LTC1535_2 Datasheet, PDF (1/18 Pages) Linear Technology – Isolated RS485 Transceiver

FEATURES
n _{UL Rated Isolated RS485: 2500VRMS}
UL Recognized ® File #E151738
n _{Eliminates Ground Loops}
n _{250kBd Maximum Data Rate}
n _{Self-Powered with 420kHz Converter}
n _{Half- or Full-Duplex}
n _{Fail-Safe Output High for Open or}
Shorted Receiver Inputs
n _{Short-Circuit Current Limit}
n _{Slow Slew Rate Control}
n _{68kΩ Input Impedance Allows Up to 128 Nodes}
n _{Thermal Shutdown}
n _{8kV ESD Protection On Driver Outputs and}
Receiver Inputs
n _{Available in 28-Lead SW Package}
APPLICATIONS
n _{Isolated RS485 Receiver/Driver}
n _{RS485 with Large Common Mode Voltage}
n _{Breaking RS485 Ground Loops}
n _{Multiple Unterminated Line Taps}
LTC1535
Isolated RS485 Transceiver
DESCRIPTION
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 common
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
420kHz push-pull converter to power the isolated RS485
transceiver. Internal full-duplex communication 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
current 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.
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear
Technology Corporation. All other trademarks are the property of their respective owners.
TYPICAL APPLICATION
**
CTX02-14659
1/2 BAT54C
2
+
10μF
V_{CC +}
10μF
2
1
V_CC ^ST1
LOGIC COMMON
RO
1
FLOATING RS485 COMMON
2
RE
** COOPER [phone]
DE
DI
1
28 ^RO
RE
27
26 ^DE
25 ^DI
4 GND
1
3
ST2
420kHz
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
TWISTED-PAIR
CABLE
1535fb
1