
ISO485
ISO485
Isolated RS-485
DIFFERENTIAL BUS TRANSCEIVER
International Airport Industrial Park Mailing Address: PO Box 11400 Tucson, AZ 85734 Street Address: 6730 S. Tucson Blvd. Tucson, AZ 85706
Tel: (520) 746-1111 Twx: 910-952-1111 Cable: BBRCORP Telex: 066-6491 FAX: (520) 889-1510 Immediate Product Info: (800) 548-6132
TRUTH TABLE
RS-485
BUS
DE
RE
0
0
R
X
0
1
HIGH Z
1
0
HIGH Z
1
1
T
X
FEATURES
G
RS-485 AND RS-422 COMPATIBLE
G
100% TESTED FOR HIGH-VOLTAGE
BREAKDOWN
G
RATED 1500Vrms
G
SINGLE-WIDE 24-PIN PLASTIC DIP
G
EASY TO USE
G
LOW POWER: 180mW typ at 5Mbit/s
APPLICATIONS
G
MULTIPOINT DATA TRANSMISSION
ON LONG BUS LINES IN NOISY
ENVIRONMENTS
DESCRIPTION
The ISO485 differential, isolated bus transceiver uses
Burr-Brown’s capacitively coupled isolation technol-
ogy to provide high-speed, low cost bus isolation.
The ISO485 is designed for bi-directional data com-
munication on multipoint bus transmission lines and
meets EIA Standard RS-485 as well as EIA Standard
RS-422A requirements.
The ISO485 uses high voltage 0.4pF capacitors in-
stead of the LED and photodetector which are used in
equivalent optocoupler solutions. As a consequence
the part count of the isolated RS-485 channel is
reduced from multiple optocoupler channels, an RS-
485 transceiver chip and supporting circuitry to one
ISO485. The capacitors in the ISO485 provide a high
voltage barrier, 1500Vrms and greatly reduce current
spikes on the power line.
The ISO485 combines a 3-state differential line driver
and a differential-input line receiver both of which
operate from a single 5V power supply. The driver
differential outputs and the receiver differential input/
output bus ports are designed to offer minimum load-
ing to the bus whenever the driver is disabled or
V
S
= 0V.
RE
A
B
D
R
DE
V
SA
22
23
24
11
14
3
2
1
V
SB
15
12
13
GB
GND
A
1994 Burr-Brown Corporation
PDS-1280C
Printed in U.S.A. May, 1995