概述
数据手册ISO422P 概述
DIFFERENTIAL BUS TRANSCEIVER 差动总线收发器
ISO422P 数据手册
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®
ISO422
ISO422
DIFFERENTIAL BUS TRANSCEIVER
DESCRIPTION
FEATURES
ISO422 provides 1500Vrms isolation for industrial
bus transmission systems. ISO422 may be configured
in full or half duplex modes providing the user with
best flexibility for the application. Transmission rates
of 2.5Mbps can be obtained covering most require-
ments. A loop-back test facility is included. LBE
allows data on the D input to be routed to the R output
for test purposes.
● FULL-/HALF-DUPLEX OPERATION
● 1500Vrms ISOLATION (cont)
● 2500Vrms ISOLATION (1 min)
● 2.5Mbps PERFORMANCE
● LOOP-TEST FACILITY
APPLICATIONS
● BUS TRANSMISSION SYSTEMS
ISO422 is available in 24-pin PDIP and 24-pin Gull
Wing(1) packages and is specified over the temperature
range –40°C to +85°C.
● GROUND LOOP ISOLATION
NOTE: (1) Gull Wing version available Q1’99.
DE
Y
Z
D
LBE
R
A
B
RE
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 Internet: http://www.burr-brown.com/
•
•
Cable: BBRCORP Telex: 066-6491
•
•
FAX: (520) 889-1510 Immediate Product Info: (800) 548-6132
•
©1998 Burr-Brown Corporation
PDS-1503A
Printed in U.S.A. December, 1998
SPECIFICATIONS
At TA = +25°C, and VS = +5V, unless otherwise noted.
ISO422P, P-U(1)
TYP
PARAMETER
ISOLATION
CONDITIONS
MIN
MAX
UNITS
Rated Continuous Isolation
Partial Discharge Voltage
Barrier Impedance
VISO
50Hz, 60Hz
1s, 5 x 5pC/per cycle(2)
1500
2500
V
V
> 1014 || 10
1
Ω || pF
µA
Leakage Current
240V, 60Hz
2500V, 50Hz
10
1
µA
Creepage Distance
8.6
0.1
mm
mm
µs
Internal Isolation Distance
Transient Recovery Time
5kV/µs Edge
DRIVER DC CHARACTERISTICS
High Level Input Voltage
Low Level Input Voltage
Input Leakage Current
VIH
VIL
IL
D and DE Inputs(3)
D and DE Inputs(3)
D and DE Inputs(3)
D and DE Inputs(3)
2
V
V
0.8
5
5
nA
pF
Input Capacitance
CIN
Output Voltage
Differential Output Voltage
VO
VOD
VY or VZ
IOY or IOZ = 0
0
1.5
5
5
V
V
RL = 100Ω
RL = 54Ω
RL = 100Ω or 54Ω(4)
2
3.6
2.8
±40
5
V
V
1.5
5
Change in Mag Diff Out Voltage
Common-Mode Output Voltage
Change in Mag CM Out Voltage
Output Current
∆|VOD
VOC
∆|VOC
IO
|
±200
3
mV
V
RL = 100Ω or 54Ω
|
RL = 100Ω or 54Ω(4)
VO = VCC2, Output Disabled
VO = 0V, Output Disabled
VO = VCC2, Continuous
VO = 0V, Continuous
±40
±10
±200
±1000
±1000
mV
nA
nA
mA
mA
±10
Short-Circuit Output Current
100
–110
DRIVER SWITCHING CHARACTERISTICS (Figure 6)
Differential Output Delay Time
Skew |tDDH - tDDL
tDD
RL = 54Ω
RL = 54Ω
RL = 54Ω
RL = 100Ω
RL = 100Ω
RL = 100Ω
RL = 100Ω
120
25
150
50
ns
ns
ns
ns
ns
ns
ns
|
Differential Output Transition Time
Output Enable Time to HIGH
Output Enable Time to LOW
Output Disable Time from HIGH
Output Disable Time from LOW
tDT
tDZH
tDZL
tDHZ
tDLZ
100
150
150
150
150
120
120
120
120
RECEIVER DC CHARACTERISTICS
High Level Output Voltage
Low Level Output Voltage
Output Short-Circuit Current
Output HI-Z Leakage
VOH
VOL
IOS
IOZ
VIH
VIL
IL
IOH = 6mA
IOL = 6mA
VCC – 1
V
V
0.4
±1000
0.8
1s max
30
mA
nA
V
VOUT = 0V to VCC1
RE Input(3)
RE Input(3)
RE Input(3)
±10
Enable Input HIGH Threshold
Enable Input LOW Threshold
Input Leakage Current
2
V
5
nA
Input Capacitance
CIN
VTH
VTL
RE Input(3)
VO = 2.8V
VO = 0.4V
5
pF
mV
mV
mV
nA
V
Differential Input HIGH Threshold
Differential Input LOW Threshold
Input Hysteresis
Line Input Current
Line Voltage
100
–100
60
±10
±12
200
–200
1
See Note 5
Power On (GNDB < VBI < VSB
Power Off (IBI ±10mA max)
IBI
VBI
RIN
)
±1000
Input Resistance
MΩ
RECEIVER SWITCHING CHARACTERISTICS (Figure 7)
Propagation Delay L to H
Propagation Delay H to L
tRLH
tRHL
VID = –1.5V to 1.5V, CL = 10pF
VID = 1.5V to –1.5V, CL = 10pF
120
120
40
150
150
ns
ns
ns
ns
ns
ns
ns
ns
ns
Skew |tRLH - tRHL
|
Output Rise Time
tR
tF
CL = 10pF
CL = 10pF
CL = 10pF
CL = 10pF
CL = 10pF
CL = 10pF
10
Output Fall Time
10
Output Enable Time to HIGH
Output Enable Time to LOW
Output Disable Time from HIGH
Output Disable Time from LOW
tRZH
tRZL
tRHZ
tRLZ
15
25
25
25
25
15
15
15
®
ISO422
2
SPECIFICATIONS (CONT)
At TA = +25°C, and VS = +5V, unless otherwise noted.
ISO422P, P-U(1)
TYP
PARAMETER
POWER
CONDITIONS
MIN
MAX
UNITS
Supply Voltage—Data Side
Supply Current—Data Side
Supply Current—Data Side
VSA
ISA
4.5
5.5
13
V
Output Unloaded, dc
10
20
mA
mA
ISA
Output Unloaded, max Rate
Supply Voltage—Bus Side
Supply Voltage—Bus Side
VSB
ISB
4.5
5.5
20
V
mA
mA
Output Unloaded, dc
Output Unloaded, max Rate
12
20
BUS LIMITS
Input Current
±10
±5
mA
V
Maximum Differential Input
Maximum Data Rate
2.5
Mbps
TEMPERATURE RANGE
Operating
–40
–40
+85
°C
°C
Storage
+125
Thermal Resistance
θJA
75
°C/W
NOTES: (1) Gull Wing version available Q1’99. (2) All devices receive a 1s test. Failure criterion is > 5 pulses of > 5pC per cycle. (3) Logic inputs are HCT-type
and thresholds are a function of power supply voltage with approximately 100mV hysteresis. (4) Change in magnitude when the input is changed from HIGH to
LOW. (5) The difference between the differential low to high and high to low transition points.
ABSOLUTE MAXIMUM RATINGS
PIN CONFIGURATION
Supply Voltage: VSA ............................................................. –0.5V to +6V
VSB ............................................................. –0.5V to +6V
Top View
DIP
Continuous Isolation Voltage ..................................................... 1500Vrms
Storage Temperature ...................................................... –40°C to +125°C
Lead Temperature (soldering, 10s) ............................................... +300°C
DE
D
1
2
3
4
24 RE
23
R
PACKAGE INFORMATION
NC
VSA
22 LBE
PACKAGE DRAWING
21 GNDA
PRODUCT
PACKAGE
NUMBER(1)
ISO422P
ISO422P-U
24-Pin Plastic DIP
24-Pin Gull Wing Surface Mount
243-4
243-5
NOTE: (1) For detailed drawing and dimension table, please see end of data
sheet, or Appendix C of Burr-Brown IC Data Book.
GNDB
9
16 VSB
15 VSB
ELECTROSTATIC
GNDB 10
DISCHARGE SENSITIVITY
Y
Z
11
12
14
13
A
B
Electrostatic discharge can cause damage ranging from per-
formance degradation to complete device failure. Burr-
Brown Corporation recommends that all integrated circuits
be handled and stored using appropriate ESD protection
methods.
ESD damage can range from subtle performance degrada-
tion to complete device failure. Precision integrated circuits
may be more susceptible to damage because very small
parametric changes could cause the device not to meet
published specifications.
The information provided herein is believed to be reliable; however, BURR-BROWN assumes no responsibility for inaccuracies or omissions. BURR-BROWN
assumes no responsibility for the use of this information, and all use of such information shall be entirely at the user’s own risk. Prices and specifications are subject
to change without notice. No patent rights or licenses to any of the circuits described herein are implied or granted to any third party. BURR-BROWN does not
authorize or warrant any BURR-BROWN product for use in life support devices and/or systems.
®
ISO422
3
TYPICAL PERFORMANCE CURVES
At TA = +25°C, and VS = +5V, unless otherwise noted.
BUS 0 TO 1 TRANSITION
PROPAGATION DELAY
Y-Z
Z
D
Y-Z
Y
2µs/div
20ns/div
BUS 1 TO 0 TRANSITION
TERMINATED 200m CABLE
Y-Z
Y-Z
Z
Y
Z
Y
20ns/div
50ns/div
2kΩ RESISTORS INSERTED IN TERMINATED CABLE
Y-Z
Z
Y
200ns/div
®
ISO422
4
active. The receive enable/disable time is simply the time to
enable/disable the R output (tRLZ) and does not require any
additional barrier transmission time.
OPERATION
ISO422 is an isolated, full-duplex bus transceiver which is
compatible with three-wire data bus systems using EIA
standards RS-422-Aand RS-485. It is based on Burr-Brown’s
capacitive barrier technology. The data bus input is designed
to present a very high impedance to the data bus, thus
allowing a virtually unlimited number of receivers on any
data bus section. To allow this feature, the data bus input is
limited to a common-mode range within the magnitude of
the supplies. This limitation requires that all nodes on the
bus are referenced to a common ground. However, systems
attached to the bus through ISO422, are isolated up to
1500Vrms and may, therefore, have local floating ground
potentials up to this isolation voltage. The circuit encodes all
data passed across the barrier to ensure that the input values
and control signals are correctly passed across the barrier
under all power up conditions. The ISO422 also allows data
recovery to the current input state, after any transient upset.
RE
tRZH
tRLZ
tRZL
tRZH
R
tRLH
tRHL
A
B
FIGURE 2. ISO422 Data Receive.
DATA CORRUPTION
TRANSMIT
If, due to transient upset, the data passed across the barrier
is corrupted, the data will be restored within 100ns from the
end of the corrupting signal.
Data is passed from the D input to the data bus outputs after
a barrier transmission delay (tDD) when the DE input is
HIGH. When DE is LOW, the data bus drivers are switched
off, and assume the high impedance state. When enabling
the data bus output, i.e., switching DE from LOW to HIGH,
the enable signal is passed directly across the barrier and
enables the output, after a barrier transmission delay and
output enable time (tDLZ/tDHZ). Similarly, when disabling the
data bus output, i.e., switching DE from HIGH to LOW, the
disable signal is passed directly across the barrier and
disables the output after a barrier transmission delay and
output disable time (tDLZ/tDHZ).
SYNCHRONIZATION
The data transmitted across the barrier is coded using an
internal clock. This clock also captures the incoming asyn-
chronous data and synchronizes it to the clock edges. This
will give rise to an rms propagation delay jitter of approxi-
mately 50ns.
LOOPBACK
A loopback function is provided by the LBE input. If this
input is HIGH, then enabling both the transmitter and the
receiver will cause the device to route the D input to the R
output, in addition to the data bus outputs. Data on the
incoming bus is ignored. This feature allows a simple con-
nection test to be performed during any application. When
LBE is LOW, transmit and receive will operate in the normal
full-duplex mode.
DE
D
tDD
tDD
tDLZ
tDHZ
tDZH
tDZL
Y
Z
DATA BUS CONNECTION
ISO422 can be used in half duplex, or full duplex data
communication bus systems. It is capable of continuously
driving a 54Ω load, equivalent to a double-terminated trans-
mission line, at the fully specified data rate. When connect-
ing to the data bus, the voltage on the A and B input lines
must remain between VSB and GNDB. This can be achieved
by using a common bus ground connection, such as GNDB,
as shown in Figures 5 and 6.
FIGURE 1. ISO422 Data Transmit.
RECIEVE
The receive data is determined by the data bus differential
signal after a barrier transmission delay (tRZL). When the
difference between the A input and the B input (A-B) is
greater than +200mV, the R output will be HIGH. If A-B is
more negative than –200mV, the R output is undefined.
Since the reciver has a high impedance input, no disable
signal is required for the data bus input, which is always
For any system connected to the bus, the isolation provided
by ISO422 allows the independent local ground potential to
be as high as 1500Vrms with respect to the date bus ground
reference. This feature replaces the limited +12V to –7V
range of the RS-485 standard with the full-isolation voltage
capability of the ISO422.
®
ISO422
5
DE
D
1
2
3
4
24 RE
23
DE
D
1
2
3
4
24 RE
23
R
R
NC
VCC
22 LBE
NC
VCC
22 LBE
21 GNDA
21 GNDA
GNDB
9
16 VCC
15 VCC
GNDB
9
16 VCC
15 VCC
GNDB 10
GNDB 10
Y
Z
11
12
14
13
A
B
Y
Z
11
12
14
13
A
B
Loopback Enabled
Transmit and Receive Active
Loopback Disabled
Transmit and Receive Active
FIGURE 3. Loopback.
CONNECTION TO CAN BUS
Since the bus can be enabled and disabled at the same rate
as the data (2.5MHz), it is possible to use ISO422 as an
isolated bus driver in CAN systems. Again, the ISO422 bus
line must be constrained within the supply voltages.
DE
D
Y
Z
CANH
CANL
Figure 4 shows the connections which allow ISO422 to be
used in CANbus systems. The DE input of the ISO422 is
used as the CAN TX0 input and is used to transmit the data
by enabling and disabling the Y and Z outputs. The D and
RE inputs of the ISO422 are tied to GNDA. This ensures that
the Y output can only pull down, and the Z output can only
pull up. With D tied to GNDA, the DE input of ISO422 (TX0
of CAN) activates the Y output as an open drain pull-down
driver, and activates the Z output as an open drain pull-up
driver. Therefore, the Y line acts as CANL and the Z line acts
as CANH. When DE (TX0) is HIGH, ISO422 makes the bus
state dominant i.e., Y pulls LOW and Z pulls HIGH. With
DE (TX0) LOW, Y and Z are high impedance and the bus
state is recessive. Data is received in the normal manner
which is half duplex. Line Ais connected to CANH, and line
B is connected to CANL. The R output becomes RX0. RE
is tied to GNDA to keep R (RX0) enabled. If required, RE
may be used to disable the RX0 output.
TX0
RX0
A
B
R
RE
ISO422
FIGURE 4. CANBus Connection.
TX0
CANH
CANL
BUS
RX0
H
L
H
L
Dominant
Recessive
L
Hi-Z
Hi-Z
H
TABLE I. CAN.
®
ISO422
6
Shielded Twisted Pair EIA485
GNDB
GNDB
FIGURE 5. Half-Duplex Connection.
Shielded Twisted Pair EIA485
GNDB
GNDB
FIGURE 6. Full-Duplex Connection.
®
ISO422
7
R
120Ω
1.2kΩ
1.2kΩ
Half-duplex and Full-duplex resistor
values are the same. Half-duplex line
should be terminated at both ends.
Half Duplex
Full Duplex
FIGURE 7. Suggested Bus Termination Methods.
+5V
+5V
MAX202
MAX202
+5V Isolated
+5V Isolated
1.2kΩ(1)
1.2kΩ(1)
8
7
9
10
7
8
R
120Ω
10
9
R
120Ω
D9 D25
3
2
5
4
6
1
7
8
2
3
7
TD
RD
SG
RD
1.2kΩ(1)
1.2kΩ(1)
ISO422
ISO422
TD
SG
20 DTR
DTR
DSR
CD
6
8
4
5
DSR
CD
GNDA
GNDB
GND Isolation
GND Isolation
RTS
CTS
RTS
CTS
NOTE: (1) If using screened cable or ground
wire, connected as shown, shaded resistors
may be omitted. If using only twisted pairs,
shaded resistors are recommended.
FIGURE 8. Isolated RS232 to RS422. Null Modem Configuration.
®
ISO422
8
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