DS1485 High-Speed RS-485/RS-422 Multipoint Transceiver
September 1997
DS1485
High-Speed RS-485/RS-422 Multipoint Transceiver
General Description
The DS1485 is a high-speed low power transceiver for RS-
485 and RS-422 communication. The device contains one
driver and one receiver. The driver鈥檚 output transition time
supports operation up to 40 Mbps while minimizing power
consumption.
The transceiver draws 5mA of supply current when unloaded
or fully loaded with the driver disabled and operates from a
single +5V supply.
The driver is short-circuited current limited and is protected
against excessive power dissipation by thermal shutdown
circuitry that places the driver outputs into TRI-STATE
廬
(High Impedance state) under faut conditions. The driver
guarantees a minimum of 1.5V differential output voltage
with maximum loading across the common mode range
(V
OD3
).
The receiver incorporates a fail safe circuit which guarantees
a logic high output state when the inputs are left open. (Note
1)
The DS1485 is available in surface mount and DIP packages
and is characterized for Industrial (鈭?0藲C to +85藲C) and
Commercial temperature range operation.
Features
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Meets TIA/EIA RS-485 Multipoint Standard
Supports 40 Mbps operation
Guaranteed Full Load Output Voltage (V
OD3
)
Low Quiesent Current 5mA typ
鈭?V to +12V Common鈭扢ode Input Voltage Range
TRI-STATE Outputs on Driver and Receiver
AC Performance:
鈭?Driver Transition Time 3ns typ
鈭?Driver Propagation Delay 7ns typ
鈭?Driver Skew 0.2ns typ
鈭?Receiver Propagation Delay 3ns typ
鈭?Receiver Skew 0.3ns typ
Half鈭扗uplex Flow Through Pinout
Operates from a single 5V supply
Allows up to 32 Transceivers on the Bus
Current鈭扡imiting and Thermal Shutdown for Driver
Overload Protection
Industrial temperature range: 鈭?0藲C to +85藲C
鹵
10kV ESD (human body model) Protection on Bus
Pins
Pin and Functional Compatibility with ADM1485,
MAX485, LTC1485, SN75LBC176 and SN75ALS176B
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Connection and Logic Diagram
Truth Table
DRIVER SECTION
RE*
X
X
X
RE*
DE
H
H
L
DE
L
L
L
L
DI
H
L
X
RI鈭扲I
*
鈮?/div>
+0.2V
鈮?/div>
鈭?.2V
X
OPEN (Note 1)
DO/RI
H
L
Z
DO
*
/RI
*
L
H
Z
RO
H
L
Z
H
RECEIVER SECTION
DS100079-1
L
L
H
L
Order Number DS1485TM, DS1485TN,
DS1485M, DS1485N
See NS Package Number M08A or N08E
Note 1:
Non-terminated, open input only
TRI-STATE
廬
is a registered trademark of National Semiconductor Corporation.
漏 1999 National Semiconductor Corporation
DS100079
www.national.com
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