a
FEATURES
Small Size: 4 Channels/lnch
Low Power: 35 mW (AD204)
High Accuracy: 0.025% Max Nonlinearity (K Grade)
High CMR: 130 dB (Gain = 100 V/V)
Wide Bandwidth: 5 kHz Full-Power (AD204)
High CMV Isolation: 2000 V pk Continuous (K Grade)
(Signal and Power)
Isolated Power Outputs
Uncommitted Input Amplifier
APPLICATIONS
Multichannel Data Acquisition
Current Shunt Measurements
Motor Controls
Process Signal Isolation
High Voltage Instrumentation Amplifier
GENERAL DESCRIPTION
Low Cost, Miniature
Isolation Amplifiers
AD202/AD204
PRODUCT HIGHLIGHTS
The AD202 and AD204 are full-featured isolators offering
numerous benefits to the user:
Small Size:
The AD202 and AD204 are available in SIP and
DIP form packages. The SIP package is just 0.25" wide, giving
the user a channel density of four channels per inch. The isolation
barrier is positioned to maximize input to output spacing. For
applications requiring a low profile, the DIP package provides a
height of just 0.350".
High Accuracy:
With a maximum nonlinearity of
±
0.025%
for the AD202K/AD204K (± 0.05% for the AD202J/AD204J)
and low drift over temperature, the AD202 and AD204 provide
high isolation without loss of signal integrity.
Low Power:
Power consumption of 35 mW (AD204) and
75 mW (AD202) over the full signal range makes these isolators
ideal for use in applications with large channel counts or tight
power budgets.
Wide Bandwidth:
The AD204’s full-power bandwidth of 5 kHz
makes it useful for wideband signals. It is also effective in appli-
cations like control loops, where limited bandwidth could result
in instability.
Excellent Common-Mode Performance:
The AD202K/
AD204K provide
±
2000 V pk continuous common-mode isola-
tion, while the AD202J/AD204J provide
±
1000 V pk continuous
common-mode isolation. All models have a total common-mode
input capacitance of less than 5 pF inclusive of power isolation.
This results in CMR ranging from 130 dB at a gain of 100 dB to
104 dB (minimum at unity gain) and very low leakage current
(2
mA
maximum).
Flexible Input:
An uncommitted op amp is provided at the
input of all models. This provides buffering and gain as required,
and facilitates many alternative input functions including filtering,
summing, high voltage ranges, and current (transimpedance) input.
Isolated Power:
The AD204 can supply isolated power of
±
7.5 V at 2 mA. This is sufficient to operate a low-drift input
preamp, provide excitation to a semiconductor strain gage, or
power any of a wide range of user-supplied ancillary circuits.
The AD202 can supply
±
7.5 V at 0.4 mA, which is sufficient to
operate adjustment networks or low power references and op
amps, or to provide an open-input alarm.
The AD202 and AD204 are general purpose, two-port, trans-
former-coupled isolation amplifiers that may be used in a broad
range of applications where input signals must be measured,
processed, and/or transmitted without a galvanic connection.
These industry standard isolation amplifiers offer a complete
isolation function, with both signal and power isolation provided
for in a single compact plastic SIP or DIP style package. The
primary distinction between the AD202 and the AD204 is that
the AD202 is powered directly from a 15 V dc supply while the
AD204 is powered by an externally supplied clock, such as the
recommended AD246 Clock Driver.
The AD202 and AD204 provide total galvanic isolation between
the input and output stages of the isolation amplifier through
the use of internal transformer-coupling. The functionally com-
plete AD202 and AD204 eliminate the need for an external,
user-supplied dc-to-dc converter. This permits the designer
to minimize the necessary circuit overhead and consequently
reduce the overall design and component costs.
The design of the AD202 and AD204 emphasizes maximum
flexibility and ease of use, including the availability of an
uncommitted op amp on the input stage. They feature a bipolar
±
5 V output range, an adjustable gain range of from 1V/V to
100 V/V,
±
0.025% max nonlinearity (K grade), 130 dB of
CMR, and the AD204 consumes a low 35 mW of power.
The functional block diagrams can be seen in Figures 1a and 1b.
REV. D
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 that
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: 781/329-4700
www.analog.com
Fax: 781/326-8703
© Analog Devices, Inc., 2002
AD202/AD204–SPECIFICATIONS
(Typical @ 25 C and V = 15 V unless otherwise noted.)
S
Model
GAIN
Range
Error
vs. Temperature
vs. Time
vs. Supply Voltage
Nonlinearity (G = 1 V/V)
1
Nonlinearity vs. Isolated Supply Load
INPUT VOLTAGE RATINGS
Input Voltage Range
Max lsolation Voltage (Input to Output)
AC, 60 Hz, Continuous
Continuous (AC and DC)
Isolation-Mode Rejection Ratio (IMRR) @ 60 Hz
R
S
£
100
W
(HI and LO Inputs) G = 1 V/V
G = 100 V/V
R
S
£
l kW (Input HI, LO, or Both) G = 1 V/V
G = 100 V/V
Leakage Current Input to Output @ 240 V rms, 60 Hz
INPUT IMPEDANCE
Differential (G = 1 V/V)
Common-Mode
INPUT BIAS CURRENT
Initial, @ 25∞C
vs. Temperature (0∞C to 70∞C)
INPUT DIFFERENCE CURRENT
Initial, @ 25∞C
vs. Temperature (0∞C to 70∞C)
INPUT NOISE
Voltage, 0.1 Hz to 100 Hz
f > 200 Hz
FREQUENCY RESPONSE
Bandwidth (V
O
£
10 V p-p, G = 1 V–50 V/V)
Settling Time, to
±
10 mV (10 V Step)
OFFSET VOLTAGE (RTI)
Initial, @ 25∞C Adjustable to Zero
vs. Temperature (0∞C to 70∞C)
RATED OUTPUT
Voltage (Out HI to Out LO)
Voltage at Out HI or Out LO (Ref. Pin 32)
Output Resistance
Output Ripple, 100 kHz Bandwidth
5 kHz Bandwidth
ISOLATED POWER OUTPUT
2
Voltage, No Load
Accuracy
Current
Regulation, No Load to Full Load
Ripple
OSCILLATOR DRIVE INPUT
Input Voltage
Input Frequency
POWER SUPPLY (AD202 Only)
Voltage, Rated Performance
Voltage, Operating
Current, No Load (V
S
= 15 V)
TEMPERATURE RANGE
Rated Performance
Operating
Storage
PACKAGE DIMENSIONS
4
SIP Package (Y)
DlP Package (N)
NOTES
*Specifications
same as AD204J.
1
Nonlinearity is specified as a % deviation from a best straight line.
2
1.0
mF
min decoupling required (see text).
AD204J
1 V/V–100 V/V
±
0.5% typ (± 4% max)
±
20 ppm/∞C typ (± 45 ppm/∞C max)
±
50 ppm/1000 Hours
±
0.01%/V
±
0.05% max
±
0.0015%/mA
±
5 V
750 V rms
±
1000 V Peak
110 dB
130 dB
104 dB min
110 dB min
2
mA
rms max
10
12
W
2 GW 4.5 pF
±
30 pA
±
10 nA
±
5 pA
±
2 nA
4
mV
p-p
50 nV/÷Hz
5 kHz
1 ms
(± 15
±
15/G)mV max
Ê
10
ˆ
Á
±
10
±
G
˜
m
V
∞
C
Ë
¯
AD204K
*
*
*
*
±
0.01%/V
±
0.025% max
*
*
1500 V rms
±
2000 V Peak
110 dB
*
104 dB min
*
*
*
*
*
*
*
*
*
*
5 kHz
*
(± 5
±
5/G) mV max
*
AD202J
*
*
*
*
±
0.01%/V
±
0.05% max
*
*
750 V rms
±
1000 V Peak
105 dB
*
100 dB min
*
*
*
*
*
*
*
*
*
*
2 kHz
*
AD202K
*
*
*
*
±
0.01%/V
±
0.025% max
*
*
1500 V rms
±
2000 V Peak
105 dB
*
100 dB min
*
*
*
*
*
*
*
*
*
*
2 kHz
*
(± 15
±
15/G) mV max (± 5
±
5/G) mV max
*
*
±
5 V
±
6.5 V
3 kW
10 mV p-p
0.5 mV rms
±
7.5 V
±
10%
2 mA (Either Output)
3
5%
100 mV p-p
15 V p-p Nominal
25 kHz Nominal
N/A
N/A
N/A
0∞C to 70∞C
–40∞C to +85∞C
–40∞C to +85∞C
2.08"
¥
0.250"
¥
0.625"
2.10"
¥
0.700"
¥
0.350"
3
4
*
*
3 kW
*
*
*
*
2 mA (Either Output)
3
*
*
15 V p-p Nominal
25 kHz Nominal
N/A
N/A
N/A
*
*
*
*
*
*
*
7 kW
*
*
*
*
400
mA
Total
*
*
N/A
N/A
15 V
±
5%
15 V
±
10%
5 mA
*
*
*
*
*
*
*
7 kW
*
*
*
*
400
mA
Total
*
*
N/A
N/A
15 V
±
5%
15 V
±
10%
5 mA
*
*
*
*
*
3 mA with one supply loaded.
Width is 0.25" typ, 0.26" max.
Specifications subject to change without notice.
–2–
REV. D
AD202/AD204
AD246–SPECIFICATIONS
(Typical @ 25∞C and V
S
= 15 V unless otherwise noted.)
PIN DESIGNATIONS
AD202/AD204 SIP Package
Model
OUTPUT
l
Frequency
Voltage
Fan-Out
POWER SUPPLY
REQUIREMENTS
Input Voltage
Supply Current
Unloaded
Each AD204 Adds
Each 1 mA Load on AD204
+V
ISO
or –V
ISO
Adds
AD246JY
AD246JN
Pin
1
2
3
4
5
6
31
32
33
37
38
Function
+INPUT
INPUT/V
ISO
COMMON
–INPUT
INPUT FEEDBACK
–V
ISO
OUTPUT
+V
ISO
OUTPUT
15 V POWER IN (AD202 ONLY)
CLOCK/POWER COMMON
CLOCK INPUT (AD204 ONLY)
OUTPUT LO
OUTPUT HI
AD202/AD204 DIP Package
25 kHz Nominal
*
15 V p-p Nominal
*
32 Max
*
15 V
±
5%
35 mA
2.2 mA
0.7 mA
*
*
*
*
NOTES
*Specifications
the same as the AD246JY.
1
The high current drive output will not support a short to ground.
Specifications subject to change without notice.
Pin
AD246 Pin Designations
Function
+INPUT
INPUT/V
ISO
COMMON
–INPUT
OUTPUT LO
OUTPUT HI
15 V POWER IN (AD202 ONLY)
CLOCK INPUT (AD204 ONLY)
CLOCK/POWER COMMON
+V
ISO
OUTPUT
–V
ISO
OUTPUT
INPUT FEEDBACK
Pin (Y)
1
2
12
13
Pin (N)
12
1
14
24
Function
15 V POWER IN
CLOCK OUTPUT
COMMON
COMMON
1
2
3
18
19
20
21
22
36
37
38
ORDERING GUIDE
Model
AD202JY
AD202KY
AD202JN
AD202KN
AD204JY
AD204KY
AD204JN
AD204KN
Package
Option
SIP
SIP
DIP
DIP
SIP
SIP
DIP
DIP
Max Common-Mode
Voltage (Peak)
1000 V
2000 V
1000 V
2000 V
1000 V
2000 V
1000 V
2000 V
Max
Linearity
±
0.05%
±
0.025%
±
0.05%
±
0.025%
±
0.05%
±
0.025%
±
0.05%
±
0.025%
CAUTION
ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily
accumulate on the human body and test equipment and can discharge without detection. Although
the AD202/AD204 features proprietary ESD protection circuitry, permanent 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.
WARNING!
ESD SENSITIVE DEVICE
REV. D
–3–
AD202/AD204
DIFFERENCES BETWEEN THE AD202 AND AD204
The primary distinction between the AD202 and AD204 is in
the method by which they are powered: the AD202 operates
directly from 15 V dc while the AD204 is powered by a non-
isolated externally-supplied clock (AD246) that can drive up to
32 AD204s. The main advantages of using the externally-
clocked AD204 over the AD202 are reduced cost in multichannel
applications, lower power consumption, and higher bandwidth.
In addition, the AD204 can supply substantially more isolated
power than the AD202.
Of course, in a great many situations, especially where only one
or a few isolators are used, the convenience of standalone opera-
tion provided by the AD202 will be more significant than any
of the AD204’s advantages. There may also be cases where it is
desirable to accommodate either device interchangeably, so the
pinouts of the two products have been designed to make that
easy to do.
FB
IN–
IN+
V
SIG
IN COM
+V
ISO
OUT
–V
ISO
OUT
+7.5V
–7.5V
RECT
AND
FILTER
POWER
OSCILLATOR
25kHz
25kHz
15V DC
5V
FS
MOD
5V
FS
SIGNAL
the output leads to get signal inversion. Additionally, in multi-
channel applications, the unbuffered outputs can be multiplexed
with one buffer following the mux. This technique minimizes
offset errors while reducing power consumption and cost. The
output resistance of the isolator is typically 3 kΩ for the AD204
(7 kΩ for AD202) and varies with signal level and temperature,
so it should not be loaded (see Figure 2 for the effects of load
upon nonlinearity and gain drift). In many cases, a high imped-
ance load will be present or a following circuit such as an output
filter can serve as a buffer so that a separate buffer function will
not often be needed.
NON-
LINEARITY
(%)
0.25
GAIN
GAIN TC
CHANGE CHANGE
(%)
(ppm/ C)
–10
–500
0.20
–8
–400
AD202
DEMOD
HI
V
OUT
LO
0.15
AD202 GAIN AND GAIN TC
AD202 NONLINEARITY
–6
–300
0.10
AD204 GAIN AND GAIN TC
–4
–200
0.05
–2
–100
AD204 NONLINEARITY
POWER
RETURN
0
0
0.1
0.2
0.3
0.4
0.5
0.6
OUTPUT LOAD – M
0.7
0.8
0.9
0
1.0
0
Figure 1a. AD202 Functional Block Diagram
FB
IN–
IN+
V
SIG
IN COM
+V
ISO
OUT
–V
ISO
OUT
+7.5V
–7.5V
RECT
AND
FILTER
POWER
25kHz
POWER
CONV.
CLOCK
15V p-p
25kHz
POWER
RETURN
5V
FS
MOD
5V
FS
SIGNAL
Figure 2. Effects of Output Loading
USING THE AD202 AND AD204
AD204
DEMOD
HI
LO
V
OUT
Powering the AD202.
The AD202 requires only a single 15 V
power supply connected as shown in Figure 3a. A bypass capaci-
tor is provided in the module.
AD202
15V
5%
25kHz
15V RETURN
Figure 1b. AD204 Functional Block Diagram
(Pin Designations Apply to the DIP-Style Package)
Figure 3a.
INSIDE THE AD202 AND AD204
The AD202 and AD204 use an amplitude modulation technique
to permit transformer coupling of signals down to dc (Figure 1a
and 1b). Both models also contain an uncommitted input op
amp and a power transformer that provides isolated power to
the op amp, the modulator, and any external load. The power
transformer primary is driven by a 25 kHz, 15 V p-p square
wave generated internally in the case of the AD202, or supplied
externally for the AD204.
Within the signal swing limits of approximately
±
5 V, the out-
put voltage of the isolator is equal to the output voltage of the
op amp; that is, the isolation barrier has unity gain. The output
signal is not internally buffered, so the user is free to interchange
Powering the AD204.
The AD204 gets its power from an
externally supplied clock signal (a 15 V p-p square wave with a
nominal frequency of 25 kHz) as shown in Figure 3b.
AD246
AD204
AD204
AD204
+
15V
15V RETURN
Figure 3b.
(NOTE: Circuit figures shown on this page are for SIP-style packages. Refer to
Page 3 for proper DIP package pinout.)
–4–
REV. D
AD202/AD204
AD246 Clock Driver.
The AD246 is a compact, inexpensive
clock driver that can be used to obtain the required clock from a
single 15 V supply. Alternatively, the circuit shown in Figure 4
(essentially an AD246) can be used. In either case, one clock
circuit can operate at least 32 AD204s at the rated minimum
supply voltage of 14.25 V and one additional isolator can be
operated for each 40 mV increase in supply voltage up to 15 V.
A supply bypass capacitor is included in the AD246, but if many
AD204s are operated from a single AD246, an external bypass
capacitor should be used with a value of at least 1
mF
for every
five isolators used. Place the capacitor as close as possible to the
clock driver.
15V
14
180pF
1
3
2
49.9k
12 9
8
7
4
C
RC
R
CD
4047B
Q
6
5
6
TELEDYNE
TSC426
10
2
4
1N914
7
5
1N914
3
CLK
OUT
+1 F
35V
CLK AND
PWR COM
100pF
2k
V
SIG
R
F
AD202
OR
AD204
V
O
R
(
1 + –––
)
R
F
G
R
G
V
O
= V
SIG
R
F
20k
Figure 6. Input Connections for Gain > 1
The noninverting circuit of Figures 5 and 6 can also be used to
your advantage when a signal inversion is needed: just interchange
either the input leads or the output leads to get inversion. This
approach retains the high input resistance of the noninverting
circuit, and at unity gain no gain-setting resistors are needed.
When the isolator is not powered, a negative input voltage of
more than about 2 V will cause an input current to flow. If the
signal source can supply more than a few mA under such con-
ditions, the 2 kW resistor shown in series with IN+ should be
used to limit current to a safe value. This is particularly impor-
tant with the AD202, which may not start if a large input current
is present.
Figure 7 shows how to accommodate current inputs or sum
currents or voltages. This circuit can also be used when the
input signal is larger than the
±
5 V input range of the isolator;
for example, a
±
50 V input span can be accommodated with
R
F
= 20 kW and R
S
= 200 kW. Once again, a capacitor from FB
to IN COM is required for gains above five.
I
S
R
F
Figure 4. Clock Driver
Input Configurations.
The AD202 and AD204 have been
designed to be very easy to use in a wide range of applications.
The basic connection for standard unity gain applications, useful
for signals up to
±
5 V, is shown in Figure 5; some of the possible
variations are described below. When smaller signals must be
handled, Figure 6 shows how to achieve gain while preserving a
very high input resistance. The value of feedback resistor R
F
should be kept above 20 kW for best results. Whenever a gain of
more than five is taken, a 100 pF capacitor from FB to IN COM
is required. At lower gains this capacitor is unnecessary, but it
will not adversely affect performance if used.
FB
2k
(SEE TEXT)
V
SIG
( 5V)
IN–
IN+
OUT
LO
V
OUT
5V
OUT
HI
R
S2
V
S2
R
S1
V
S1
AD202
OR
AD204
V
IN COM
R
F
R
F
V = – V
S1
––– + V
S2
––– + I
S
R
F
+ ...
R
S1
R
S2
R
F
20k
(
)
AD202
OR
AD204
15V OR
CLOCK
Figure 7. Connections for Summing or Current Inputs
Figure 5. Basic Unity-Gain Application
(NOTE: Circuit figures shown on this page are for SIP-style packages. Refer to
Page 3 for proper DIP package pinout.)
REV. D
–5–
Analogue and Mixed Signal
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