Burr-Brown ISC300 Universal precision isolated measurement channel Datasheet

®
ISC300
Universal Precision Isolated
MEASUREMENT CHANNEL
FEATURES
APPLICATIONS
● CALIBRATION CAPABILITY
● UNIVERSAL INPUT CHANNEL FOR
PROCESS CONTROL SYSTEMS
● ISOLATED MEASUREMENT CHANNEL
FOR THERMOCOUPLE, RTD AND
VOLTAGE TRANSDUCERS
● CHANNEL TO CHANNEL ISOLATED
MULTIPLEXED SYSTEMS
● ISOLATED 4 TO 20mA RECEIVER
●
●
●
●
●
●
INTEGRAL SENSOR EXCITATION
OPEN CIRCUIT SENSOR DETECTION
LOW POWER: 80mW
INSTRUMENT AMPLIFIER INPUT
PROGRAMMABLE GAIN
12-BIT LINEARITY
● TWO ISOLATED POWER SUPPLIES:
±13V at 5mA
● LOW DRIFT 10V REFERENCE
DESCRIPTION
The ISC300 is an isolated measurement channel with
open circuit sensor detection for use with RTD and
thermocouple temperature sensors. In addition to temperature measurement, the ISC300 can accept full
scale input voltages of ±100mV and ±10V which
allows use with other sensors such as pressure, humidity and flow sensors. The low level resistance measurement capability also allows stimulus and measure9
+VISO
2
–VISO
ment of strain gauges. The measurement channel has
a highly stable internal reference which can be selected from the output side. This allows the user to
calibrate each channel at the factory, record the calibration data and periodically recalibrate the system
while in use over time and ambient temperature
changes.
20M
8 Sense 2
5
+IP
6
–IP
Barrier
+VISO
Out
Filter
Channel 1 Out
PGA
Modulate
Demod
Rectify
Power
28
INPUT
SELECT
A1
A0
Com1
+0.1V
+10V
Signal
0
0
1
1
0
1
0
1
GAIN
SELECT
G
0.5
50
0
1
20M
3 Sense 1
–VISO
10.0V
Ref
1
IREF1
7
IREF2
0.100V
Current
Reference
Com 1
Com 1
CKI
26
Com 2
27
VDD (+5)
18
CLK
22
G
19
A0
20
A1
21
RST
23
DCom 2
24
Channel 3
R
–VISO
10
VCC (+15) 25
99R
VREF
4
MUX
Channel 2
Channel 4
A0
A1
O
P
T
O
Com 1
Input Side
Com 2
C
O
U
P
L
E
Output Side
L
A
T
C
H
SELECT
and GAIN
RST
CLK
No Change
No Change
Latch
RESET
1
1
1
0
0
1
^
X
International Airport Industrial Park • Mailing Address: PO Box 11400
Tel: (520) 746-1111 • Twx: 910-952-1111 • Cable: BBRCORP •
• Tucson, AZ 85734 • Street Address: 6730 S. Tucson Blvd. • Tucson, AZ 85706
Telex: 066-6491 • FAX: (520) 889-1510 • Immediate Product Info: (800) 548-6132
©
PDS-1135A
1991 Burr-Brown Corporation
Printed in U.S.A. October, 1993
SPECIFICATIONS
ELECTRICAL
At VCC = 15V, VDD = 5V, TA = +25°C, unless otherwise noted.
ISC300
PARAMETER
ISOLATION
Isolation Voltage (VISO)
Isolation Mode Rejection (IMR)
Barrier Impedance
Leakage Current (IISO)
GAIN
Voltage Gains
Resistance Conversion
Initial Error
vs Temperature
Nonlinearity
INPUT OFFSET VOLTAGE
Initial Offset (Input Referred)
CONDITIONS
MIN
AC60Hz Continuous
AC60Hz Continuous
VISO, DC
Partial Discharge(1)
VISO = Rated 60Hz Cont(2)
500
±700
700
800
110
TYP
±30
±0.01
0°C to +70°C
VO = –5V to +5V(4)
vs Supply (VCC)
±1.5
–40°C to +85°C
35
100
Resistance Range
Peak Voltage
Impedance: Differential
Common Mode Rejection
Source Impedance Imbalance
OUTPUT
Voltage Range
Overrange Voltage
Output Impedance
Ripple Voltage
FREQUENCY RESPONSE
Input Bandwidth
Input Settling Time
Input Overload Recovery
Output Overload Settling Time
Output Overload Recovery
VOLTAGE REFERENCE
VREF1 (Internal and External)
Initial Accuracy
vs Temperature
vs Time
vs Supply (VCC)
VREF2 (Internal)
Initial Accuracy(6)
vs Temperature
vs Time
vs Supply (VCC)
POWER SUPPLIES
Analog Supply Range
Supply Current
Digital Supply Range
Supply Current
Total Power Dissipation
Isolated Supplies: Voltage
Current
Rated Operation G = 0.5V Input
Rated Operation G = 50V Input
Rated Operation G = 50 3-wire Resistance
Applied to Any Signal Input Wrt Com 1(5)
CMR at DC Gain = 0.5(3)
CMR at DC Gain = 50(3)
CMR at 60Hz(3)
For Normal Operation < 1kΩ Imbalance
Min Load = 1MΩ
During Input Fault (VIN < –11V or VIN > 11V)
0
10
66
75
60
±3
±50
±0.025
V/V
mV/Ω
%
ppm/°C
%
nA
pA/°C
±10
±0.1
500
±380
V
V
Ω
V
MΩ
dB
dB
dB
kΩ
3
0.5
10
V
V
kΩ
mVrms
mVp-p
3.5
0.5
5
1
2
Hz
s
s
ms
ms
100
±0.1
±10
14
5
4
11.5
2
50
±5
10
±0.1
±10
External Loading of 100nA
No External Load
at 5mA Each Supply
mV
mV
µV/°C
µV/°C
mV/V
75
100
70
±5.4
TSETT, to within 5% for VIN < 14V
VCC Pin
No External Load
VDD Pin
±200
±5
±200
±5
10
f = 0 to 5kHz Min Load 1MΩ
f = 0 to 100kHz Min Load 1MΩ
®
ISC300
4
Vrms
VPEAK
V
Vrms
dB
GΩ || pF
µArms
50, 0.5
10
INPUT CURRENT
Initial Bias
vs Temperature
INPUT
Voltage Range
UNITS
2 || 15
VISO = 240 Vrms 60Hz
VIN = 0V G = 0.5
VIN = 0V G = 50
0°C to +70°C G = 0.5
0°C to +70°C G = 50
VCC = 14V to 16V
vs Temperature
MAX
1
80
13
5
5
±1
±20
±20
±1
±20
±20
16
10
6
3
184
V
%
ppm/°C
ppm/kHr
%/V
mV
%
ppm/°C
ppm/kHr
%/V
V
mA
V
mA
mW
V
mA
SPECIFICATIONS
(CONT)
ELECTRICAL
At VCC = 15V, VDD = 5V, TA = +25°C, unless otherwise noted.
ISC300
PARAMETER
CONDITIONS
INPUT O/C SENSE
Sense Current
MIN
TYP
IS2, Sense 1 = 0V
–IS2, Sense 2 = 0V
REFERENCE CURRENT
Reference Current (IREF1)
Reference Currents Ratio
MAX
µA
µA
0.7
0.7
199
200
DIGITAL INPUTS A0, A1, G, CLK, RST (74HC EQUIVALENT)
High-Level Input Voltage
Low-Level Input Voltage
Input Rise and Fall Times (tR, tr)
CLK RST A0, A1, G
Pulse Width (tW)
CLK, RST
Setup (tSU)
Data Change to CLK High
Hold (tHO)
Data Change from CLK High
Release (tREG)
RST High to CLK High
µA
%
201
±0.5
IREF1 : IREF2
CLOCK SYNC CKI
Input Voltage - High Level
Input Voltage - Low Level
Input Current - High Level
Input Current - Low Level
Input Frequency
Input Duty Cycle
UNITS
3.5
V
V
ns
ns
ns
ns
ns
1.5
450
20
20
5
5
VCC = 15V
VCC = 15V
VIL = 11V VCC = 15V
VIL = 4V VCC = 15V
11
V
V
µA
µA
kHz
%
4
350
350
50
45
45
TEMPERATURE RANGE
Specification
Operating
Storage
θJA
TJ max
55
55
0
0
–40
°C
°C
°C
°C/W
°C
70
70
85
220
150
NOTES: (1) See “High Voltage Testing” Section. (2) IMR is defined with respect to the voltage between Com 1 and Com 2 with both inputs tied to Com 1. (3) CMR is
defined with respect to the input common, Com 1, only. (4) Deviation from a straight line between the end points of the output voltage. (5) Device output remains
monotonic. (6) Limit referred to VREF1.
PIN CONFIGURATION
ABSOLUTE MAXIMUM RATINGS
Signal Input Voltage ......................................................................... ±380V
Analog Supply Voltage VCC .................................................................. 18V
Digital Supply Voltage VDD ..................................................................... 7V
Voltage Across Barrier ................................................................. 800Vrms
Storage Temperature Range .......................................... –45°C to +100°C
Lead Temperature (soldering, 10s) ................................................ +300°C
Out Short Circuit Duration ........................................ Continuous to Com 2
Relative Humidity (non-condensing) ............................................. 95% RH
Bottom View
1
2
3
4
5
6
7
8
9
10
10V Ref
–VSS1
Sense 1
IREF1
+In
–In
IREF2
Sense 2
+VSS1
Com 1
NOTES: Stresses exceeding those listed above may cause permanent
damage to the device. Exposure to absolute maximum rating conditions for
extended periods may affect device reliability.
TIMING INFORMATION
18
19
20
21
22
23
24
25
26
27
28
tSU
VDD (+5V)
G
A0
A1
CLK
RST
DCom 2
VCC (+15V)
CKI
Com 2
Out
Data
tHO
tW
CLK
tW
tW
RST
t REL
®
3
ISC300
THEORY OF OPERATION
Sense Lines
The two sense lines can be configured to detect short or open
circuits e.g. transducer burn out. This would be indicated by
an out of range output (see Input Configuration in Applications section).
The ISC300 has no galvanic connection between the input
and output sections. The differential input signal is multiplied by the programmable gain amplifier and accurately
transferred across the isolation barrier to the output. The
output section demodulates the signal transferred from the
input section and transfers power to the input section.
Multiplexer
The multiplexer is used to route either the measurement
channel or the precision voltage references (used in system
calibration) to the programmable gain amplifier.
ISC300 DESIGN
The ISC300 consists of:
• A filtered differential high impedance input.
• Precision matched current sources.
• Fault detect bias resistors.
• Digitally selectable internal calibration references.
• Digitally selectable gain.
• Isolation of all digital and analog signals.
• Isolated DC/DC converter.
• Synchronizable internal oscillator.
• Two isolated power supplies available for external circuitry.
• Externally available 10V reference.
Isolation Barrier
The isolation barrier consists of two transformers and three
opto couplers. One transformer transmits the signal from the
input side to the output side. The other transmits power from
the output side to the input side. The opto-couplers are used
to isolate the logic used for mux select, gain and reference
voltage control.
Voltage Reference
INPUT SECTION
The voltage reference provides 10V, 0.1V and 0V references
for channel calibration. The 10V reference is also available
externally.
Filter
Since the ISC300 is designed to measure slowly changing
processes, the input filter is set for a cut off frequency of
2Hz. This gives good noise rejection at power frequencies of
50Hz and 60Hz.
Current References
Two matched 200µA current references are available for the
excitation of RTDs or for use in external signal conditioning
circuitry.
9
+VISO
2
–VISO
20M
8 Sense 2
5
Barrier
+VISO
Out
+IP
Filter
6
Channel 1 Out
PGA
Modulate
Demod
Rectify
Power
28
–IP
20M
3 Sense 1
–VISO
10.0V
Ref
1
4
7
99R
VREF
0.100V
IREF1
Current
Reference
IREF2
Com 1
Com1
Channel 4
A0
A1
O
P
T
O
Com 1
Input Side
Com 2
C
O
U
P
L
E
Output Side
FIGURE 1. ISC300 Block Diagram.
®
ISC300
CKI
26
Com 2
27
VDD (+5)
18
CLK
22
G
19
A0
20
A1
21
RST
23
DCom 2
24
Channel 3
R
–VISO
10
VCC (+15) 25
MUX
Channel 2
4
L
A
T
C
H
PGA
The programmable gain amplifier allows the user to digitally
select device gains of 0.5 and 50, allowing input ranges of
±0.1V or, ±10V full scale. When used in conjunction with
the 0.1V, 10V and common references, channel calibration
can be performed.
overvoltages below this level will not cause any damage.
The extinction voltage is above 500Vrms so that even
overvoltage-induced partial discharge will cease once the
barrier voltage is reduced to the rated level. Older high
voltage test methods relied on applying a large enough
overvoltage (above rating) to catastrophically break down
marginal parts, but not so high as to damage good ones. Our
new partial discharge testing gives us more confidence in
barrier reliability than breakdown/no breakdown criteria.
Isolated Supplies
Two 13V isolated supplies, capable of supplying 5mA each,
are available to power signal conditioning circuitry.
BASIC OPERATION
SIGNAL AND SUPPLY CONNECTIONS
As with any mixed signal analog and digital signal component, correct decoupling and signal routing precautions must
be observed to optimize performance. The ISC300 has an
internal 0.1µF decoupling capacitor at VCC, so additional
VCC decoupling will not be necessary. However, a ground
plane will minimize potential noise problems. If a low
impedance ground plane is not used, Com 2 should be tied
directly to the ground at the supply. It is not necessary to
connect DCom 2 and Com 2 at the device. Layout practices
associated with isolation signal conditioners are very important. The capacitance associated with the barrier and series
resistance in the signal and reference leads must be minimized. Any capacitance across the barrier will increase AC
leakage, and in conjunction with ground line resistance, may
degrade high frequency IMR, see Figure 2.
OUTPUT SECTION
The output section passes power across the isolation barrier
to provide the isolated supplies, and demodulates the signal
transmitted back across the isolation barrier.
ABOUT THE BARRIER
For any isolation product, barrier integrity is of paramount
importance in achieving high reliability. The ISC300 uses
miniature transformers designed to give maximum isolation
performance when encapsulated in a high dielectric strength
material. The device is designed so that the barrier is located
at the center of the package.
HIGH VOLTAGE TESTING
Burr-Brown Corporation has adopted a partial discharge test
criterion that conforms to the German VDE0884 Optocoupler Standards. This method requires the measurement of
minute current pulses (< 5pC) while applying 800Vrms,
60Hz high-voltage stress across every device isolation
barrier. During a two second test partial discharge must
occur five times on five separate half cycles of 60Hz,
and each time occurrence must not be separated by a line
period of more than four half cycles in order to produce a
partial discharge fail. This confirms transient overvoltage
(1.6 x Vrated) protection without damage. Life-test results
verify the absence of failure under continuous rated voltage
and maximum temperature.
INPUT CONFIGURATION
The ISC300 allows easy configuration for temperature measurement using an RTD. Figure 3 shows the basic connections for RTD operation. The two reference currents excite
the resistance transducer and a current-to-voltage conversion is made corresponding to the resistance value of the
transducer. If a gain of 50 is selected, a 10Ω resistance value
results in a (10 • 200µA) • 50 = 0.1V output; the 500Ω full
scale value gives a (500 • 200µA) • 50 = 5V output. The
connection of the sense line allows open circuit sensor
detection. An open circuit will give a corresponding > 5.1V
output. A short circuit will give a corresponding < 0.1V
output. See the Applications section under Fault Conditions
for more information.
This new test method represents the “state-of-the-art” for
nondestructive high voltage reliability testing. It is based on
the effects of non-uniform fields existing in heterogeneous
dielectric material during barrier degradation. In the case of
void non-uniformities, electric field stress begins to ionize
the void region before bridging the entire high voltage
barrier.
The transient conduction of charge during and after the
ionization can be detected externally as a burst of 0.01µs –
0.1µs current pulses that repeat on each AC voltage cycle.
The minimum AC barrier voltage that initiates partial discharge is defined as the “inception voltage.” Decreasing the
barrier voltage to a lower level is required before partial
discharge ceases and is defined as the “extinction voltage.”
CINT
Com 2
CEXT
Com 1
R
VISO
We have designed and characterized the package to yield an
inception voltage in excess of 800Vrms so that transient
FIGURE 2. Barrier Capacitance.
®
5
ISC300
ISOLATED SUPPLIES
The two isolated supplies available on the input side are
capable of supplying ±11.5V min at 5mA. These can be used
to provide power for external front-end circuitry for additional signal processing. When using the isolated supplies, it
is necessary to decouple them as close to the device as
possible. 10µF tantalum capacitors should be used. This will
also improve the signal-to-noise ratio.
Figure 4 shows the configuration for voltage measurement.
A full scale input range of ±10V can be accepted by the
ISC300. The two sense lines can be connected to give open
or short circuit detection. An open circuit will result in an
output of < –5.1V and a short circuit will give a < 0.1V
output. See the Applications section under Fault Conditions
for more information.
Figure 7 shows a possible circuit configuration using jumpers to select voltage or RTD operation.
Line Resistance
Com 1
Com 1
+In
0Ω
to
500 Ω
RS
– In
Filter and
MUX
Sense 2 20MΩ
IREF1
PGA
+VISO
IREF2
I1
I2
–VISO
FIGURE 3. Resistance Measurement Configuration.
Sense 1 20MΩ
–VISO
Line Resistance
+In
–10V
to
+10V
–In
Filter and
MUX
Sense 2 20MΩ
Com 1
FIGURE 4. Voltage Measurement Configuration.
®
ISC300
6
PGA
+VISO
MEASUREMENT CHANNEL
CALIBRATION
pins of each ISC300 in the system together (see Figure 6).
The ISC300 can also be synchronized by an external clock
driver.
The ISC300 is designed to allow easy system calibration
using its internal voltage reference. Programming pins A0,
A1 and G allows offset and full scale errors in gains of 0.5
and 50 to be measured.
1
0
50
1
1
+0.1V
0
1
No Change
1
+10V
1
0
Latch
1
^
Signal
1
1
RESET
0
X
CKI
CKI
CKI
CKI
CKI
CKI
N
No Change
ISC300
0
5
0.5
ISC300
0
4
CLK
0
ISC300
RST
Com 1
3
SELECT
AND GAIN
ISC300
G
2
GAIN
SELECT
ISC300
A0
1
A1
ISC300
INPUT
SELECT
Optional Clock Driver
FIGURE 6. Synchronizing Multi-ISC300 Applications.
System calibration would typically proceed as follows:
NOISE
Output noise is generated by the residual components of the
25kHz carrier that have not been removed from the signal.
This noise may be reduced by adding an output low pass
filter (see Figure 15 for an example of a 2 pole filter with
amplification, giving a ±10V output). The filter time constants should be set below the carrier frequency. The output
of the ISC300 is a switched capacitor and requires a high
impedance load to prevent degradation of linearity. Loads of
less than 1MΩ will cause an increase in noise at the carrier
frequency and will appear as ripple in the output waveform.
Lab Calibration
• Set ISC300 gain.
• Set input to 0V reference, measure Offset.
• Connect external precision V reference, measure Gain.
• Remove external V reference and set input to 10V or
0.1V reference.
Offset and Gain are now calibrated to an external precision reference—record the numbers.
Field Calibration
• Set ISC300 gain.
• Set input to 0V reference, measure Offset.
• Set input to 10V or 0.1V, measure Gain.
• Recalibrate system.
APPLICATIONS
This section describes the design criteria of various applications of the ISC300.
SYNCHRONIZATION
As the internal modulation frequencies of several ISC300s
can be marginally different, ‘beat’ frequencies ranging from
a few Hz to a few kHz can exist in multi ISC300 applications. The internal clock (see Figure 5) starts when power is
applied and runs at typically 50kHz. The ISC300 design
accommodates ‘internal synchronous’ noise which is caused
by minute timing differences, but synchronous beat frequency noise will not be strongly attenuated, especially at
low frequencies if it is introduced via the power, signal or
ground paths. To overcome this problem, the design allows
the synchronization of each oscillator in the system to one
frequency. This is done by connecting the CKI (clock in)
2, 3 AND 4 WIRE RESISTANCE MEASUREMENTS
Two wire resistance measurements are prone to errors due to
lead resistances. The voltage error can be significant since
the voltmeter measures on the lines supplying the RTD
Sense 1
2
J1
1
20MΩ
–VISO
IREF1
–VISO
3
+In
+In
–In
–In
1
J2
3
Filter and
MUX
PGA
IREF2
–VISO
2
Sense 2
220pF
Com 1
Com
CKI
f = 50kHz
39k Ω
Simplified Schematic
FIGURE 5. CKI Input.
+VISO
20MΩ
Com 1
Jumper
Mode
Voltage
J1
J2
1-2
1-2
RTD
2-3
2-3
FIGURE 7. Mode Selection Jumpers.
®
7
ISC300
excitation current. Four wire measurements avoid this problem by measuring the voltage generated across the RTD on
a second pair of wires. Very little current flows through the
voltmeter, therefore the lead resistance error contribution is
negligible. Three wire resistance measurements also avoid
lead length resistance errors.
Com 1
+In
RS
0V
In Figure 8:
–In
(+In) = –r1 (I1 + I2) – r2I1
(1)
(2)
(–In) = –r1 (I1 + I2) – R2I2 – r3I2
(1) – (2)
I1
I2
= –r2I2 + RSI2 + r3I2
Since r1 = r2 = r3
(LEADS)
and I1 = I2
Output < +0.1V
–VISO
VIN = RS I2
FIGURE 10. RS Short Circuit.
FAULT CONDITIONS
The ISC300 can be configured to detect line or transducer
faults which may occur in a system. Figures 8 to 14 show
how the output of the ISC300 will reflect these various fault
conditions by giving corresponding out of range outputs.
Com 1
+In
RS
–VISO
T1
–In
Com 1
I1
I 1 + I2
I2
T2
+In
RS
I2 • RS = VIN
T3
Output < –5.1V
–VISO
–In
I1
FIGURE 11. +In Open Circuit.
I2
Com 1
Output = G • VIN
–VISO
FIGURE 8. Normal Operation.
+In
RS
+VISO
–In
Com 1
I1
I2
+In
RS
+VISO
Output > +5.1V
–In
I1
Output > +5.1V
FIGURE 12. –In Open Circuit.
I2
–VISO
FIGURE 9. RS Open Circuit.
®
ISC300
8
–VISO
RS
Com 1
Com 1
+In
+In
RS
Undefined
Undefined
–In
–In
I1
Output Undefined
I1
I2
I2
Output Undefined
–VISO
–VISO
FIGURE 13. –In and +In Open Circuit.
FIGURE 14. Com 1 Open Circuit.
APPLICATIONS FLEXIBILITY
excite the measurement bridge and the INA102 is used to
amplify the bridge delta voltage. Connecting pins 4 and 7
together, and pins 5 and 6 together on the INA102 sets its
gain to 1000.
ISOLATED VOLTAGE MEASUREMENT CHANNEL
Figure 15 shows the ISC300 configured for a ±10V input.
With a few external components the ISC300 can accurately
convert a ±10V input to an isolated ±10V output with no
external adjustments. The primary function of the output
circuitry is to add gain to convert the ±5V output of the
ISC300 to ±10V, and to reduce output impedance. The
addition of a few resistors and capacitors provides an active
low pass filter with a cut off frequency of typically 200Hz.
The filter response is flat to 1dB and rolls off from cut off
at –12dB per octave.
ISOLATED 4 TO 20MA RECEIVER
In Figure 17, the ISC300 converts a 4 to 20mA current to an
isolated 0 to 5V output. The 6.25Ω resistor converts the 4 to
20mA input to 0.025 to 0.125V. The 125Ω resistor in
conjunction with the 200µA current source provides an
offset of –0.025V. Fine offset and gain adjustment gives an
accurate 0 to 0.1V input range.
Offset and Gain Adjustment
• Adjust R1 for 5V change on the output corresponding to
16mA change on the input.
ISOLATED MEASUREMENT BRIDGE CIRCUIT
Figure 16 shows a measurement bridge circuit using the
ISC300. All the input circuitry is powered by the ISC300
isolated supplies. The OPA1013 dual op amp is used to
• Adjust R2 with 4mA input for 0V output.
6.8nF
+VCC
Sense 1
100kΩ
+In
100kΩ
Out
6.8nF
ACom 2
+10VIN
±10VOUT
OPA27GP
22kΩ
+VDD
–In
22kΩ
ƒ–3dB = 200Hz
Sense 2
Logic
Control
Com 1
DCom 2
FIGURE 15. Isolated Voltage Measurement Channel with Output Filter.
®
9
ISC300
+VCC
1/2 OPA1013
+VSS1 –VSS1
+VSS1
20kΩ
VREF1
B
Out
10k Ω
–VSS1
ACom 2
+VSS1
+VDD
+In
INA102
–In
1kΩ
Logic
Control
1kΩ
–VSS1
100kΩ
Com 1
1kΩ
DCom 2
1kΩ
100kΩ
+VSS1
A
–VSS1
1/2 OPA1013
FIGURE 16. Isolated Instrument Bridge System.
+VCC
R1
+In
Out
0 to 5V
125Ω
20Ω
4 to 20mA
6.25Ω
ACom 2
10Ω
100Ω
220Ω
R2
10Ω
330Ω
+VDD
–In
IREF1
+VDD
Com 1
FIGURE 17. Isolated 4 to 20mA receiver (0 to 5V output).
®
ISC300
10
DCom 2
+VCC
+VSS1 –VSS1
IREF2
Out
ACom 2
+VSS1
+VDD
+In
INA102
–In
–VSS1
Logic
Control
IREF1
Com 1
DCom 2
FIGURE 18. Temperature Measurement Using Thermocouple with Small Span.
+VCC
+VSS1 –VSS1
IREF2
Out
ACom 2
+VSS1
+VDD
+In
INA102
–In
4990Ω
30Ω
100Ω
–VSS1
Logic
Control
IREF1
Com 1
DCom 2
FIGURE 19. Thermocouple with Cold Junction Compensation.
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.
®
11
ISC300