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PDF ISO485P Data sheet ( Hoja de datos )
| Número de pieza | ISO485P | |
| Descripción | Isolated RS-485 DIFFERENTIAL BUS TRANSCEIVER | |
| Fabricantes | Burr-Brown Corporation | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de ISO485P (archivo pdf) en la parte inferior de esta página. Total 11 Páginas | ||
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® ISO485
ISO485
Isolated RS-485
DIFFERENTIAL BUS TRANSCEIVER
FEATURES
q RS-485 AND RS-422 COMPATIBLE
q 100% TESTED FOR HIGH-VOLTAGE
BREAKDOWN
q RATED 1500Vrms
q SINGLE-WIDE 24-PIN PLASTIC DIP
q EASY TO USE
q LOW POWER: 180mW typ at 5Mbit/s
APPLICATIONS
q MULTIPOINT DATA TRANSMISSION
ON LONG BUS LINES IN NOISY
ENVIRONMENTS
RE
2
R
1
3 VSA
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
VS = 0V.
15 VSB
A 12
B 13
D
24
DE
23
GND
A
22
11 14
GND
B
TRUTH TABLE
RS-485
DE RE
BUS
00
01
RX
HIGH Z
1 0 HIGH Z
11
TX
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
©1994 Burr-Brown Corporation
PDS-1280C
Printed in U.S.A. May, 1995
1 page  
TYPICAL PERFORMANCE CURVES
At TA = +25°C, VS = +5V, unless otherwise noted.
100m
ISOLATION LEAKAGE CURRENT vs FREQUENCY
10m
1m
100µ
VISO = 1500Vrms
10µ
1µ
100n
1
VISO = 240Vrms
10 100 1k 10k 100k 1M
Frequency (Hz)
TYPICAL INSULATION RESISTANCE vs TEMPERATURE
1016
1015
1014
1013
1012
1011
1010
0
20 40 60 80 100 120 140 160 180
Temperature (°C)
ISOLATION VOLTAGE vs FREQUENCY
10k Max DC
Rating
2.1k
1k Degraded
Performance
100
10
1
1k
10k 100k 1M
10M
100M
Frequency (Hz)
PROPAGATION DELAY vs TEMPERATURE
60
CL = 50pF
50
40
30
VS = 5.0V
20
10
0
–60 –40 –20
0 20 40 60 80 100 120 140
Temperature (°C)
NORMALIZED RISE/FALL TIME vs TEMPERATURE
1.6
1.5
1.4 CL = 50pF
+1σ
1.3 Normalized to Average
of Many Devices
1.2 at 25°C
1.1
1.0
0.9
–60 –40 –20
–1σ
0 20 40 60 80 100 120 140
Temperature (°C)
TYPICAL POWER DISSIPATION vs DATA RATE
500
400
Transmit
300
NOTE:
Baud Rate = 2 • Frequency
200
Receive
100
0
100k
1M 10M
Data Rate (Mbit/s)
100M
®
5 ISO485
5 Page 
CLK I/P
U1
1A
2B
8 CLK
9
CLR
QA
QB
QC
3
4
5
6
QD
QE
QF
10
11
12
QG
QH
13
74ACT 164
U2
1
2
A
B
8
CLK
9 CLR
3
QA 4
QB 5
QC 6
QD
QE
10
11
QF 12
QG 13
QH
74ACT 164
U3B
4
6
5
74ACT 86
1 U3A
3
2
O/P 74ACT 86
FIGURE 7. NRZ Psuedo-Noise Generator.
+12
R1
D1
AA
PTC
PTC
U3C 9
8
10
74ACT 86
UA4
4
2 D PR Q 5
3 CLK
CL Q 6
1 74ACT 74
U4B
10
12 D PR Q 9
11 CLK
CL Q 8
13 74ACT 74
+VCC 5V
+12
R3
D2
RT RT
Z1
R2
Z3
Z2
Z4
BB
PTC
PTC
Z6 Z5
R4
Z8 Z7
NOTE: PTC = Positive Temperature Coefficient Thermistor.
FIGURE 8. RS-485 Line with Fail-Safe Protection.
a) R = R and R = R
13
24
For open circuit conditions this biases the line to a logic '1'
b) Z = Z = Z =Z = BZX85 = 12V
1 3 57
Z2 = Z4 = Z6 =Z8 = BZX85 = 6.8V
D =D = IN4048
12
The zener diode in conjunction with the ptc thermistors limit the current
drawn on the line when taken beyond the +12V and –7V. The ptc
thermistors also current limit on the line being shorted to the ground.
c)
R1
= R2
=
0. 5
×
Z0
1 +
V CC
V TH
RT
=
Z0
1 +
V TH
V CC
®
11 ISO485
11 Page | ||
| Páginas | Total 11 Páginas | |
| PDF Descargar | [ Datasheet ISO485P.PDF ] | |
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