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AD22057RZ-RL View Datasheet(PDF) - Analog Devices

Part Name
Description
View to exact match
AD22057RZ-RL
ADI
Analog Devices ADI
AD22057RZ-RL Datasheet PDF : 9 Pages
1 2 3 4 5 6 7 8 9
AD22057
ABSOLUTE MAXIMUM RATINGS*
Supply Voltage . . . . . . . . . . . . . . . . . . . . . . . . +3.0 V to +36 V
Peak Input Voltage (40 ms) . . . . . . . . . . . . . . . . . . . . . . +60 V
VOFS (Pin 7 to Pin 2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . +20 V
Reversed Supply Voltage Protection . . . . . . . . . . . . . . . –34 V
Operating Temperature . . . . . . . . . . . . . . . . –40°C to +125°C
Storage Temperature . . . . . . . . . . . . . . . . . . –65°C to +150°C
Output Short Circuit Duration . . . . . . . . . . . . . . . . Indefinite
Lead Temperature Range (Soldering 60 sec) . . . . . . . . +300°C
*Stresses above those listed under Absolute Maximum Ratings may cause perma-
nent damage to the device. This is a stress rating only; the functional operation of
the device at these or any other conditions above those indicated in the operational
sections of this specification is not implied. Exposure to absolute maximum rating
conditions for extended periods may affect device reliability.
PIN CONFIGURATION
Plastic SOIC Package
(R-8)
–IN 1
8 +IN
GND 2 AD22057 7 OFFSET
TOP VIEW
A1 3 (Not to Scale) 6 +VS
A2 4
5 OUT
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 AD22057 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
PRODUCT DESCRIPTION
The AD22057 is a single-supply difference amplifier consisting
of a precision balanced attenuator, a very low drift preamplifier
and an output buffer amplifier (A1 and A2, respectively, in
Figure 2). It has been designed so that small differential sig-
nals (VDM in Figure 3) can be accurately amplified and filtered
in the presence of large common-mode voltages (VCM) without
the use of any other active components.
+VS OFS A1 A2
AD22057
IN+
A1
IN–
A2
OUT
GND
Figure 2. Simplified Schematic
The resistive attenuator network is situated at the input to the
AD22057 (Pins 1 and 8), allowing the common-mode voltage at
Pins 1 and 8 to be six times greater than that which can be toler-
ated by the actual input to A1. As a result, the input common-
mode range extends to 6× (VS – 1 V).
Two small filter capacitors (not shown in Figure 2) have been
included at the inputs of A1 to minimize the effects of any spuri-
ous RF signals present in the signal.
Internal feedback around A1 sets the closed-loop gain of the
preamplifier to ×10 from the input pins; the output of A1 is
connected to Pin 3 via a 100 kresistor, which is trimmed to
± 3% (R12 in Figure 2) to facilitate the low-pass filtering of the
signal of interest (see Low-Pass Filtering section). The inclusion
of an additional resistive network allows the output of A1 to be
offset to an optional voltage of one half of that supplied to Pin 7;
in many cases this offset would be +VS/2 by tying Pin 7 to +VS
(Pin 6), permitting the conditioning and processing of bipolar
signals (see Strain Gage Interface section).
The output buffer A2 has a gain of ×2, setting the precalibrated,
overall gain of the AD22057, with no external components, to
×20. (This gain is easily user-configurable—see Altering the
Gain section for details.)
The dynamic properties of the AD22057 are optimized for inter-
facing to transducers; in particular, current sensing shunt
resistors. Its rejection of large, high frequency, common-mode
signals makes it superior to that of many alternative approaches.
This is due to the very careful design of the input attenuator and
the close integration of this highly balanced, high impedance
system with the preamplifier.
APPLICATIONS
The AD22057 can be used wherever a high gain, single-supply
differencing amplifier is required, and where a finite input resis-
tance (240 kto ground, 400 kbetween differential inputs)
can be tolerated. In particular, the ability to handle a common-
mode input considerably larger than the supply voltage is fre-
quently of value.
Also, the output can run down to within 20 mV of ground,
provided it is not called on to sink any load current. Finally, the
output can be offset to half of a full-scale reference voltage (with
a tolerance of ± 2%) to allow a bipolar input signal.
ALTERING THE GAIN
The gain of the preamplifier, from the attenuator input (Pins 1
and 8) to its output at Pin 3, is ×10 and that of the output
buffer, from Pin 4 to Pin 5, is ×2, thus making the overall de-
fault gain ×20. The overall gain is accurately trimmed (to within
± 0.5%). In some cases, it may be desirable to provide for some
variation in the gain; for example, in absorbing the scaling error
of a transducer.
REV. B
–3–
 

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