AD22057R Analog Devices Inc, AD22057R Datasheet - Page 3

• Manufacturer Part Number: AD22057R
• Description: IC AMP DIFF SNGL-SUP 8SOIC
• Manufacturer: Analog Devices Inc
• Type: Sensor Interfacer

Specifications of AD22057R

• Rohs Status: RoHS non-compliant
• Input Type: Voltage
• Output Type: Analog
• Interface: Differential
• Current - Supply: 200µA
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (3.9mm Width)

ABSOLUTE MAXIMUM RATINGS*
Supply Voltage . . . . . . . . . . . . . . . . . . . . . . . . +3.0 V to +36 V
Peak Input Voltage (40 ms) . . . . . . . . . . . . . . . . . . . . . . +60 V
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-
REV. A
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 (V
in the presence of large common-mode voltages (V
the use of any other active components.
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 (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 k resistor, which is trimmed to
signal of interest (see Low-Pass Filtering section). The inclusion
of an additional resistive network allows the output of A1 to be
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.
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.
OFS
3% (R12 in Figure 2) to facilitate the low-pass filtering of the
(Pin 7 to Pin 2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . +20 V
IN+
IN–
DM
in Figure 3) can be accurately amplified and filtered
AD22057
Figure 2. Simplified Schematic
A1
+V
S
S
OFS A1
– 1 V).
A2
A2
CM
) without
OUT
GND
–3–
offset to an optional voltage of one half of that supplied to Pin 7;
in many cases this offset would be +V
(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
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 k to ground, 400 k between 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
variation in the gain; for example, in absorbing the scaling error
of a transducer.
20. (This gain is easily user-configurable—see Altering the
0.5%). In some cases, it may be desirable to provide for some
Plastic Mini-DIP Package
GND
–IN
A1
A2
1
2
3
4
(Not to Scale)
AD22057
TOP VIEW
(N-8)
PIN CONFIGURATIONS
8
7
6
5
+IN
OFFSET
+V
OUT
S
WARNING!
Plastic SOIC Package
GND
S
–IN
A1
A2
/2 by tying Pin 7 to +V
1
2
3
4
(Not to Scale)
ESD SENSITIVE DEVICE
(SO-8)
AD22057
TOP VIEW
AD22057
8
7
6
5
+IN
OFFSET
+V
OUT
S
S