
2.0
0
3
V
0.2
|V|
VIH
Input High Voltage
VIL
Input Low Voltage
IIN1
Input Current
VIN = 0V or VCC
IIN2
Input Current (Note 7)
DE = 0V, VCC = 0V or 5.25V
VIN = +12V
VTH
Receiver Differential Threshold Voltage
−7V ≤ VCM ≤ +12V
∆VTH
Receiver Input Hysteresis
VCM = 0V
VOH
Receiver Output High Voltage
IO = −4 mA, VID = 0.2V
VOL
Receiver Output Low Voltage
IO = 4 mA, VID = −0.2V
0.5
V
IOZR
TRI-STATE Output Current at Receiver
0.4V ≤ V
±1
µA
RIN
Receiver Input Resistance
−7V ≤ VIN ≤ +12V
ICC
No-Load Supply Current (Note 8)
DE = V
DI, DE, RE
(Note 1)
DS481T
A, B
VIN = −7V
2.0
0
0
V
0.8
V
±2
µA
500
µA
−100 −400
µA
190
−0.2
0.2
70
O
CC,
RO
3.5
V
≤ 2.4V
DS481T
A, B
RE (Note 1) = 0V or V
V CC
V
mV
24
kΩ
200
500
µA
200
500
µA
0.2
10
µA
CC
DE = 0V, RE (Note 1) = 0V or VCC
ICCX
Sleep Mode Supply Current
IOSD1
Driver Short Circuit Current, VO = HIGH
−7V ≤ VO ≤ +12V
IOSD2
Driver Short Circuit Current, VO = LOW
−7V ≤ VO ≤ +12V
IOSR
Receiver Short Circuit Current
VO = GND
DE = GND
VCC
RE (Note 1)= VCC (Figure 14)
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2
A, B
RO
7
250
mA
−250
mA
85
mA
DS481
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
tSKEW
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
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
CL = 100 pF
50
200
ns
tZL
Driver Enable to Output Low
CL = 100 pF
65
200
ns
tLZ
Driver Disable from Output Low
CL = 15 pF
80
200
ns
tHZ
Driver Disable from Output High
CL = 15 pF
tPSH
Driver Enable from Sleep
CL = 100 pF
Mode to Output High
(Note 12) (Figures 5, 6)
Driver Enable from Sleep
CL = 100 pF
tPSL
Mode to Output Low
(Note 12) (Figures 7, 8)
tPLHD
Receiver Differential Propagation Delay — Low to High
CL = 15 pF (RO)
tPHLD
Receiver Differential Propagation Delay — High to Low
tSKEW
Differential Skew |tPHLD − tPLHD|
tZH
Receiver Enable to Output High
tZL
80
200
ns
70
98
250
ns
70
98
250
ns
30
190
400
ns
30
210
400
ns
20
50
ns
45
150
ns
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)
70
95
250
ns
600
ns
tPSL
0
CL = 15 pF
Receiver Enable from Sleep
CL = 15 pF
Mode to Output Low
(Note 12) (Figures 11, 12)
tSLEEP
Time to Sleep (Device)
DE = L and RE (Note 1) = H
fmax
Maximum Data Rate
(Note 11)
50
(Figure 14)
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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DS481
Parameter Measurement
Information
01291906
01291902
FIGURE 5.
FIGURE 1. VOD
01291907
FIGURE 6.
01291903
FIGURE 2. VOD3
01291908
01291904
FIGURE 7.
FIGURE 3.
01291909
FIGURE 8.
01291910
01291905
FIGURE 9.
FIGURE 4.
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DS481
01291911
FIGURE 10.
01291912
FIGURE 11.
01291913
FIGURE 12.
01291914
FIGURE 13.
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DS481
Parameter Measurement Information
(Continued)
01291915
*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.
The DS481 has 1⁄2 unit load and will allow up to 64 nodes
guaranteed over temperature.
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 ). 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 ).
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.
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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 TRISTATE. Refer to datasheet specifications tPSL and tPSH and
compare with tPZL and t PZH for timing differences.
(Continued)
The advantage of the 1⁄2 UL device 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
DS481 may save in the cost of extra devices like repeaters,
extra media like cable, and/or extra components like resistors.
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.
01291916
FIGURE 15. Input Current vs Input Voltage
Operating Range
Applications Information
Sleep Mode
The DS481 features an automatic sleep mode that allows
the device to save power when not transmitting data. Since
Multipoint RS-485 Application
01291917
7
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DS481
Unit Load
DS481 Low Power RS-485/RS-422 Multipoint Transceiver with Sleep Mode
Physical Dimensions
inches (millimeters)
unless otherwise noted
Order Number DS481TM
NS Package Number M08A
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.
For the most current product information visit us at www.national.com.
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