High Common-Mode Voltage,
Programmable Gain Difference Amplifier
AD628
FEATURES
High common-mode input voltage range
鹵120 V at V
S
= 鹵15 V
Gain range 0.1 to 100
Operating temperature range: 鈭?0擄C to 鹵85擄C
Supply voltage range
Dual supply: 鹵2.25 V to 鹵18 V
Single supply: 4.5 V to 36 V
Excellent ac and dc performance
Offset temperature stability RTI: 10 渭V/擄C maximum
Offset: 鹵1.5 V mV maximum
CMRR RTI: 75 dB minimum, dc to 500 Hz, G = +1
FUNCTIONAL BLOCK DIAGRAM
R
EXT2
+V
S
R
EXT1
R
G
鈥揑N
100k惟
10k惟
G = +0.1
鈥揑N
A1
+IN
10k惟
鈥揑N
A2
+IN
OUT
+IN
100k惟
10k惟
AD628
C
FILT
CMRR (dB)
High voltage current shunt sensing
Programmable logic controllers
Analog input front end signal conditioning
+5 V, +10 V, 鹵5 V, 鹵10 V, and 4 to 20 mA
Isolation
Sensor signal conditioning
Power supply monitoring
Electrohydraulic control
Motor control
Figure 1.
130
120
110
100
90
80
70
60
50
40
10
100
1k
FREQUENCY (Hz)
10k
100k
02992-C-002
V
S
= 鹵15V
GENERAL DESCRIPTION
The AD628 is a precision difference amplifier that combines
excellent dc performance with high common-mode rejection
over a wide range of frequencies. When used to scale high
voltages, it allows simple conversion of standard control
voltages or currents for use with single-supply ADCs. A
wideband feedback loop minimizes distortion effects due to
capacitor charging of 危-螖 ADCs.
A reference pin (V
REF
) provides a dc offset for converting bipolar
to single-sided signals. The AD628 converts +5 V, +10 V, 鹵5 V,
鹵10 V, and 4 to 20 mA input signals to a single-ended output
within the input range of single-supply ADCs.
The AD628 has an input common-mode and differential-mode
operating range of 鹵120 V. The high common-mode input
impedance makes the device well suited for high voltage
measurements across a shunt resistor. The inverting input of the
buffer amplifier is available for making a remote Kelvin
connection.
V
S
= 鹵2.5V
30
Figure 2. CMRR vs. Frequency of the AD628
A precision 10 k惟 resistor connected to an external pin is
provided for either a low-pass filter or to attenuate large
differential input signals. A single capacitor implements a low-
pass filter. The AD628 operates from single and dual supplies
and is available in an 8-lead SOIC_N or 8-lead MSOP package.
It operates over the standard industrial temperature range of
鈭?0擄C to +85擄C.
Rev. F
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. Specifications subject to change without notice. No
license is granted by implication or otherwise under any patent or patent rights of Analog Devices.
Trademarks and registered trademarks are the property of their respective owners.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781.329.4700
www.analog.com
Fax: 781.461.3113
漏2006 Analog Devices, Inc. All rights reserved.
02992-C-001
APPLICATIONS
鈥揤
S
V
REF