DS1487 Datasheet, PDF (1/8 Pages) National Semiconductor (TI) – Low Power RS-485 1⁄4 Unit Load Multipoint Transceiver

July 1998
DS1487
Low Power RS-485 ¹â„4 Unit Load Multipoint Transceiver
General Description
The DS1487 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 trans-
ceiver presents ¹â„4 unit loading to the RS-485 bus allowing up
to 128 nodes to be connected together without the use of re-
peaters.
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
(V_OD3).
The receiver has a failsafe feature that guarantees a
logic-high output if the input is open circuit.
The DS1487 is available in surface mount and DIP pack-
ages.
Features
n Meets TIA/EIA RS-485 multipoint standard
n Allows up to 128 transceivers on the bus (¹â„4 U.L.)
n Guaranteed full load output voltage (V_OD3)
n Low quiescent current: 200 µA 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 Current-limiting and thermal shutdown for driver
overload protection
n Pin and functional compatible with MAX1487
Connection and Logic Diagram
Truth Table
DIP and SOIC
DRIVER SECTION
RE
DE
DI
A
B
(Note 1)
X
H
H
H
L
X
H
L
L
H
X
L
X
Z
Z
RECEIVER SECTION
DS012920-1
RE
DE
A-B
RO
(Note 1)
*Note: Non Terminated, Open Input only
L
L
≥+0.2V
H
L
L
≤−0.2V
L
Order Number
Temp. Range
Package/###
H
X
X
Z
DS1487N
0˚C to +70˚C
DIP/N08E
L
L
OPEN (Note 1)
H
DS1487M
0˚C to +70˚C
SOP/M08A
X = indeterminate
Z = TRI-STATE
Note 1: Non Terminated, Open Input only
TRI-STATE^® is a registered trademark of National Semiconductor Corporation.
© 1999 National Semiconductor Corporation DS012920
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