AC1059 [ADI]
Precision, Wide Bandwidth 3-Port Isolation Amplifier; 精密，宽带三端口隔离放大器
| 型号： | AC1059 |
| 厂家： | 
ADI |
| 描述： | Precision, Wide Bandwidth 3-Port Isolation Amplifier |
| 文件： | 总8页 (文件大小：301K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
Precision, Wide Bandwidth
3-Port Isolation Amplifier
a
AD210
FUNCTIONAL BLOCK DIAGRAM
FEATURES
High CMV Isolation: 2500 V rms Continuous
؎3500 V Peak Continuous
INPUT
MOD
OUTPUT
16
FB
T1
Small Size: 1.00"
؋
2.10" ؋
0.350" Three-Port Isolation: Input, Output, and Power
Low Nonlinearity: ؎0.012% max
Wide Bandwidth: 20 kHz Full-Power (–3 dB)
Low Gain Drift: ؎25 ppm/؇C max
High CMR: 120 dB (G = 100 V/V)
Isolated Power: ؎15 V @ ؎5 mA
Uncommitted Input Amplifier
–IN 17
1
2
DEMOD
FILTER
V
O
19
+IN
I
O
18
COM
COM
T3
POWER
POWER
T2
+V
–V
+V
–V
3
4
14
15
ISS
OSS
OUTPUT
POWER
SUPPLY
INPUT
POWER
SUPPLY
ISS
OSS
OSCILLATOR
AD210
APPLICATIONS
30
29
Multichannel Data Acquisition
High Voltage Instrumentation Amplifier
Current Shunt Measurements
Process Signal Isolation
PWR
PWR COM
GENERAL DESCRIPTION
mode voltage isolation between any two ports. Low input
The AD210 is the latest member of a new generation of low
cost, high performance isolation amplifiers. This three-port,
wide bandwidth isolation amplifier is manufactured with sur-
face-mounted components in an automated assembly process.
The AD210 combines design expertise with state-of-the-art
manufacturing technology to produce an extremely compact
and economical isolator whose performance and abundant user
features far exceed those offered in more expensive devices.
capacitance of 5 pF results in a 120 dB CMR at a gain of 100,
and a low leakage current (2 µA rms max @ 240 V rms, 60 Hz).
High Accuracy: With maximum nonlinearity of ±0.012% (B
Grade), gain drift of ±25 ppm/°C max and input offset drift of
(±10 ±30/G) µV/°C, the AD210 assures signal integrity while
providing high level isolation.
Wide Bandwidth: The AD210’s full-power bandwidth of
20 kHz makes it useful for wideband signals. It is also effective
in applications like control loops, where limited bandwidth
could result in instability.
The AD210 provides a complete isolation function with both
signal and power isolation supplied via transformer coupling in-
ternal to the module. The AD210’s functionally complete de-
sign, powered by a single +15 V supply, eliminates the need for
an external DC/DC converter, unlike optically coupled isolation
devices. The true three-port design structure permits the
AD210 to be applied as an input or output isolator, in single or
multichannel applications. The AD210 will maintain its high
performance under sustained common-mode stress.
Small Size: The AD210 provides a complete isolation function
in a small DIP package just 1.00" × 2.10" × 0.350". The low
profile DIP package allows application in 0.5" card racks and
assemblies. The pinout is optimized to facilitate board layout
while maintaining isolation spacing between ports.
Three-Port Design: The AD210’s three-port design structure
allows each port (Input, Output, and Power) to remain inde-
pendent. This three-port design permits the AD210 to be used
as an input or output isolator. It also provides additional system
protection should a fault occur in the power source.
Providing high accuracy and complete galvanic isolation, the
AD210 interrupts ground loops and leakage paths, and rejects
common-mode voltage and noise that may other vise degrade
measurement accuracy. In addition, the AD210 provides pro-
tection from fault conditions that may cause damage to other
sections of a measurement system.
Isolated Power: ±15 V @ 5 mA is available at the input and
output sections of the isolator. This feature permits the AD210
to excite floating signal conditioners, front-end amplifiers and
remote transducers at the input as well as other circuitry at the
output.
PRODUCT HIGHLIGHTS
The AD210 is a full-featured isolator providing numerous user
benefits including:
Flexible Input: An uncommitted operational amplifier is pro-
vided at the input. This amplifier provides buffering and gain as
required and facilitates many alternative input functions as
required by the user.
High Common-Mode Performance: The AD210 provides
2500 V rms (Continuous) and± 3500 V peak (Continuous) common-
REV. A
Information furnished by Analog Devices is believed to be accurate and
reliable. However, no responsibility is assumed by Analog Devices for its
use, nor for any infringements of patents or other rights of third parties
which may result from its use. No license is granted by implication or
otherwise under any patent or patent rights of Analog Devices.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 617/329-4700
Fax: 617/326-8703
AD210–SPECIFICATIONS
(typical @ +25؇C, and VS = +15 V unless otherwise noted)
OUTLINE DIMENSIONS
Model
AD210AN
AD210BN
AD210JN
Dimensions shown in inches and (mm).
GAIN
Range
Error
1 V/V – 100 V/V
±2% max
+25 ppm/°C max
±50 ppm/°C max
±0.002%/V
*
*
*
*
*
*
*
±1% max
*
*
*
vs. Temperature(0°C to +70°C)
(–25°C to +85°C)
vs. Supply Voltage
Nonlinearity1
±0.025% max
±0.012% max
INPUT VOLTAGE RATINGS
Linear Differential Range
Maximum Safe Differential Input
Max. CMV Input-to-Output
ac, 60 Hz, Continuous
±10 V
±15 V
*
2500 V rms
±3500 V peak
*
*
*
*
*
*
1500 V rms
±2000 V peak
dc, Continuous
Common-Mode Rejection
*
60 Hz, G = 100 V/V
*
R
S ≤ 500 Ω Impedance Imbalance
120 dB
*
2 µA rms max
*
*
*
*
Leakage Current Input-to-Output
@ 240 V rms, 60 Hz
INPUT IMPEDANCE
Differential
Common Mode
l012
5 GΩʈ5 pF
Ω
*
*
*
*
AC1059 MATING SOCKET
INPUT BIAS CURRENT
Initial, @ +25°C
vs. Temperature (0°C to +70°C)
30 pA typ (400 pA max)
10 nA max
*
*
*
*
*
*
(–25°C to +85°C) 30 nA max
INPUT DIFFERENCE CURRENT
Initial, @ +25°C
vs. Temperature(0°C to + 70°C)
(–25°C to +85°C)
5 pA typ (200 pA max)
2 nA max
10 nA max
*
*
*
*
*
*
INPUT NOISE
Voltage (l kHz)
(10 Hz to 10 kHz)
Current (1 kHz)
18 nV/√Hz
4 µV rms
0.01 pA/√Hz
*
*
*
*
*
*
FREQUENCY RESPONSE
Bandwidth (–3 dB)
G = 1 V/V
G = 100 V/V
Settling Time (±10 mV, 20 V Step)
G = 1 V/V
G = 100 V/V
Slew Rate (G = 1 V/V)
OFFSET VOLTAGE (RTI)2
Initial, @ +25°C
*
20 kHz
15 kHz
*
150 µs
500 µs
1 V/µs
*
*
*
*
AD210 PIN DESIGNATIONS
Pin
Designation
Function
*
*
*
*
*
*
1
2
3
4
14
15
16
17
18
19
29
30
VO
Output
OCOM
+VOSS
–VOSS
+VISS
–VISS
FB
Output Common
+Isolated Power @ Output
–Isolated Power @ Output
+Isolated Power @ Input
–Isolated Power @ Input
Input Feedback
–Input
±15 ±45/G) mV max
(±10 ±30/G) µV/°C
(±5 ±15/G) mV max
*
*
*
*
*
vs. Temperature (0°C to +70°C)
(–25°C to +85°C) (±10 ±50/G) µV/°C
RATED OUTPUT3
Voltage, 2 kΩ Load
Impedance
Ripple (Bandwidth = 100 kHz)
ISOLATED POWER OUTPUTS4
Voltage, No Load
Accuracy
Current
±10 V min
1 Ω max
10 mV p-p max
*
*
*
*
*
*
–IN
ICOM
+IN
Input Common
+Input
±15 V
±10%
±5 mA
See Text
See Text
*
*
*
*
*
*
*
*
*
*
Pwr Com
Pwr
Power Common
Power Input
Regulation, No Load to Full Load
Ripple
POWER SUPPLY
Voltage, Rated Performance
Voltage, Operating
Current, Quiescent
+15 V dc ± 5%
+15 V dc ± 10%
50 mA
*
*
*
*
*
*
*
*
WARNING!
Current, Full Load – Full Signal
80 mA
TEMPERATURE RANGE
Rated Performance
Operating
–25°C to +85°C
–40°C to +85°C
–40°C to +85°C
*
*
*
*
*
*
ESD SENSITIVE DEVICE
Storage
CAUTION
PACKAGE DIMENSIONS
Inches
Millimeters
1.00 × 2.10 × 0.350
25.4 × 53.3 × 8.9
*
*
*
*
ESD (electrostatic discharge) sensitive device. Elec-
trostatic charges as high as 4000 V readily accumu-
late on the human body and test equipment and can
discharge without detection. Although the AD210
features proprietary ESD protection circuitry, per-
manent damage may occur on devices subjected to
high energy electrostatic discharges. Therefore,
proper ESD precautions are recommended to avoid
performance degradation or loss of functionality.
NOTES
*Specifications same as AD210AN.
1Nonlinearity is specified as a % deviation from a best straight line..
2RTI – Referred to Input.
3A reduced signal swing is recommended when both ±VISS and ±VOSS supplies are fully
loaded, due to supply voltage reduction.
4See text for detailed information.
_
Specifications subject to change without notice.
–2–
REV. A
AD210
R
F
INSIDE THE AD210
V
OUT
16
R
F
= V
1+
(
)
SIG
The AD210 basic block diagram is illustrated in Figure 1.
A +15 V supply is connected to the power port, and
±15 V isolated power is supplied to both the input and
output ports via a 50 kHz carrier frequency. The uncom-
mitted input amplifier can be used to supply gain or buff-
ering of input signals to the AD210. The fullwave
modulator translates the signal to the carrier frequency for
application to transformer T1. The synchronous demodu-
lator in the output port reconstructs the input signal. A
20 kHz, three-pole filter is employed to minimize output
noise and ripple. Finally, an output buffer provides a low
impedance output capable of driving a 2 kΩ load.
R
G
1
17
19
V
SIG
R
AD210
G
2
18
14
15
+V
–V
ISS
+V
3
4
OSS
–V
ISS
OSS
30
29
+15V
Figure 3. Input Configuration for G > 1
Figure 4 shows how to accommodate current inputs or sum cur-
rents or voltages. This circuit configuration can also be used for
signals greater than ±10 V. For example, a ±100 V input span
can be handled with RF = 20 kΩ and RS1 = 200 kΩ.
INPUT
MOD
OUTPUT
16
–IN 17
FB
T1
1
2
DEMOD
FILTER
V
O
19
18
+IN
I
O
COM
COM
I
S
R
F
16
T3
POWER
POWER
T2
+V
–V
+V
–V
3
4
14
15
ISS
OSS
OUTPUT
POWER
SUPPLY
INPUT
POWER
SUPPLY
1
2
17
19
R
ISS
R
OSS
S2
S1
V
OUT
V
V
AD210
OSCILLATOR
S1
S2
AD210
18
14
15
30
29
PWR
PWR COM
+V
–V
ISS
+V
3
4
OSS
Figure 1. AD210 Block Diagram
USING THE AD210
–V
ISS
OSS
30
29
The AD210 is very simple to apply in a wide range of ap-
plications. Powered by a single +15 V power supply, the
AD210 will provide outstanding performance when used
as an input or output isolator, in single and multichannel
configurations.
V
+15V
V
S1
S2
+ I + ...
V
= –R
+
(
S
)
OUT
F
R
R
S1
S2
Figure 4. Summing or Current Input Configuration
Adjustments
Input Configurations: The basic unity gain configura-
tion for signals up to ±10 V is shown in Figure 2. Addi-
tional input amplifier variations are shown in the following
figures. For smaller signal levels Figure 3 shows how to
obtain gain while maintaining a very high input impedance.
When gain and offset adjustments are required, the actual cir-
cuit adjustment components will depend on the choice of input
configuration and whether the adjustments are to be made at
the isolator’s input or output. Adjustments on the output side
might be used when potentiometers on the input side would
represent a hazard due to the presence of high common-mode
voltage during adjustment. Offset adjustments are best done at
the input side, as it is better to null the offset ahead of the gain.
16
V
1
2
OUT
17
19
V
Figure 5 shows the input adjustment circuit for use when the in-
put amplifier is configured in the noninverting mode. This offset
adjustment circuit injects a small voltage in series with the
OUT
(±10V)
V
SIG
AD210
±10V
18
+V
–V
ISS
14
15
GAIN
+V
3
4
OSS
47.5kΩ
16
–V
ISS
OSS
5kΩ
V
OUT
30
29
1
2
17
19
+15V
R
AD210
G
V
Figure 2. Basic Unity Gain Configuration
SIG HI
18
The high input impedance of the circuits in Figures 2 and
3 can be maintained in an inverting application. Since the
AD210 is a three-port isolator, either the input leads or
the output leads may be interchanged to create the signal
inversion.
200Ω
50kΩ
LO
+V
–V
ISS
14
+V
3
4
OSS
100kΩ
15
–V
ISS
OSS
OFFSET
30
29
+15V
Figure 5. Adjustments for Noninverting Input
REV. A
–3–
AD210
low side of the signal source. This will not work if the source has
another current path to input common or if current flows in the
signal source LO lead. To minimize CMR degradation, keep the
resistor in series with the input LO below a few hundred ohms.
CHANNEL OUTPUTS
2
3
1
Figure 5 also shows the preferred gain adjustment circuit. The
circuit shows RF of 50 kΩ, and will work for gains of ten or
greater. The adjustment becomes less effective at lower gains
(its effect is halved at G = 2) so that the pot will have to be a
larger fraction of the total RF at low gain. At G = 1 (follower)
the gain cannot be adjusted downward without compromising
input impedance; it is better to adjust gain at the signal source
or after the output.
0.1"
GRID
POWER
Figure 6 shows the input adjustment circuit for use when the
input amplifier is configured in the inverting mode. The offset
adjustment nulls the voltage at the summing node. This is pref-
erable to current injection because it is less affected by subse-
quent gain adjustment. Gain adjustment is made in the feedback
and will work for gains from 1 V/V to 100 V/V.
GAIN
47.5kΩ
R
R
F
R
R
R
R
G
F
G
F
G
16
5kΩ
V
1
3
2
OUT
1
2
17
19
CHANNEL INPUTS
R
S
Figure 8. PCB Layout for Multichannel Applications with
Gain
200Ω
AD210
V
SIG
18
Synchronization: The AD210 is insensitive to the clock of an
adjacent unit, eliminating the need to synchronize the clocks.
However, in rare instances channel to channel pick-up may
occur if input signal wires are bundled together. If this happens,
shielded input cables are recommended.
50kΩ
+V
–V
ISS
14
+V
3
4
OSS
100kΩ
15
–V
ISS
OSS
OFFSET
30
29
+15V
PERFORMANCE CHARACTERISTICS
Figure 6. Adjustments for Inverting Input
Common-Mode Rejection: Figure 9 shows the common-
mode rejection of the AD210 versus frequency, gain and input
source resistance. For maximum common-mode rejection of
unwanted signals, keep the input source resistance low and care-
fully lay out the input, avoiding excessive stray capacitance at
the input terminals.
Figure 7 shows how offset adjustments can be made at the out-
put, by offsetting the floating output port. In this circuit, ±15 V
would be supplied by a separate source. The AD210’s output
amplifier is fixed at unity, therefore, output gain must be made
in a subsequent stage.
180
16
G = 100
160
140
R
1
LO
= 0
17
G = 1
Ω
V
OUT
19
R
AD210
50kΩ
LO
= 500
2
Ω
18
120
100
R
LO
= 0
200Ω
Ω
0.1µF
+V
–V
ISS
14
15
+V
3
4
OSS
R
LO
= 10k
= 10k
100k
OFFSET
Ω
–V
ISS
OSS
80
60
R
LO
30
29
–15V
+15V
Ω
+15V
Figure 7. Output-Side Offset Adjustment
40
10
20
50 60 100 200
500
1k
2k
5k 10k
PCB Layout for Multichannel Applications: The unique
pinout positioning minimizes board space constraints for multi-
channel applications. Figure 8 shows the recommended printed
circuit board layout for a noninverting input configuration with
gain.
FREQUENCY – Hz
Figure 9. Common-Mode Rejection vs. Frequency
–4–
REV. A
AD210
Phase Shift: Figure 10 illustrates the AD210’s low phase shift
and gain versus frequency. The AD210’s phase shift and wide
bandwidth performance make it well suited for applications like
power monitors and controls systems.
+0.04
+0.03
+0.02
+0.01
0
+8
+6
+4
+2
0
0
60
–20
–40
–60
–80
–100
–120
–140
40
20
φG = 1
–2
–4
–6
–0.01
–0.02
–0.03
–0.04
φG = 100
0
–20
–8
–10 –8
–6
–4
–2
0
+2
+4
+6
+8 +10
–40
–60
OUTPUT VOLTAGE SWING – Volts
Figure 12. Gain Nonlinearity Error vs. Output
0.01
100
90
80
70
60
50
40
30
20
10
0
–80
10
100
1k
10k
100k
0.009
0.008
0.007
0.006
0.005
0.004
0.003
0.002
0.001
0.000
FREQUENCY – Hz
Figure 10. Phase Shift and Gain vs. Frequency
Input Noise vs. Frequency: Voltage noise referred to the input
is dependent on gain and signal bandwidth. Figure 11 illustrates
the typical input noise in nV/√Hz of the AD210 for a frequency
range from 10 to 10 kHz.
60
50
40
0
2
4
6
8
10
12
14
16
18
20
TOTAL SIGNAL SWING – Volts
30
20
Figure 13. Gain Nonlinearity vs. Output Swing
Gain vs. Temperature: Figure 14 illustrates the AD210’s
gain vs. temperature performance. The gain versus temperature
performance illustrated is for an AD210 configured as a unity
gain amplifier.
10
0
400
200
10
100
1k
10k
FREQUENCY – Hz
G = 1
0
Figure 11. Input Noise vs. Frequency
–200
–400
Gain Nonlinearity vs. Output: Gain nonlinearity is defined as the
deviation of the output voltage from the best straight line, and is
specified as % peak-to-peak of output span. The AD210B provides
guaranteed maximum nonlinearity of ±0.012% with an output span of
±10 V. The AD210’s nonlinearity performance is shown in Figure 12.
–600
–800
–1000
–1200
–1400
–1600
Gain Nonlinearity vs. Output Swing: The gain nonlinearity
of the AD210 varies as a function of total signal swing. When
the output swing is less than 20 volts, the gain nonlinearity as a
fraction of signal swing improves. The shape of the nonlinearity
remains constant. Figure 13 shows the gain nonlinearity of the
AD210 as a function of total signal swing.
–25
0
+25
+50
+70
+85
TEMPERATURE – °C
Figure 14. Gain vs. Temperature
REV. A
–5–
AD210
Isolated Power: The AD210 provides isolated power at the
input and output ports. This power is useful for various signal
conditioning tasks. Both ports are rated at a nominal ±15 V at
5 mA.
The isolated power supplies exhibit some ripple which varies as
a function of load. Figure 16a shows this relationship. The
AD210 has internal bypass capacitance to reduce the ripple to a
point where performance is not affected, even under full load.
Since the internal circuitry is more sensitive to noise on the
negative supplies, these supplies have been filtered more heavily.
Should a specific application require more bypassing on the iso-
lated power supplies, there is no problem with adding external
capacitors. Figure 16b depicts supply ripple as a function of
external bypass capacitance under full load.
The load characteristics of the isolated power supplies are
shown in Figure 15. For example, when measuring the load
rejection of the input isolated supplies VISS, the load is placed
between +VISS and –VISS. The curves labeled VISS and VOSS are
the individual load rejection characteristics of the input and the
output supplies, respectively.
1V
There is also some effect on either isolated supply when loading
the other supply. The curve labeled CROSSLOAD indicates the
sensitivity of either the input or output supplies as a function of
the load on the opposite supply.
100mV
30
CROSSLOAD
+V
+V
ISS
10mV
1mV
(
)
OSS
–V
–V
ISS
(
)
25
OSS
V
OSS
100µF
0.1µF
1µF
10µF
SIMULTANEOUS
V
V
OSS
CAPACITANCE
ISS
Figure 16b. Isolated Power Supply Ripple vs. Bypass
Capacitance (Volts p-p, 1 MHz Bandwidth, 5 mA Load)
SIMULTANEOUS
10
V
ISS
20
0
5
APPLICATIONS EXAMPLES
CURRENT – mA
Noise Reduction in Data Acquisition Systems: Transformer
coupled isolation amplifiers must have a carrier to pass both ac
and dc signals through their signal transformers. Therefore,
some carrier ripple is inevitably passed through to the isolator
output. As the bandwidth of the isolator is increased more of the
carrier signal will be present at the output. In most cases, the
ripple at the AD210’s output will be insignificant when com-
pared to the measured signal. However, in some applications,
particularly when a fast analog-to-digital converter is used fol-
lowing the isolator, it may be desirable to add filtering; other-
wise ripple may cause inaccurate measurements. Figure 17
shows a circuit that will limit the isolator’s bandwidth, thereby
reducing the carrier ripple.
Figure 15. Isolated Power Supplies vs. Load
Lastly, the curves labeled VOSS simultaneous and VISS simulta-
neous indicate the load characteristics of the isolated power sup-
plies when an equal load is placed on both supplies.
The AD210 provides short circuit protection for its isolated
power supplies. When either the input supplies or the output
supplies are shorted to input common or output common,
respectively, no damage will be incurred, even under continuous
application of the short. However, the AD210 may be damaged
if the input and output supplies are shorted simultaneously.
+V
OSS
+V
ISS
16
100
75
50
25
0
AD542
R
R
1
17
19
V
–V
V
OUT
OSS
SIG
+V
OSS
ISS
AD210
0.001µF
0.002µF
2
18
14
15
–V
–V
+V
–V
ISS
OSS
+V
3
4
OSS
112.5
C (kHz)
R (kΩ) =
(
)
f
–V
ISS
OSS
30
29
+15V
0
1
2
3
4
5
6
7
Figure 17. 2-Pole, Output Filter
Self-Powered Current Source
The output circuit shown in Figure 18 can be used to create a
LOAD – mA
Figure 16a. Isolated Supply Ripple vs. Load
(External 4.7 µF Bypass)
self-powered output current source using the AD210. The 2 kΩ
resistor converts the voltage output of the AD210 to an equiva-
Under any circumstances, care should be taken to ensure that
the power supplies do not accidentally become shorted.
–6–
REV. A
AD210
lent current VOUT/2 kΩ. This resistor directly affects the output
gain temperature coefficient, and must be of suitable stability for
the application. The external low power op amp, powered by
+VOSS and –VOSS, maintains its summing junction at output
common. All the current flowing through the 2 kΩ resistor flows
through the output Darlington pass devices. A Darlington con-
figuration is used to minimize loss of output current to the base.
monitors the input terminal (cold-junction). Ambient tempera-
ture changes from 0°C to +40°C sensed by the AD590, are can-
celled out at the cold junction. Total circuit gain equals 183;
100 and 1.83, from A1 and the AD210 respectively. Calibration
is performed by replacing the thermocouple junction with plain
thermocouple wire and a millivolt source set at 0.0000 V (0°C)
and adjusting RO for EOUT equal to 0.000 V. Set the millivolt
source to +0.02185 V (400°C) and adjust RG for VOUT equal to
+4.000 V. This application circuit will produce a nonlinearized
output of about +10 mV/°C for a 0°C to +400°C range.
FDH333
16
+V
2kΩ
OSS
2N3906
(2)
1
17
19
V
SIG
LF441
–V
–V
R
5k
ISS
G
1000pF
0-10V
AD590
OSS
AD210
13.7k 10k
THERMAL
2
16
18
14
15
CONTACT
"J"
V
OUT
AD OP-07
1
I
17
19
OUT
+V
ISS
3
4
+V
–V
OSS
A1
AD210
–V
ISS
OSS
2
52.3Ω
220pF
18
I
OUT
30
29
COLD
JUNCTION
RETURN
+15V
3
4
+V
–V
RG
OSS
14
15
+V
ISS
100k
1k
Figure 18. Self-Powered Isolated Current Source
10k
–V
ISS
OSS
-20k-
+V
30
29
The low leakage diode is used to protect the base-emitter junc-
tion against reverse bias voltages. Using –VOSS as a current
return allows more than 10 V of compliance. Offset and gain
control may be done at the input of the AD210 or by varying
the 2 kΩ resistor and summing a small correction current
directly into the summing node. A nominal range of 1 mA–
5 mA is recommended since the current output cannot reach
zero due to reverse bias and leakage currents. If the AD210 is
powered from the input potential, this circuit provides a fully
isolated, wide bandwidth current output. This configuration is
limited to 5 mA output current.
–V
ISS
ISS
+15V
Figure 20. Isolated Thermocouple Amplifier
Precision Floating Programmable Reference
The AD210, when combined with a digital-to-analog converter,
can be used to create a fully floating voltage output. Figure 21
shows one possible implementation.
The digital inputs of the AD7541 are TTL or CMOS compat-
ible. Both the AD7541 and AD581 voltage reference are pow-
ered by the isolated power supply + VISS. ICOM should be tied to
input digital common to provide a digital ground reference for
the inputs.
Isolated V-to-I Converter
Illustrated in Figure 19, the AD210 is used to convert a 0 V to
+10 V input signal to an isolated 4–20 mA output current. The
AD210 isolates the 0 V to +10 V input signal and provides a
proportional voltage at the isolator’s output. The output circuit
converts the input voltage to a 4–20 mA output current, which
The AD7541 is a current output DAC and, as such, requires an
external output amplifier. The uncommitted input amplifier
internal to the AD210 may be used for this purpose. For best
results, its input offset voltage must be trimmed as shown.
in turn is applied to the loop load RLOAD
.
The output voltage of the AD210 will go from 0 V to –10 V for
digital inputs of 0 and full scale, respectively. However, since
the output port is truly isolated, VOUT and OCOM may be freely
interchanged to get 0 V to +10 V.
+28V
CURRENT
LOOP
ADJUST
TO 4mA
WITH 0V IN
500Ω
143Ω
3.0k
2N2907
This circuit provides a precision 0 V–10 V programmable refer-
ence with a ±3500 V common-mode range.
16
+V
ISS
1
+V
S
GAIN
2kΩ
17
19
2N2219
AD308
V
SIG
AD581
–V
S
+V
ISS
AD210
2
17 16
18
14
15
1kΩ
576Ω
100Ω
16
17
19
18
1
4
SPAN
ADJ
12-BIT
DIGITAL
INPUT
V
OUT
+V
ISS
3
4
1
2
+V
–V
OSS
0 - –10V
15
2
CURRENT
LOOP
–V
ISS
OSS
1N4149
AD210
200Ω
3
30
29
18
R
LOAD
50kΩ
+15V
HP5082-2811
OR EQUIVALENT
14
+V
ISS
3
4
+V
OSS
Figure 19. Isolated Voltage-to-Current Loop Converter
100kΩ
15
–V
ISS
Isolated Thermocouple Amplifier
–V
OSS
OFFSET
30
29
The AD210 application shown in Figure 20 provides amplifica-
tion, isolation and cold-junction compensation for a standard J
type thermocouple. The AD590 temperature sensor accurately
+15V
Figure 21. Precision Floating Programmable Reference
REV. A
–7–
AD210
200kΩ
8.25k
10T
AD210
16
17
19
R
1kΩ
G
1
2
CHANNEL 1
18
14
4-20mA
25Ω
1kΩ
+V
ISS
50k
+V
3
4
R
50k
OSS
O
–V
–V
15
OSS
ISS
10T
30
29
R
F
15.8k
+V –V
AD210
COM
16
17
19
R
5k
G
1
2
10T
R
O
AD590
–V
1kΩ
CHANNEL 2
18
14
9.31k
ISS
+V
ISS
50k
+V
3
4
OSS
OFFSET
50k
+V
ISS
AD7502
MULTIPLEXER
–V
–V
15
OSS
ISS
AD580
39k
TO A/D
100Ω
10T
30
30
30
29
AD210
16
17
19
+V
ISS
AD OP-07
1
2
CHANNEL 3
18
E
–V
IN
ISS
1.0µF
0.47µF
14
15
+V
+V
3
4
ISS
OSS
CHANNEL
SELECT
50Ω
50kΩ
–V
–V
OSS
ISS
29
+V
ISS
AD210
16
17
19
+V
A2
–V
ISS
+10V
1
2
AD584
20k
20k
CHANNEL 4
18
ISS
14
15
+V
ISS
+V
ISS 20k
+V
3
4
20k
OSS
1M
1k
–V
–V
OSS
ISS
A1
–V
29
COM
+15V
DC POWER
SOURCE
ISS
A1 A2 = AD547
Figure 22. Multichannel Data Acquisition Front-End
MULTICHANNEL DATA ACQUISITION FRONT-END
Illustrated in Figure 22 is a four-channel data acquisition front-
end used to condition and isolate several common input signals
found in various process applications. In this application, each
AD210 will provide complete isolation from input to output as
well as channel to channel. By using an isolator per channel,
maximum protection and rejection of unwanted signals is
obtained. The three-port design allows the AD210 to be
configured as an input or output isolator. In this application the
isolators are configured as input devices with the power port
providing additional protection from possible power source
faults.
AD580 reference circuit provides an equal but opposite current,
resulting in a zero net current flow, producing a 0 V output from
the AD210. At +100°C (+212°F), the AD590 current output will
be 373.2 µA minus the 255.4 µA offsetting current from the
AD580 circuit to yield a +117.8 µA input current. This current is
converted to a voltage via RF and RG to produce an output of
+2.12 V. Channel 2 will produce an output of +10 mV/°F over a
0°F to +212°F span.
Channel 3: Channel 3 is a low level input channel configured with
a high gain amplifier used to condition millivolt signals. With the
AD210’s input set to unity and the input amplifier set for a gain of
1000, a ±10 mV input will produce a ±10 V at the AD210’s output.
Channel 1: The AD210 is used to convert a 4–20 mA current
loop input signal into a 0 V–10 V input. The 25 Ω shunt resistor
converts the 4-20 mA current into a +100 mV to +500 mV signal.
The signal is offset by –100 mV via RO to produce a 0 mV to
+400 mV input. This signal is amplified by a gain of 25 to produce
the desired 0 V to +10 V output. With an open circuit, the AD210
will show –2.5 V at the output.
Channel 4: Channel 4 illustrates one possible configuration for
conditioning a bridge circuit. The AD584 produces a +10 V
excitation voltage, while A1 inverts the voltage, producing negative
excitation. A2 provides a gain of 1000 V/V to amplify the low level
bridge signal. Additional gain can be obtained by reconfiguration
of the AD210’s input amplifier. ±VISS provides the complete power
for this circuit, eliminating the need for a separate isolated excita-
tion source.
Channel 2: In this channel, the AD210 is used to condition and
isolate a current output temperature transducer, Model AD590. At
+25°C, the AD590 produces a nominal current of 298.2 µA. This
level of current will change at a rate of 1 µA/°C. At –17.8°C (0°F),
the AD590 current will be reduced by 42.8 µA to +255.4 µA. The
Each channel is individually addressed by the multiplexer’s chan-
nel select. Additional filtering or signal conditioning should follow
the multiplexer, prior to an analog-to-digital conversion stage
.
–8–
REV. A
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