LTC1487
Ultra-Low Power RS485
with Low EMI, Shutdown
and High Input Impedance
FEATURES
s
s
s
s
s
s
s
DESCRIPTIO
s
s
s
s
s
High Input Impedance: Up to 256 Transceivers
on the Bus
Low Power: I
CC
= 120µA Max with Driver Disabled
I
CC
= 200µA Max with Driver Enabled, No Load
1µA Quiescent Current in Shutdown Mode
Controlled Slew Rate Driver for Reduced EMI
Single 5V Supply
ESD Protection to
±10kV
On Receiver Inputs and
Driver outputs
– 7V to 12V Common-Mode Range Permits
±7V
Ground Difference Between Devices on the Data Line
Thermal Shutdown Protection
Power Up/Down Glitch-Free Driver Outputs Permit
Live Insertion or Removal of Transceiver
Driver Maintains High Impedance in Three-State
or with the Power Off
Pin Compatible with the LTC485
The LTC
®
1487 is an ultra-low power differential line trans-
ceiver designed with high impedance inputs allowing up to
256 transceivers to share a single bus. It meets the
requirements of RS485 and RS422. The LTC1487 features
output drivers with controlled slew rate, decreasing the
EMI radiated from the RS485 lines, and improving signal
fidelity with misterminated lines. The CMOS design offers
significant power savings without sacrificing ruggedness
against overload or ESD damage. Typical quiescent cur-
rent is only 80µA while operating and 1µA in shutdown.
The driver and receiver feature three-state outputs, with
the driver outputs maintaining high impedance over the
entire common-mode range. Excessive power dissipation
caused by bus contention or faults is prevented by a
thermal shutdown circuit which forces the driver outputs
into a high impedance state. The receiver has a fail-safe
feature which guarantees a high output state when the
inputs are left open. I/O pins are protected against multiple
ESD strikes of over
±10kV
using the Human Body Model.
The LTC1487 is fully specified over the commercial tem-
perature range and is available in 8-pin DIP and SO
packages.
, LTC and LT are registered trademarks of Linear Technology Corporation.
APPLICATI
s
s
s
S
Battery-Powered RS485/RS422 Applications
Low Power RS485/RS422 Transceiver
Level Translator
TYPICAL APPLICATI
LTC1487
1
RO
2
RE
3
DE
4
DI
R
7
D
6
120Ω
LTC1487
2000 FEET OF TWISTED-PAIR WIRE
7
120Ω
6
D
R
1
RO
2
RE
3
DE
4
DI
DI
RECEIVER INPUT
A
B
330Ω
4.7nF
RO
EQUIVALENT LOAD OF 256
LTC1487 TRANSCEIVERS
LTC1487 • TA01
U
LTC1487 • TA02
UO
UO
1
LINER [ LINEAR TECHNOLOGY ]
