概述
数据手册
替代型号DS485TM 概述
Low Power RS-485/RS-422 Multipoint Transceiver 低功耗RS - 485 / RS - 422收发器多
DS485TM 数据手册
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PDF下载July 1998
DS485
Low Power RS-485/RS-422 Multipoint Transceiver
General Description
Features
n Meets TIA/EIA RS-485 multipoint standard
The DS485 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
2.5 Mbps (see Applications Information section).
n Guaranteed full load output voltage (V
n Low quiescent current: 200 µA typ
)
OD3
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 32 transceivers on the bus
n Current-limiting and thermal shutdown for driver
overload protection
The transceiver draws 200 µA of supply current when un-
loaded or fully loaded with the driver disabled and 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 DS485 is available in surface mount and DIP packages
and is characterized for Industrial and Commercial tempera-
ture range operation.
n Industrial temperature range operation
n Pin and functional compatible with MAX485 and LTC485
Connection and Logic Diagram
Truth Table
DRIVER SECTION
DIP and SOIC
*
RE
X
DE
H
DI
H
L
A
H
L
B
L
X
H
H
Z
X
L
X
Z
RECEIVER SECTION
*
RE
L
DE
L
A-B
≥+0.2V
≤−0.2V
X
RO
H
DS012880-1
L
L
L
H
L
X
Z
Order Number
DS485N
Temp. Range
0˚C to +70˚C
Package/###
DIP/N08E
*
L
OPEN
H
*
Note: Non Terminated, Open Input only
DS485M
0˚C to +70˚C
SOP/M08A
DIP/N08E
=
X
Z
indeterminate
TRI-STATE
=
DS485TN
DS485TM
−40˚C to +85˚C
−40˚C to +85˚C
SOP/M08A
TRI-STATE® is a registered trademark of National Semiconductor Corporation.
© 1999 National Semiconductor Corporation
DS012880
www.national.com
Absolute Maximum Ratings (Note 1)
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
N Package
0.47W
Storage Temperature Range
Lead Temperature Range
(Soldering, 4 sec.)
ESD (HBM)
−65˚C to +150˚C
+260˚C
≥2 kV
Supply Voltage (VCC
)
+12V
−0.5V to (VCC + 0.5V)
−0.5V to (VCC + 0.5V)
−14V to +14V
*
Enable Input Voltage (RE , DE)
Recommended Operating
Conditions
Driver Input Voltage (DI)
Driver Output Voltage (A, B)
Receiver Input Voltage (A, B)
Receiver Output Voltage (RO)
−14V to +14V
Min
Typ
Max Units
−0.5V to (VCC + 0.5V)
Supply Voltage (VCC
Operating Free Air
Temperature (TA)
DS485
)
+4.75 +5.0 +5.25
V
@
Maximum Package Power Dissipation +25˚C
M Package
1.19W
0.74W
N Package
0
+25
+25
+70
+85
+12
˚C
˚C
V
Derate M Package 9.5 mW/˚C above +25˚C
Derate N Package 6.0 mW/˚C above +25˚C
DS485T
−40
−7
Bus Common Mode Voltage
@
Maximum Package Power Dissipation +70˚C
M Package
0.76W
Electrical Characteristics
Over Supply Voltage and Operating Temperature Ranges, unless otherwise specified (Notes 2, 3)
Symbol
VOD1
Parameter
Differential Driver Output Voltage
Differential Driver Output Voltage
with Load
Conditions
Pin
Min Typ Max Units
(No Load)
A, B
5
V
V
=
VOD2
RL 50Ω, (RS422), Figure 1
2
2.8
=
RL 27Ω, (RS485), Figure 1
1.5 2.3
5
V
=
∆VOD
Change in Magnitude of Output
Differential Voltage
RL 27Ω or 50Ω (Note 4)
0.2
|V|
=
=
VOD3
Differential Driver Output Voltage —
Full Load with Max VCM
Driver Common-Mode Output Voltage
Change in Magnitude of Common-Mode
Output Voltage
R1 54Ω, R2 375Ω
1.5 2.0
5
V
=
VTEST −7V to +12V, Figure 5
=
VOC
RL 27Ω or 50Ω, Figure 1
3
V
=
∆VOC
RL 27Ω or 50Ω, Figure 1 (Note 4)
0.2
|V|
VIH
VIL
IIN1
IIN2
Input High Voltage
DI,
DE,
2.0
V
V
Input Low Voltage
0.8
*
RE
=
±
Input Current
VIN 0V or VCC
2
µA
mA
mA
V
=
Input Current (Note 5)
VIN +12V
A, B
1.0
−0.8
0.2
=
=
=
DE 0V, VCC 0V or 5.25V
Receiver Differential Threshold Voltage
Receiver Input Hysteresis
VIN −7V
VTH
∆VTH
VOH
VOL
IOZR
RIN
−7V ≤ VCM ≤ +12V
−0.2
=
VCM 0V
70
mV
V
=
=
Receiver Output High Voltage
Receiver Output Low Voltage
TRI-STATE Output Current at Receiver
Receiver Input Resistance
IO −4 mA, VID 0.2V
RO
3.5
12
=
=
IO 4 mA, VID −0.2V
0.4
V
±
0.4V ≤ VO ≤ 2.4V
1
µA
kΩ
µA
µA
mA
mA
mA
−7V ≤ VIN ≤ +12V
A, B
VCC
=
=
0V or VCC
*
ICC
No-Load Supply Current (Note 6)
DE VCC, RE
200
200
900
500
250
250
85
=
=
0V or VCC
*
DE 0V, RE
=
IOSD1
IOSD2
IOSR
Driver Short Circuit Current, VO HIGH
−7V ≤ VO ≤ +12V
−7V ≤ VO ≤ +12V
0V ≤ VO ≤ VCC
A, B
RO
35
35
7
=
Driver Short Circuit Current, VO LOW
Receiver Short Circuit Current
www.national.com
2
Switching Characteristics
Over Supply Voltage and Operating Temperature Ranges, unless otherwise specified (Notes 3, 7, 8)
Symbol
tPLHD
tPHLD
tSKEW
tr
Parameter
Conditions
Min
10
Typ
40
39
1
Max
65
Units
ns
= =
RL 54Ω, CL 100 pF
Driver Differential Propagation Delay — Low to High
Driver Differential Propagation Delay — High to Low
10
65
ns
Differential Skew |tPHLD − tPLHD
|
10
ns
Driver Rise Time
3
3
25
25
40
ns
tf
Driver Fall Time
40
ns
=
tZH
Driver Enable to Output High
Driver Enable to Output Low
CL 100 pF
170
170
170
170
320
320
50
ns
=
tZL
CL 100 pF
ns
=
tLZ
Driver Disable from Output Low
CL 15 pF
ns
=
tHZ
Driver Disable from Output High
CL 15 pF
ns
=
tPLHD
tPHLD
tSKEW
tZH
Receiver Differential Propagation Delay — Low to High
Receiver Differential Propagation Delay — High to Low
CL 15 pF (RO)
70
70
190
210
20
ns
ns
Differential Skew |tPHLD − tPLHD
|
ns
=
Receiver Enable to Output High
Receiver Enable to Output Low
Receiver Disable from Output Low
Receiver Disable from Output High
Maximum Data Rate
CL 15 pF
110
110
110
110
ns
tZL
ns
tLZ
ns
tHZ
ns
fmax
(Note 9)
2.5
Mbps
Note 1: “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 2: 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 3: All typicals are given for: V
=
=
A
+5.0V, T
+25˚C.
OD
includes the receiver input current and driver TRI-STATE leakage current.
CC
Note 4: ∆|V | and ∆|V | are changes in magnitude of V
and V respectively, that occur when the input changes state.
OC
OD OC
Note 5:
I
IN2
=
=
Note 6: Supply current specification is valid for loaded transmitters when DE 0V or enabled (DE H) with no load.
=
=
1 MHz, t and t ≤ 6 ns, Z
O
Note 7:
Note 8:
Note 9:
f
50Ω.
r
f
C
includes jig and probe capacitance.
L
f
is the guaranteed data rate for 50 ft of twisted pair cable. f
may be conservatively determined from the ratio of driver transition time (t ) to the data
max r
max
= =
rate unit interval (1/f
). Using a 10% ratio yields f
max
(0.1)/40 ns 2.5 Mb/s. Higher data rates may be supported by allowing larger ratios.
max
3
www.national.com
Parameter Measurement Information
DS012880-3
DS012880-2
FIGURE 5. VOD3
FIGURE 1. VOD
DS012880-4
FIGURE 2.
DS012880-5
FIGURE 6.
DS012880-6
FIGURE 3.
DS012880-7
FIGURE 7.
DS012880-9
FIGURE 8.
DS012880-8
FIGURE 4.
www.national.com
4
Parameter Measurement Information (Continued)
DS012880-10
FIGURE 9.
DS012880-11
FIGURE 10.
DS012880-12
FIGURE 11.
DS012880-13
FIGURE 12.
DS012880-14
FIGURE 13.
5
www.national.com
Parameter Measurement Information (Continued)
Pin Descriptions
Pin #
I/O
Name
Function
>
<
1
O
RO
Receiver Output: If A B by 200 mV, RO will be high; If A B by 200 mV, RO will be low. RO will
be high also if the inputs (A and B) are open (non-terminated).
*
*
*
2
3
I
I
RE
Receiver Output Enable: RO is enabled when RE is low; RO is in TRI-STATE when RE is high.
DE
Driver Output Enable: The driver outputs (A and B) are enabled when DE is high; they are in
TRI-STATE when DE is low. Pins A and B also function as the receiver input pins (see below).
4
I
DI
Driver Input: A low on DI forces A low and B high while a high on DI forces A high and B low when
the driver is enabled.
5
6
NA
I/O
GND
A
Ground
Non-inverting Driver Output and Receiver Input pin. Driver output levels conform to RS-485 signaling
levels.
7
8
I/O
NA
B
Inverting Driver Output and Receiver Input pin. Driver output levels conform to RS-485 signaling
levels.
VCC
Power Supply: 4.75V ≤ VCC ≤ 5.25V
Related National Low Power RS-485 Transceivers
Part Number
Temperature
Range
Number of
Comments
XCVRs on Bus
DS36C278
0˚C to +70˚C
−40˚C to +85˚C
0˚C to +70˚C
−40˚C to +85˚C
0˚C to +70˚C
−40˚C to +85˚C
128
64
Ultra Low Power Transceiver
Ultra Low Power Transceiver
Auto-Sleep Mode
DS36C278T
DS36C279
DS36C279T
DS36C280
DS36C280T
128
64
Auto-Sleep Mode
128
64
Adjustable Slew Rate Control
Adjustable Slew Rate Control
www.national.com
6
Applications Information
The DS485 is a low power transceiver designed for use in
RS-485 multipoint applications. The DS485 can transmit
data up to 2.5 Mbps based on a ratio of driver transition time
to the unit interval (bit time) of 10%. This maximum data rate
may be further limited by the interconnecting media. The
DS485 provides a standard unit load to the RS-485 bus
across the common mode range of −7V to +12V. This allows
up to 32 transceivers (standard unit load) to be connected to
the bus. More transceivers may be connected to the bus if
they support a reduced unit load (see DS36C278). The
DS485 also guarantees the driver’s output differential volt-
age into a worst case load that models standard termination
loads and 32 unit loads referenced to the maximum common
mode voltage extremes. With a minimum of 1.5V swing into
this load, a 1.3V differential noise margin is supported along
with the standard common mode rejection range of the re-
ceivers.
Due to the multipoint nature of the bus, contention between
drivers may occur. This will not cause damage to the drivers
since they feature short-circuit protection and also thermal
shutdown protection. Thermal shutdown senses die tem-
perature and puts the driver outputs into TRI-STATE if a fault
condition occurs that causes excessive power dissipation
which can elevate the junction temperature to +150˚C.
A typical multipoint application is shown in the following fig-
ure. Note that termination is typically required but is only lo-
cated at the two ends of the cable (not on every node). Com-
monly pull up and pull down resistors may be required at one
end of the bus to provide a failsafe bias. These resistors pro-
vide a bias to the line when all drivers are in TRI-STATE. See
National Application Note 847 for a complete discussion of
failsafe biasing of differention buses.
Multipoint RS-485 Application
DS012880-16
7
www.national.com
8
Physical Dimensions inches (millimeters) unless otherwise noted
Order Number DS485M or DS485TM
NS Package Number M08A
Order Number DS485N or DS485TN
NS Package Number N08E
9
www.national.com
LIFE SUPPORT POLICY
NATIONAL’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DE-
VICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT OF NATIONAL SEMI-
CONDUCTOR CORPORATION. As used herein:
1. Life support devices or systems are devices or sys-
tems which, (a) are intended for surgical implant into
the body, or (b) support or sustain life, and whose fail-
ure 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 rea-
sonably 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
National Semiconductor
Europe
National Semiconductor
Asia Pacific Customer
Response Group
Tel: 65-2544466
Fax: 65-2504466
National Semiconductor
Japan Ltd.
Tel: 81-3-5639-7560
Fax: 81-3-5639-7507
Fax: +49 (0) 1 80-530 85 86
Email: europe.support@nsc.com
Deutsch Tel: +49 (0) 1 80-530 85 85
English Tel: +49 (0) 1 80-532 78 32
Français Tel: +49 (0) 1 80-532 93 58
Italiano Tel: +49 (0) 1 80-534 16 80
Email: sea.support@nsc.com
www.national.com
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.
DS485TM 替代型号
| 型号 | 制造商 | 描述 | 替代类型 | 文档 |
| ADM485JNZ | ADI | 5 V, Low Power, 5 Mbps, Half Duplex EIA RS-485 Transceiver | 功能相似 |
|
DS485TM 相关器件
| 型号 | 制造商 | 描述 | 价格 | 文档 |
| DS485TM/NOPB | TI | Low-Power RS-485/RS-422 Multipoint Transceiver 8-SOIC -40 to 85 | 获取价格 |
|
| DS485TMX | ETC | Transceiver | 获取价格 |
|
| DS485TN | NSC | Low Power RS-485/RS-422 Multipoint Transceiver | 获取价格 |
|
| DS485TN/NOPB | TI | LINE TRANSCEIVER, PDIP8, PLASTIC, DIP-8 | 获取价格 |
|
| DS485TN/NOPB | ROCHESTER | LINE TRANSCEIVER, PDIP8, PLASTIC, DIP-8 | 获取价格 |
|
| DS49 | LUMILEDS | power light source LUXEON㈢ Flash | 获取价格 |
|
| DS4E-M-DC1.5V | NAIS | HIGHLY SENSITIVE 1500 V FCC SURGE WITHSTANDING MINIATURE RELAY | 获取价格 |
|
| DS4E-M-DC1.5V | PANASONIC | Power/Signal Relay, 4PDT, Momentary, 0.267A (Coil), 1.5VDC (Coil), 400mW (Coil), 2A (Contact), 30VDC (Contact), DC Input, AC/DC Output, Through Hole-Straight Mount, ROHS COMPLIANT | 获取价格 |
|
| DS4E-M-DC12V | NAIS | HIGHLY SENSITIVE 1500 V FCC SURGE WITHSTANDING MINIATURE RELAY | 获取价格 |
|
| DS4E-M-DC12V-R | PANASONIC | Power/Signal Relay, 4PDT, Momentary, 0.033A (Coil), 12VDC (Coil), 400mW (Coil), 2A (Contact), 220VDC (Contact), DC Input, AC/DC Output, Through Hole-Straight Mount | 获取价格 |
|
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