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부품번호 AD202 기능
기능 Low Cost / Miniature Isolation Amplifiers
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AD202 데이터시트, 핀배열, 회로
a
Low Cost, Miniature
Isolation Amplifiers
AD202/AD204
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
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.
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.
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 pdf, 반도체, 판매, 대치품
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.
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 kfor the AD204
(7 kfor 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
FB
IN–
IN+
VSIG
IN COM
+VISO OUT
–VISO OUT
؎5V
FS
SIGNAL
MOD
AD202
DEMOD
؎5V
FS
HI
VOUT
LO
+7.5V
–7.5V
RECT
AND
FILTER
POWER
OSCILLATOR
25kHz
25kHz
15V DC
POWER
RETURN
Figure 1a. AD202 Functional Block Diagram
FB
IN–
IN+
VSIG
IN COM
+VISO OUT
–VISO OUT
؎5V
FS
SIGNAL
MOD
AD204
DEMOD
؎5V
FS
HI
VOUT
LO
+7.5V
–7.5V
RECT
AND
FILTER
POWER
25kHz 25kHz
POWER
CONV.
CLOCK
15V p-p
25kHz
POWER
RETURN
Figure 1b. AD204 Functional Block Diagram
(Pin Designations Apply to the DIP-Style Package)
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
0.15
AD202 GAIN AND GAIN TC
AD202 NONLINEARITY
0.10
AD204 GAIN AND GAIN TC
–6 –300
–4 –200
0.05
–2 –100
AD204 NONLINEARITY
00
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
OUTPUT LOAD – M
Figure 2. Effects of Output Loading
0
USING THE AD202 AND AD204
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%
15V RETURN
Figure 3a.
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.
AD204
AD204
AD204
AD246
+
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

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AD202 전자부품, 판매, 대치품
AD202/AD204
180
G = 100
160 G = 1
140 RLO = 0
120 RLO = 500
100 RLO = 0
80
RLO = 10k
RLO = 10k
60
40
10
20
50 60 100 200
500
FREQUENCY – Hz
1k
2k
5k
Figure 10b. AD202
Dynamics and Noise. Frequency response plots for the AD202
and AD204 are given in Figure 11. Since neither isolator is slew-
rate limited, the plots apply for both large and small signals.
Capacitive loads of up to 470 pF will not materially affect fre-
quency response. When large signals beyond a few hundred Hz
will be present, it is advisable to bypass –VISO and +VISO to IN
COM with 1 mF tantalum capacitors even if the isolated supplies
are not loaded.
At 50 Hz/60 Hz, phase shift through the AD202/AD204 is typically
0.8(lagging). Typical unit to unit variation is ±0.2(lagging).
60
AD204
AD202
40
20
AMPLITUDE
RESPONSE
0
PHASE
RESPONSE
(G = 1)
–20
0
–50
–40
10 20
50 100 200 500 1k 2k
FREQUENCY – Hz
–100
5k 10k 20k
Figure 11. Frequency Response at Several Gains
The step response of the AD204 for very fast input signals can
be improved by the use of an input filter, as shown in Figure 12.
The filter limits the bandwidth of the input (to about 5.3 kHz)
so that the isolator does not see fast, out-of-band input terms
that can cause small amounts (± 0.3%) of internal ringing. The
AD204 will then settle to ± 0.1% in about 300 ms for a 10 V
step.
AD204
3.3k
VS 0.01F
Except at the highest useful gains, the noise seen at the output
of the AD202 and AD204 will be almost entirely comprised of
carrier ripple at multiples of 25 kHz. The ripple is typically
2 mV p-p near zero output and increases to about 7 mV p-p for
outputs of ± 5 V (1 MHz measurement bandwidth). Adding a
capacitor across the output will reduce ripple at the expense of
bandwidth: for example, 0.05 mF at the output of the AD204
will result in 1.5 mV ripple at ± 5 V, but signal bandwidth will
be down to 1 kHz.
When the full isolator bandwidth is needed, the simple two-pole
active filter shown in Figure 13 can be used. It will reduce ripple
to 0.1 mV p-p with no loss of signal bandwidth, and also serves
as an output buffer.
An output buffer or filter may sometimes show output spikes
that do not appear at its input. This is usually due to clock noise
appearing at the op amp’s supply pins (since most op amps have
little or no supply rejection at high frequencies). Another com-
mon source of carrier-related noise is the sharing of a ground
track by both the output circuit and the power input. Figure 13
shows how to avoid these problems: the clock/supply port of the
isolator does not share ground or 15 V tracks with any signal
circuits, and the op amp’s supply pins are bypassed to signal
common (note that the grounded filter capacitor goes here as
well). Ideally, the output signal LO lead and the supply com-
mon meet where the isolator output is actually measured, e.g.,
at an A/D converter input. If that point is more than a few feet
from the isolator, it may be useful to bypass output LO to sup-
ply common at the isolator with a 0.1 mF capacitor.
In applications where more than a few AD204s are driven by a
single clock driver, substantial current spikes will flow in the
power return line and in whichever signal out lead returns to a
low impedance point (usually output LO). Both of these tracks
should be made large to minimize inductance and resistance;
ideally, output LO should be directly connected to a ground
plane which serves as measurement common.
Current spikes can be greatly reduced by connecting a small
inductance (68 mH–100 mH) in series with the clock pin of each
AD204. Molded chokes such as the Dale IM-2 series, with dc
resistance of about 5 W, are suitable.
10k
2200pF
10k
1000pF
AD711
++
1.0F 1.0F
POINT OF
MEASUREMENT
AD202
OR
AD204
AD246
(IF USED)
–15V C +15V
POWER
SUPPLY
Figure 13. Output Filter Circuit Showing Proper Grounding
Figure 12. Input Filter for Improved Step Response
REV. D
(NOTE: Circuit figures shown on this page are for SIP-style packages. Refer to
Page 3 for proper DIP package pinout.)
–7–

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