LTC1535 Datasheet, PDF (1/12 Pages) Linear Technology – Isolated RS485 Transceiver

Final Electrical Specifications
LTC1535
Isolated RS485 Transceiver
August 1999
FEATURES
s _{UL Rated Isolated RS485: 2500VRMS}
s _{Half- or Full-Duplex}
s _{Eliminates Ground Loops}
s _{350kBd Maximum Data Rate}
s _{Self-Powered with 400kHz Converter}
s _{Fail-Safe Output High for Open or}
Shorted Receiver Inputs
s _{Short-Circuit Current Limit}
s _{Slow Slew Rate Control}
s _{68kΩ Input Impedance Allows Up to 128 Nodes}
s _{Thermal Shutdown}
s _{8kV ESD Protection On Driver Outputs and Receiver}
Inputs
U
APPLICATIO S
s _{Isolated RS485 Receiver/Driver}
s _{RS485 with Large Common Mode Voltage}
s _{Breaking RS485 Ground Loops}
s _{Multiple Unterminated Line Taps}
DESCRIPTIO
The LTC^®1535 is an isolated RS485 full-duplex differential
line transceiver. Isolated RS485 is ideal for systems where
the ground loop is broken to allow for much larger com-
mon mode voltage ranges. An internal capacitive isolation
barrier provides 2500V_RMS of isolation between the line
transceiver and the logic level interface. The powered side
contains a 400kHz push-pull converter to power the iso-
lated RS485 transceiver. Internal full-duplex communica-
tion occurs through the capacitive isolation barrier. The
transceiver meets RS485 and RS422 requirements.
The driver and receiver feature three-state outputs, with
the driver maintaining high impedance over the entire
common mode range. The drivers have short-circuit cur-
rent limits in both directions and a slow slew rate select to
minimize EMI or reflections. The 68kΩ receiver input
allows up to 128 node connections. A fail-safe feature
defaults to a high output state when the receiver inputs are
open or shorted.
, LTC and LT are registered trademarks of Linear Technology Corporation.
TYPICAL APPLICATIO
**
CTX02-14659
1/2 BAT54C
2
+
10µF
V_{CC +}
10µF
2
1
V_CC ^ST1
1
RO
28 ^RO
RE
27 ^RE
DE
26 ^DE
DI
25 ^DI
4 GND
1
LOGIC COMMON
1
3
ST2
400kHz
1/2 BAT54C
2
11
14
GND2 V_CC2
A
16
R
B
15
RO2
17
Y
13
D
Z
12
SLO
18
1535 TA01
FLOATING RS485 COMMON ** TRANSFORMER
COILTRONICS [phone]
2
TWISTED-PAIR
CABLE
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no represen-
tation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
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