AD628 Datasheet, PDF (1/20 Pages) Analog Devices – High Common-Mode Voltage Programmable Gain Difference Amplifier

High Common-Mode Voltage
Programmable Gain Difference Amplifier
AD628
FEATURES
High common-mode input voltage range
±120 V at VS = ±15 V
Gain range 0.1 to 100
Operating temperature range: −40°C to ±85°C
Supply voltage range
Dual supply: ±2.25 V to ±18 V
Single supply: 4.5 V to 36 V
Excellent ac and dc performance
Offset temperature stability RTI: 10 µV/°C max
Offset: ±1.5 V mV max
CMRR RTI: 75 dB min, dc to 500 Hz, G = +1
APPLICATIONS
High voltage current shunt sensing
Programmable logic controllers
Analog input front end signal conditioning
+5 V, +10 V, ±5 V, ±10 V and 4 to 20 mA
Isolation
Sensor signal conditioning
Power supply monitoring
Electrohydraulic control
Motor control
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 ∑-∆ ADCs.
A reference pin (VREF) provides a dc offset for converting
bipolar to single-sided signals. The AD628 converts +5 V, +10 V,
±5 V, ±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 ±120 V. The high common-mode
input impedance makes the device well suited for high voltage
measurements across a shunt resistor. The buffer amplifier’s
inverting input is available for making a remote Kelvin
connection.
FUNCTIONAL BLOCK DIAGRAM
R_EXT2
R_EXT1
+V_S
R_G
100kΩ
–IN
100kΩ
+IN
10kΩ
G = +0.1
–IN
A1
+IN
10kΩ
–V_S
V_REF
10kΩ
C_FILT
–IN
A2
+IN
OUT
AD628
Figure 1.
130
120
110
100
90
80
70
60
50
40
30
10
V_S = ±15V
V_S = ±2.5V
100
1k
10k
FREQUENCY (Hz)
100k
Figure 2. CMRR vs. Frequency of the AD628
A precision 10 kΩ 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 or MSOP package. It operates over
the standard industrial temperature range of −40°C to +85°C.
Rev. C
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