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DS1487 Datasheet(PDF) 1 Page - National Semiconductor (TI)

[Old version datasheet] Texas Instruments acquired National semiconductor.
Part No. DS1487
Description  Low Power RS-485 1⁄4 Unit Load Multipoint Transceiver
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Maker  NSC [National Semiconductor (TI)]
Homepage  http://www.national.com
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DS1487 Datasheet(HTML) 1 Page - National Semiconductor (TI)

   
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DS1487
Low Power RS-485 14 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 14 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 (14 U.L.)
n Guaranteed full load output voltage (VOD3)
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
Order Number
Temp. Range
Package/###
DS1487N
0˚C to +70˚C
DIP/N08E
DS1487M
0˚C to +70˚C
SOP/M08A
Truth Table
DRIVER SECTION
RE
(Note 1)
DE
DI
A
B
X
HHH
L
XH
L
L
H
XLX
ZZ
RECEIVER SECTION
RE
(Note 1)
DE
A-B
RO
LL
≥+0.2V
H
LL
≤−0.2V
L
HX
X
Z
L
L
OPEN (Note 1)
H
X = indeterminate
Z = TRI-STATE
Note 1: Non Terminated, Open Input only
TRI-STATE® is a registered trademark of National Semiconductor Corporation.
DIP and SOIC
DS012920-1
*Note: Non Terminated, Open Input only
July 1998
© 1999 National Semiconductor Corporation
DS012920
www.national.com


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