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PDF ( 数据手册 , 数据表 ) AD204

零件编号 AD204
描述 Low Cost / Miniature Isolation Amplifiers
制造商 Analog Devices
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AD204 数据手册, 描述, 功能
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







AD204 pdf, 数据表
AD202/AD204
Using Isolated Power. Both the AD202 and the AD204 provide
±7.5 V power outputs referenced to input common. These may be
used to power various accessory circuits that must operate at
the input common-mode level; the input zero adjustment pots
described above are an example, and several other possible uses
are shown in the section titled Application Examples.
The isolated power output of the AD202 (400 mA total from
either or both outputs) is much more limited in current capacity
than that of the AD204, but it is sufficient for operating micro-
power op amps, low power references (such as the AD589),
adjustment circuits, and the like.
The AD204 gets its power from an external clock driver, and
can handle loads on its isolated supply outputs of 2 mA for each
supply terminal (+7.5 V and –7.5 V) or 3 mA for a single loaded
output. Whenever the external load on either supply is more
than about 200 mA, a 1 mF tantalum capacitor should be used to
bypass each loaded supply pin to input common.
Up to 32 AD204s can be driven from a single AD246 (or equi-
valent) clock driver when the isolated power outputs of the
AD204s are loaded with less than 200 mA each, at a worst-case
supply voltage of 14.25 V at the clock driver. The number of
AD204s that can be driven by one clock driver is reduced by
one AD204 per 3.5 mA of isolated power load current at 7.5 V,
distributed in any way over the AD204s being supplied by that
clock driver. Thus a load of 1.75 mA from +VISO to –VISO would
also count as one isolator because it spans 15 V.
It is possible to increase clock fanout by increasing supply volt-
age above the 14.25 V minimum required for 32 loads. One
additional isolator (or 3.5 mA unit load) can be driven for each
40 mV of increase in supply voltage up to 15 V. Therefore if the
minimum supply voltage can be held to 15 V – 1%, it is possible
to operate 32 AD204s and 52 mA of 7.5 V loads. Figure 14
shows the allowable combinations of load current and channel
count for various supply voltages.
50
IISO = 0mA TOTAL
40
IISO = 35mA TOTAL
30
IISO = 70mA TOTAL
IISO =TO80TmALA
20
10 OPERATION IN THIS REGION EXCEEDS
4mA LOAD LIMIT PER AD204
0
14.25
14.50
14.75
MINIMUM SUPPLY VOLTAGE
Figure 14. AD246 Fanout Rules
15.0
Operation at Reduced Signal Swing. Although the nominal
output signal swing for the AD202 and AD204 is ± 5 V, there
may be cases where a smaller signal range is desirable. When
that is done, the fixed errors (principally offset terms and output
noise) become a larger fraction of the signal, but nonlinearity is
reduced. This is shown in Figure 15.
0.025
0.020
0.015
0.010
0.005
0
012 34 5
OUTPUT SIGNAL SWING – ؎V
Figure 15. Nonlinearity vs. Signal Swing
PCB Layout for Multichannel Applications. The pinout of
the AD204Y has been designed to make very dense packing
possible in multichannel applications. Figure 16a shows the
recommended printed circuit board (PCB) layout for the simple
voltage-follower connection. When gain-setting resistors are
present, 0.25" channel centers can still be achieved, as shown in
Figure 16b.
CHANNEL INPUTS
0 12
0.1”
GRID
CLK COM
CLK
OUT COM
CHANNEL OUTPUTS
TO MUX
Figure 16a.
(NOTE: Circuit figures shown on this page are for SIP-style packages. Refer to
Page 3 for proper DIP package pinout.)
–8– REV. D














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