Burr-Brown ISO175 Instrumentation amplifier Datasheet

ISO165
ISO175
®
ISO
165
ISO
175
Precision, Isolated
INSTRUMENTATION AMPLIFIER
FEATURES
DESCRIPTION
● RATED
1500Vrms Continuous
2500Vrms for One Minute
100% TESTED FOR PARTIAL DISCHARGE
ISO165 and ISO175 are precision isolated instrumentation amplifiers incorporating a novel duty cycle
modulation-demodulation technique and excellent accuracy. A single external resistor sets the gain. Internal
input protection can withstand up to ±40V without
damage. The signal is transmitted digitally across a
differential capacitive barrier. With digital modulation
the barrier characteristics do not affect signal integrity.
This results in excellent reliability and good high
frequency transient immunity across the barrier. Both
the amplifier and barrier capacitors are housed in a
plastic DIP. ISO165 and ISO175 differ in frequency
response and linearity.
● HIGH IMR: 115dB at 50Hz
● LOW NONLINEARITY: ±0.01%
● LOW INPUT BIAS CURRENT: 10nA max
● LOW INPUT OFFSET VOLTAGE: 101mV max
● INPUTS PROTECTED TO ±40V
● BIPOLAR OPERATION: VO = ±10V
● SYNCHRONIZATION CAPABILITY
● 24-PIN PLASTIC DIP: 0.3" Wide
These amplifiers are easy to use. A power supply
range of ±4.5V to ±18V makes these amplifiers ideal
for a wide range of applications.
APPLICATIONS
● INDUSTRIAL PROCESS CONTROL
Transducer Isolator, Thermocouple
Isolator, RTD Isolator, Pressure Bridge
Isolator, Flow Meter Isolator
● POWER MONITORING
● MEDICAL INSTRUMENTATION
● ANALYTICAL MEASUREMENTS
● BIOMEDICAL MEASUREMENTS
● DATA ACQUISITION
● TEST EQUIPMENT
● POWER MONITORING
● GROUND LOOP ELIMINATION
5
Shield 1
1
VIN–
22
FBP
21
Ext Osc
4
+VS1
15
+VS2
Shield 2
VOUT
2
FBN
24
VIN+
Com2
Com1
23
GND1
–VS1
20
3
–VS2
13
GND2
12
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
©
1996 Burr-Brown Corporation
PDS-1293
Printed in U.S.A. May, 1996
14
11
10
SPECIFICATIONS
At TA = +25°C, VS1 = VS2 = ±15V, and RL = 2kΩ unless otherwise noted.
ISO165P
PARAMETER
ISOLATION(1)
Voltage Rated Continuous:
AC
DC
100% Test (AC, 50Hz)
Isolation-Mode Rejection
AC 50Hz
DC
Barrier Impedance
Leakage Current
CONDITIONS
MIN
TMIN to TMAX
TMIN to TMAX
1s; Partial Discharge ≤ 5pC
1500
2121
2500
1500Vrms
TYP
MAX
VISO = 240Vrms, 50Hz
MIN
Gain vs Temperature
Nonlinearity
INPUT OFFSET VOLTAGE
Initial Offset
G=1
G = 10
G = 100
G=1
G=1
G = 10
G = 100
1
vs Supply
±10
±40
±40
OUTPUT
Voltage Range
Current Drive
Capacitive Load Drive
Ripple Voltage
FREQUENCY RESPONSE
Small Signal Bandwidth
Slew Rate
POWER SUPPLIES
Rated Voltage
Voltage Range
Quiescent Current
VS1
VS2
TEMPERATURE RANGE
Operating
Storage
±10
±10
±40
±10
±40
®
2
mV
mV/V
±10
±10
V
nA
pA/°C
nA
pA/°C
0.1
10
0.1
10
V
mA
µF
mVp-p
6
6
6
0.9
60
60
50
0.9
kHz
kHz
kHz
V/µs
15
±18
±4.5
±7.4
±7.5
–40
–40
%
%
%
ppm/°C
%
%
%
µV/°C
±10
±5
15
±4.5
NOTE: (1) All devices receive a 1s test. Failure criterion is ≥ 5 pulses of ≥ 5pc.
ISO165/ISO175
520 

± 1 +


G 
±2
±10
±5
G=1
G = 10
G = 100
VO = ±10V, G = 10
±0.104
101

±  0.125 +


G 
170 

± 1 +


G 
±2
G=1
INPUT
Voltage Range
Bias Current
vs Temperature
Offset Current
vs Temperature
±0.054
51

±  0.125 +


G
G = 1, 100
±0.102
±0.04
dB
dB
Ω || pF
µArms
V/V
±0.95
±11
±0.052
±0.01
1
±0.35
±0.07
±0.95
±11
UNITS
Vrms
VDC
Vrms
 50k 
1+ 

 RG 
±0.35
±0.07
vs Temperature
MAX
115
160
1014 || 6
0.8
 50k 
1+ 

 RG 
Gain Error
TYP
1500
2121
2500
115
160
1014 || 6
0.8
GAIN
ISO175P
85
125
–40
–40
±18
V
V
±7.4
±7.5
mA
mA
85
125
°C
°C
ABSOLUTE MAXIMUM RATINGS
PIN CONFIGURATION
Supply Voltage ................................................................................... ±18V
Analog Input Voltage Range .............................................................. ±40V
External Oscillator Input ..................................................................... ±25V
Com 1 to GND1 ................................................................................... ±1V
Com 2 to GND2 ................................................................................... ±1V
Continuous Isolation Voltage: .................................................... 1500Vrms
IMV, dv/dt ...................................................................................... 20kV/µs
Junction Temperature ...................................................................... 150°C
Storage Temperature ...................................................... –40°C to +125°C
Lead Temperature (soldering, 10s) ................................................ +300°C
Output Short Duration .......................................... Continuous to Common
ELECTROSTATIC
DISCHARGE SENSITIVITY
VIN–
1
24 VIN+
FBN
2
23 Com 1
VS1–
3
22 FBP
VS1+
4
21 EXT OSC
Shield 1
5
20 GND 1
Com 2 10
15 VS2+
14 Shield 2
VOUT 11
Any integrated circuit can be damaged by ESD. Burr-Brown
recommends that all integrated circuits be handled with
appropriate precautions. Failure to observe proper handling
and installation procedures can cause damage.
GND 2 12
ESD damage can range from subtle performance degradation 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.
13 VS2–
PACKAGE INFORMATION
MODEL
PACKAGE
PACKAGE DRAWING
NUMBER(1)
ISO165P
ISO175P
24-Pin Plastic DIP
24-Pin Plastic DIP
243-2
243-2
NOTE: (1) For detailed drawing and dimension table, please see end of data
sheet, or Appendix D of Burr-Brown IC Data Book.
ORDERING INFORMATION
MODEL
PACKAGE
BANDWIDTH
ISO165P
ISO175P
24-Pin Plastic DIP
24-Pin Plastic DIP
6kHz
60kHz
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.
®
3
ISO165/ISO175
TYPICAL PERFORMANCE CURVES
At TA = +25°C, VS1 = VS2 = ±15V, and RL = 2kΩ unless otherwise noted.
ISOLATION MODE VOLTAGE
vs FREQUENCY
PSRR vs FREQUENCY
60
54
2k
Max AC
Rating
1k
40
PSRR (dB)
Peak Isolation Voltage
Max DC Rating
Degraded
Performance
100
+VS1, +VS2
–VS1, –VS2
20
Typical
Performance
10
0
100
10k
1k
100k
1M
10M
100M
1
10
Frequency (Hz)
10k
1k
100k
1M
Frequency (Hz)
ISOLATION LEAKAGE CURRENT
vs FREQUENCY
IMR vs FREQUENCY
100mA
160
10mA
140
1mA
IMR (dB)
120
1500 Vrms
100µA
10µA
100
80
240 Vrms
1µA
60
0.1µA
40
10
1
100
1k
10k
100k
1M
1
10
100
1k
10k
Frequency (Hz)
Frequency (Hz)
SIGNAL RESPONSE vs CARRIER FREQUENCY
SINE RESPONSE ISO175
(f = 2kHz, Gain = 10)
100k
1M
15
10
Output Voltage (V)
0
VOUT/VIN (dB)
Leakage Current (rms)
100
–20dB/dec (for comparison only)
–20
5
0
–5
–10
–40
–15
fIN (Hz)
0
fC
2fC
0
3fC
200
400
600
Time (µs)
fOUT (Hz) 0
fc /2
0
fC /2
0
fC /2
0
®
ISO165/ISO175
4
800
1000
TYPICAL PERFORMANCE CURVES (CONT)
At TA = +25°C, VS1 = VS2 = ±15V, and RL = 2kΩ unless otherwise noted.
SINE RESPONSE ISO175
(f = 20kHz, Gain = 10)
STEP RESPONSE ISO175
15
10
5
0
5
–5
–10
0
Output Voltage (V)
Output Voltage (V)
10
–5
–10
–15
10
5
0
–5
–10
–15
0
200
400
600
800
1000
0
100
200
Time (µs)
400
500
GAIN vs FREQUENCY ISO175
80
5
0
–5
–10
10
5
60
Gain (dB)
10
Input Voltage (V)
15
Output Voltage (V)
300
Time (µs)
STEP RESPONSE ISO175
G = 1000
G = 100
40
G = 10
20
0
G=1
0
–5
–10
–20
–15
15
20
40
60
80
1k
100
INPUT COMMON-MODE RANGE
vs OUTPUT VOLTAGE
INPUT BIAS AND OFFSET CURRENT
vs TEMPERATURE
G ≥ 10
5
G ≥ 10
G=1
G=1
5
VD/2
0
VD/2
–5
–15
–15
100k
Frequency (Hz)
10
–10
10k
Time (µs)
Input Bias and Offset Current (nA)
0
Common-Mode Voltage (V)
Input Voltage (V)
15
–
VO
+
–
+
VCM
All
Gains
All
Gains
4
IOS
3
2
±Ib
1
0
–1
–2
–3
–4
–5
–10
–5
0
5
10
15
–75
Output Voltage (V)
–50
–25
0
25
50
75
100
125
Temperature (°C)
®
5
ISO165/ISO175
BASIC OPERATION
ISO165 and ISO175 instrumentation input isolation amplifiers are comprised of a precision instrumentation amplifier
followed by an isolation amplifier. The input and output
isolation sections are galvanically isolated and EMI shielded
by matched capacitors.
gain equation (1). Low resistor values required for high
gain can make wiring resistance important. Sockets add to
the wiring resistance which will contribute additional gain
error (possibly an unstable gain error) in gains of approximately 100 or greater.
Signal and Power Connections
Figure 1 shows power and signal connections. Each power
supply pin should be bypassed with a 1µF tantalum capacitor located as close to the amplifier as possible. All ground
connections should be run independently to a common point
if possible. Signal Common on both input and output sections provide a high-impedance point for sensing signal
ground in noisy applications. Com 1 and Com 2 must have
a path to ground for bias current return and should be
maintained within ±1V of GND1 and GND2, respectively.
INPUT COMMON-MODE RANGE
The linear voltage range of the input circuitry of the ISO165
and ISO175 are from approximately 2.5V below the positive
supply voltage to 2.5V above the negative supply. As a
differential input voltage causes the output voltage to increase, however, the linear input range will be limited by the
output voltage swing of the internal amplifiers. Thus, the
linear common-mode input range is related to the output
voltage of the complete input amplifier.
This behavior also depends on the supply voltage—see
performance curves “Input Common-Mode Range vs Output Voltage.”
SETTING THE GAIN
Gain of the ISO165 and ISO175 is set by connecting a single
external resistor RG, connected between pins 2 and 22.
G = 1+
50kΩ
RG
Input-overload can produce an output voltage that appears
normal. For example, if an input overload condition drives
both input amplifiers to their positive output swing limit, the
difference voltage measured by the output amplifier will be
near zero. The output of the ISO165 and ISO175 will be near
0V even though both inputs are overloaded.
(1)
Commonly used gains and resistor values are shown in
Figure 1.
The 50kΩ term in equation (1) comes from the sum of the
two internal feedback resistors. These on-chip metal film
resistors are laser trimmed to accurate absolute values. The
accuracy and temperature coefficient of these resistors are
included in the gain accuracy and drift specifications of the
ISO165 and ISO175.
INPUT PROTECTION
The inputs of the ISO165 and ISO175 are individually
protected for voltages up to ±40V referenced to GND1. For
example, a condition of –40V on one input and +40V on the
other input will not cause damage. Internal circuitry on each
input provides low series impedance under normal signal
conditions. To provide equivalent protection, series input
resistors would contribute excessive noise. If the input is
The stability and temperature drift of the external gain
setting resistor RG, also affects gain. RG’s contribution to
gain accuracy and drift can be directly inferred from the
0.1µF
+
1µF
+
1µF
0.1µF
+VS1
+VS2
5
Shield 1
DESIRED
GAIN
1
2
8
10
20
50
100
200
500
1000
2000
6000
10000
NEAREST 1% RG
(Ω)
RG
(Ω)
NC(1)
50.00k
12.50k
5.556k
2.632k
1.02k
505.1
251.2
100.2
50.05
25.01
10.00
5.001
NC(1)
49.9k
12.4k
5.62k
2.61k
1.02k
511
249
100
49.9
24.9
10
4.99
21
Ext Osc
4
+VS1
15
+VS2
1 VIN+
VIN–
Shield 2
22 FBP
14
VOUT 11
RG
VIN+
Com2
24 VIN+
Com 1
23
–VS1
NOTE: (1) No Connection.
0.1µF
GND 1
–VS1
20
3
+
FIGURE 1. Basic Connections.
®
ISO165/ISO175
VOUT
2 FBN
6
–VS2
RLOAD
GND 2
13
1µF
10
12
+
1µF
–VS2
0.1µF
overloaded, the protection circuitry limits the input current
to a safe value of approximately 1.5 to 5mA. The inputs are
protected even if the power supplies are disconnected or
turned off.
more complex. The “Signal Response vs Carrier Frequency”
performance curve describes this behavior graphically. The
upper curve illustrates the response for input signals varying
from DC to fC/2. At input frequencies at or above fC/2, the
device generates an output signal component that varies in
both amplitude and frequency, as shown by the lower curve.
The lower horizontal scale shows the periodic variation in
the frequency of the output component. Note that at the
carrier frequency and its harmonics, both the frequency and
amplitude of the response go to zero. These characteristics
can be exploited in certain applications.
SYNCHRONIZED OPERATION
ISO165 and ISO175 can be synchronized to an external
signal source. This capability is useful in eliminating troublesome beat frequencies in multichannel systems and in rejecting AC signals and their harmonics. To use this feature, an
external signal must be applied to the Ext Osc pin. ISO165
can be synchronized over the 100kHz to 200kHz range and
ISO175 can be synchronized over the 400kHz to 700kHz
range.
It should be noted that for the ISO175, the carrier frequency
is nominally 500kHz and the –3dB point of the amplifier is
60kHz. Spurious signals at the output are not significant
under these circumstances unless the input signal contains
significant components above 250kHz.
The ideal external clock signal for the ISO165 and ISO175
is a ±4V sine wave or ±4V, 50% duty-cycle triangle wave.
The Ext Osc pin of the ISO165 and ISO175 can be driven
directly with a ±3V to ±5V sine or 25% to 75% duty-cycle
triangle wave and the ISO amp’s internal modulator/demodulator circuitry will synchronize to the signal.
For the ISO165, the carrier frequency is nominally 110kHz
and the –3dB point of the amplifier is 6kHz.
When periodic noise from external sources such as system
clocks and DC/DC converters are a problem, ISO165 and
ISO175 can be used to reject this noise. The amplifier can
be synchronized to an external frequency source, fEXT,
placing the amplifier response curve at one of the frequency and amplitude nulls indicated in the “Signal Response vs Carrier Frequency” performance curve. Figure 3
shows circuitry with opto-isolation suitable for driving the
Ext Osc input from TTL levels.
ISO175 can also be synchronized to a 400kHz to 700kHz
Square-Wave External Clock since an internal clamp and
filter provide signal conditioning. A square-wave signal of
25% to 75% duty cycle, and ±3V to ±20V level can be used
to directly drive the ISO175.
With the addition of the signal conditioning circuit shown in
Figure 2, any 10% to 90% duty-cycle square-wave signal
can be used to drive the ISO165 and ISO175 Ext Osc pin.
With the values shown, the circuit can be driven by a
4Vp-p TTL signal. For a higher or lower voltage input,
increase or decrease the 1kΩ resistor, RX, proportionally,
e.g. for a ±4V square-wave (8Vp-p) RX should be increased
to 2kΩ. The value of CX used in the Figure 2 circuit depends
on the frequency of the external clock signal. CX should be
30pF for ISO175 and 680pF for ISO165.
+5V
+15V
200Ω
2.5kΩ
2
C2
8
Ext Osc on
ISO165/ISO175
(Pin 21)
2.5kΩ
6
C1
10kΩ
fIN
1µF
Sq Wave In
RX
1kΩ
10kΩ
TTL
5
3
6N136
CX
C1 =
(
140E-6
fIN
)
– 350pF
C2 = 10 X C1, with a minimum 10nF
OPA602
Triangle Out
to ISO165/175
Ext Osc
FIGURE 3. Synchronization with Isolated Drive Circuit for
Ext Osc Pin.
FIGURE 2. Square-Wave to Triangle Wave Signal Conditioner for Driving ISO165/175 Ext Osc Pin.
ISOLATION MODE VOLTAGE
Isolation Mode Voltage (IMV) is the voltage appearing
between isolated grounds GND1 and GND2. The IMV can
induce errors at the output as indicated by the plots of IMV
versus Frequency. It should be noted that if the IMV frequency exceeds fC/2, the output will display spurious outputs in a manner similar to that described above, and the
amplifier response will be identical to that shown in the
CARRIER FREQUENCY CONSIDERATIONS
ISO165 and ISO175 amplifiers transmit the signal across the
ISO-barrier by a duty-cycle modulation technique. This
system works like any linear amplifier for input signals
having frequencies below one half the carrier frequency, fC.
For signal frequencies above fC/2, the behavior becomes
®
7
ISO165/ISO175
“Signal Response vs Carrier Frequency” performance curve.
This occurs because IMV-induced errors behave like inputreferred error signals. To predict the total IMR, divide the
isolation voltage by the IMR shown in “IMR vs Frequency”
performance curve and compute the amplifier response to
this input-referred error signal from the data given in the
“Signal Response vs Carrier Frequency” performance curve.
Due to effects of very high-frequency signals, typical IMV
performance can be achieved only when dV/dT of the
isolation mode voltage falls below 1000V/µs. For convenience, this is plotted in the typical performance curves
for the ISO165 and ISO175 as a function of voltage and
frequency for sinusoidal voltages. When dV/dT exceeds
1000V/µs but falls below 20kV/µs, performance may be
degraded. At rates of change above 20kV/µs, the amplifier
may be damaged, but the barrier retains its full integrity.
Lowering the power supply voltages below ±15V may
decrease the dV/dT to 500V/µs for typical performance, but
the maximum dV/dT of 20kV/µs remains unchanged.
phenomenon is that, if the discharge does not occur, the
insulation system retains its integrity. If the discharge begins, and is allowed to continue, the action of the ions and
electrons within the defect will eventually degrade any
organic insulation system in which they occur. The measurement of partial discharge is still useful in rating the devices
and providing quality control of the manufacturing process.
The inception voltage for these voids tends to be constant, so
that the measurement of total charge being redistributed
within the dielectric is a very good indicator of the size of the
voids and their likelihood of becoming an incipient failure.
The bulk inception voltage, on the other hand, varies with
the insulation system, and the number of ionization defects
and directly establishes the absolute maximum voltage (transient) that can be applied across the test device before
destructive partial discharge can begin. Measuring the bulk
extinction voltage provides a lower, more conservative voltage from which to derive a safe continuous rating. In
production, measuring at a level somewhat below the expected inception voltage and then derating by a factor
related to expectations about system transients is an accepted practice.
Leakage current is determined solely by the impedance of
the barrier capacitance and is plotted in the “Isolation Leakage Current vs Frequency” curve.
PARTIAL DISCHARGE TESTING
Not only does this test method provide far more qualitative
information about stress-withstand levels than did previous
stress tests, but it provides quantitative measurements from
which quality assurance and control measures can be based.
Tests similar to this test have been used by some manufacturers, such as those of high-voltage power distribution
equipment, for some time, but they employed a simple
measurement of RF noise to detect ionization. This method
was not quantitative with regard to energy of the discharge,
and was not sensitive enough for small components such as
isolation amplifiers. Now, however, manufacturers of HV
test equipment have developed means to quantify partial
discharge. VDE in Germany, an acknowledged leader in
high-voltage test standards, has developed a standard test
method to apply this powerful technique. Use of partial
discharge testing is an improved method for measuring the
integrity of an isolation barrier.
ISOLATION VOLTAGE RATINGS
Because a long-term test is impractical in a manufacturing
situation, the generally accepted practice is to perform a
production test at a higher voltage for some shorter time.
The relationship between actual test voltage and the continuous derated maximum specification is an important one.
Historically, Burr-Brown has chosen a deliberately conservative one: VTEST = (2 x ACrms continuous rating) +
1000V for 10 seconds, followed by a test at rated ACrms
voltage for one minute. This choice was appropriate for
conditions where system transients are not well defined.
Recent improvements in high-voltage stress testing have
produced a more meaningful test for determining maximum
permissible voltage ratings, and Burr-Brown has chosen to
apply this new technology in the manufacture and testing of
the ISO165 and ISO175.
PARTIAL DISCHARGE
When an insulation defect such as a void occurs within an
insulation system, the defect will display localized corona or
ionization during exposure to high-voltage stress. This ionization requires a higher applied voltage to start the
discharge and lower voltage to maintain it or extinguish it
once started. The higher start voltage is known as the
inception voltage, while the extinction voltage is that level
of voltage stress at which the discharge ceases. Just as the
total insulation system has an inception voltage, so do the
individual voids. A voltage will build up across a void until
its inception voltage is reached, at which point the void will
ionize, effectively shorting itself out. This action redistributes electrical charge within the dielectric and is known as
partial discharge. If, as is the case with AC, the applied
voltage gradient across the device continues to rise, another
partial discharge cycle begins. The importance of this
To accommodate poorly-defined transients, the part under
test is exposed to voltage that is 1.6 times the continuousrated voltage and must display less than or equal to 5pC
partial discharge level in a 100% production test.
APPLICATIONS
The ISO165 and ISO175 isolation amplifiers are used in
three categories of applications:
• Accurate isolation of signals from high voltage ground
potentials,
• Accurate isolation of signals from severe ground noise and,
• Fault protection from high voltages in analog measurements.
®
ISO165/ISO175
8
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