Analog Devices AD22057 a Datasheet

Single-Supply Sensor

a

FEATURES
Gain of ⴛ20. Alterable from ⴛ1 to ⴛ160
Input CMR from Below Ground to 6ⴛ (VS – 1 V)
Output Span 20 mV to (V
1-, 2-, 3-Pole Low-Pass Filtering Available
Accurate Midscale Offset Capability
Differential Input Resistance 400 k⍀
Drives 1 k⍀ Load to +4 V Using V
Supply Voltage: +3.0 V to +36 V
Transient Spike Protection and RFI Filters Included
Peak Input Voltage (40 ms): 60 V
Reversed Supply Protection: –34 V
Operating Temperature Range: –40ⴗC to +125ⴗC

APPLICATIONS
Current Sensing
Motor Control
Interface for Pressure Transducers, Position Indicators,

Strain Gages, and Other Low Level Signal Sources

Accelerometers

– 0.2) V

S

= +5 V

S

Interface Amplifier

FUNCTIONAL BLOCK DIAGRAM

+V

IN+
IN–

AD22057

A1

S

OFS A1

A2

AD22057

A2

OUT

GND

GENERAL DESCRIPTION

The AD22057 is a single-supply difference amplifier for ampli­fying and low-pass filtering small differential voltages (typically
100 mV FS at a gain of 40) from sources having a large common­mode voltage.

Supply voltages from +3.0 V to +36 V can be used. The input
common-mode range extends from below ground to +24V using

+V

(CAR BATTERY)

S

CMOS DRIVER

CHASSIS

SOLENOID
LOAD

100mV

POWER
DARLINGTON

SINGLE-POLE LOW-PASS FILTERING, GAIN: 40

Figure 1. Typical Application Circuit for a Current Sensor Interface

a +5 V supply with excellent rejection of this common-mode
voltage. This is achieved by the use of a special resistive attenua­tor at the input, laser trimmed to a very high differential balance.

Provisions are included for optional low-pass filtering and gain
adjustment. An accurate midscale offset feature allows bipolar
signals to be amplified.

+5V

ANALOG OUTPUT
4V PER AMP

AD22057

C

200kV

CORNER FREQUENCY

= 0.796Hz-mF

ANALOG GROUND

REV. A

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
which 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: [phone] World Wide Web Site: http://www.analog.com
Fax: [phone] © Analog Devices, Inc., 1999

AD22057–SPECIFICATIONS

(TA = +25ⴗC, VS = +5 V, VCM = 0, RL = 10 k⍀ unless otherwise noted)

Parameter Comments Test Conditions Min Typ Max Units

INPUTS (PINS 1 AND 8)

+CMR Positive Common-Mode Range TA = T
CMR Negative Common-Mode Range T
CMRR

LF

CMRR

HF

R

INCM

R

MATCH

R

INDIFF

PREAMPLIFIER

G

CL

V

O

R

O

OUTPUT BUFFER

G

CL

V

O

R

O

OVERALL SYSTEM

G Gain
V

OS

Common-Mode Rejection Ratio f ≤ 10 Hz 80 90 dB
Common-Mode Rejection Ratio f = 1 kHz 80 90 dB
Common-Mode Input Resistance Pin 1 or Pin 8 to Pin 2 180 240 300 kΩ
Matching of Resistances ±0.5 %
Differential Input Resistance Pin 1 to Pin 8 280 400 kΩ

Closed-Loop Gain
Output Voltage Range (Pin 3) +0.01 +4.8 V
Output Resistance

Closed-Loop Gain
Output Voltage Range

1

2

1

3

R

Output Resistance (Pin 5) VO ≥ 0.1 V dc 2.0 Ω

1

Gain Drift T
Input Offset Voltage

4

VO ≥ 0.1 V dc 19.9 20.0 20.1 V/V

Offset Drift T

= T

A

LOAD

= T

A

= T

A

to T

MIN
MIN

MAX

to +85°C –1.0 V

+24 V

9.7 10.0 10.3 V/V
97 100 103 kΩ

≥ 10 kΩ 1.94 2.0 2.06 V/V

+0.02 +4.8 V

MIN

to T

MAX

–62.5 +62.5 ppm/°C
–1 0.03 1 mV

MIN

to T

MAX

–12.5 +12.5 µV/°C

OFS Midscale Offset (Pin 7) Scaling 0.49 0.50 0.51 V/V

Input Resistance Pin 7 to Pin 2 2.5 3.0 kΩ

I

OSC

BW

–3 dB

SR Slew Rate 0.2 V/µs
N

SD

PSR Power Supply Rejection V

V

OS

Short-Circuit Output Current 7 11 25 mA

T

= T

A

MIN

to T

MAX

527mA

–3 dB Bandwidth VO = +1 V dc 20 30 kHz
Noise Spectral Density

Input Offset Voltage

4

4

f = 100 Hz to 10 kHz 0.2 µV/√Hz

= 5 V, VO = 1 V to 4.2 V

S

V

= 24 V, VO = 1 V to 22 V

S

= T

T

A

MIN

to T

MAX

20.0 µV/V

G Gain 0.05 %/V

POWER SUPPLY

V

S

I

S

Operating Range TA = T
Quiescent Supply Range

5

TA = +25°C, VS = +5 V 200 500 µA

MIN

to T

MAX

3536V

TEMPERATURE RANGE

T

OP

Operating Temperature Range –40 +125 °C

PACKAGE Plastic Mini-DIP (N-8) AD22057N

Plastic SOIC (SO-8) AD22057R

NOTES

1

Specified for default mode i.e., with no external components. The overall gain is trimmed to ±0.5% while the individual gains of A1 and A2 may be subject to a
maximum ±3% tolerance. Note that the actual gain in a particular application can be modified by the use of external resistor networks.

2

The actual output resistance of A1 is only a few ohms, but access to this output, via Pin 3, is always through a 100 kΩ resistor, which is trimmed to ±3%.

3

For VCM ≤ 20 V. For VCM > 20 V, VOL ⯝ 1 mV/V × VCM.

4

Referred to the input (Pins 1 and 8).

5

With VDM = 0 V. Differential mode signals are referred to as VDM, while VCM refers to common-mode voltages.

Specifications subject to change without notice.

ORDERING GUIDE

Model Temperature Range Package Descriptions Package Options

AD22057N –40°C to +125°C Plastic DIP N-8
AD22057R –40°C to +125°C Plastic SOIC SO-8
AD22057R-Reel –40°C to +125°C Tape and Reel SO-8*

*Quantities must be in increments of 2,500 pieces each.

–2–

REV. A

AD22057

WARNING!

ESD SENSITIVE DEVICE

ABSOLUTE MAXIMUM RATINGS*

PIN CONFIGURATIONS

Supply Voltage . . . . . . . . . . . . . . . . . . . . . . . . +3.0 V to +36 V

Peak Input Voltage (40 ms) . . . . . . . . . . . . . . . . . . . . . . +60 V

(Pin 7 to Pin 2) . . . . . . . . . . . . . . . . . . . . . . . . . . . .+20 V

V

OFS

Plastic Mini-DIP Package

(N-8)

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.

–IN

GND

A1

1

2

AD22057

TOP VIEW

3

(Not to Scale)

4

8

+IN
OFFSET

7

+V

6

OUTA2

5

S

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.

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 sig­nals (V
in the presence of large common-mode voltages (V

in Figure 3) can be accurately amplified and filtered

DM

) without

CM

the use of any other active components.

+V

AD22057

S

OFS A1

A2

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 +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
×20. (This gain is easily user-configurable—see Altering the
Gain section for details.)

The dynamic properties of the AD22057 are optimized for inter­facing 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.

IN+
IN–

A1

A2

OUT

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.

Plastic SOIC Package

(SO-8)

–IN

GND

A1
A2

1

2

AD22057

TOP VIEW

3

(Not to Scale)

4

8

+IN

7

OFFSET

6

+V
OUT

5

S

S

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 toler­ated by the actual input to A1. As a result, the input common­mode range extends to 6× (V

– 1 V).

S

Two small filter capacitors (not shown in Figure 2) have been
included at the inputs of A1 to minimize the effects of any spuri­ous 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 kΩ resistor, 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

REV. A

–3–

APPLICATIONS

The AD22057 can be used wherever a high gain, single-supply
differencing amplifier is required, and where a finite input resis­tance (240 kΩ to ground, 400 kΩ between differential inputs)
can be tolerated. In particular, the ability to handle a common­mode input considerably larger than the supply voltage is fre­quently 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 de­fault 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.