High Common-Mode Voltage,
Programmable Gain Difference Amplifier
FEATURES
High common-mode input voltage range
±120 V at 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 maximum
Offset: ±1.5 V mV maximum
CMRR RTI: 75 dB minimum, 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 controls
Motor controls
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 Σ- ADCs.
A reference pin (V
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 inverting input of
the buffer amplifier is available for making a remote Kelvin
connection.
= ±15 V
S
) provides a dc offset for converting bipolar
REF
AD628
FUNCTIONAL BLOCK DIAGRAM
EXT2
R
EXT1
R
G
67
–IN
+IN
AD628
VS = ±2.5V
A2
OUT
5
R
+V
S
–IN
+IN
100k
8
100k
1
10k
G = +0.1
–IN
A1
+IN
10k
2 3 4
–V
S
10k
V
REF
C
FILT
Figure 1.
130
120
110
100
90
80
CMRR (dB)
70
60
50
40
30
10010 1k 10k 100k
VS = ±15V
FREQUENCY (Hz)
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 lowpass filter. The AD628 operates from single and dual supplies
and is available in an 8-lead SOIC_N or an 8-lead MSOP. It
operates over the standard industrial temperature range of
−40°C to +85°C.
2992-001
02992-002
Rev. G
Information furnished by Analog Devices is believed to be accurate and reliable. However, no
responsibility is assumed by Anal og Devices for its use, nor for any infringements of patents or ot her
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 ©2002–2007 Analog Devices, Inc. All rights reserved.
AD628
TABLE OF CONTENTS
Features .............................................................................................. 1
Applications....................................................................................... 1
General Description......................................................................... 1
Functional Block Diagram .............................................................. 1
Revision History ............................................................................... 2
Specifications..................................................................................... 3
Absolute Maximum Ratings............................................................ 7
Thermal Characteristics .............................................................. 7
ESD Caution.................................................................................. 7
Pin Configuration and Function Descriptions............................. 8
Typical Performance Characteristics ............................................. 9
Test Cir c ui t s .....................................................................................13
REVISION HISTORY
4/07—Rev. F to Rev. G
Changes to Features.......................................................................... 1
Changes to Figure 22...................................................................... 11
Changes to Figure 25...................................................................... 13
Changes to Voltage Level Conversion Section............................ 17
Changes to Monitoring Battery Voltages Section ...................... 18
Changes to Figure 34...................................................................... 18
Changes to Figure 35...................................................................... 19
Updated Outline Dimensions....................................................... 20
3/06—Rev. E to Rev. F
Changes to Table 1............................................................................ 3
Changes to Figure 3.......................................................................... 7
Replaced Voltage Level Conversion Section ............................... 16
Changes to Figure 32 and Figure 33............................................. 17
Updated Outline Dimensions....................................................... 19
Changes to Ordering Guide.......................................................... 19
5/05—Rev. D to Rev. E
Changes to Table 1........................................................................... 3
Changes to Table 2........................................................................... 5
Changes to Figure 33.....................................................................18
3/05—Rev. C to Rev. D
Updated Format................................................................ Universal
Changes to Table 1........................................................................... 3
Changes to Table 2........................................................................... 5
4/04—Rev. B to Rev. C
Updated Format................................................................ Universal
Changes to Specifications............................................................... 3
Theory of Operation ...................................................................... 15
Applications Information.............................................................. 16
Gain Adjustment........................................................................ 16
Input Voltage Range................................................................... 16
Voltage Level Conversion.......................................................... 17
Current Loop Receiver .............................................................. 18
Monitoring Battery Voltages..................................................... 18
Filter Capacitor Values............................................................... 19
Kelvin Connection ..................................................................... 19
Outline Dimensions ....................................................................... 20
Ordering Guide .......................................................................... 20
Changes to Absolute Maximum Ratings...................................... 7
Changes to Figure 3......................................................................... 7
Changes to Figure 26.....................................................................13
Changes to Figure 27.....................................................................13
Changes to Theory of Operation................................................. 14
Changes to Figure 29.....................................................................14
Changes to Table 5.........................................................................15
Changes to Gain Adjustment Section......................................... 15
Added the Input Voltage Range Section..................................... 15
Added Figure 30 ............................................................................15
Added Figure 31 ............................................................................15
Changes to Voltage Level Conversion Section ..........................16
Changes to Figure 32.....................................................................16
Changes to Table 6.........................................................................16
Changes to Figure 33 and Figure 34............................................ 17
Changes to Figure 35.....................................................................18
Changes to Kelvin Connection Section...................................... 18
6/03—Rev. A to Rev. B
Changes to General Description ...................................................1
Changes to Specifications............................................................... 2
Changes to Ordering Guide........................................................... 4
Changes to TPCs 4, 5, and 6 .......................................................... 5
Changes to TPC 9............................................................................ 6
Updated Outline Dimensions...................................................... 14
1/03—Rev. 0 to Rev. A
Change to Ordering Guide............................................................. 4
11/02—Rev. 0: Initial Version
Rev. G | Page 2 of 20
AD628
SPECIFICATIONS
TA = 25°C, VS = ±15 V, RL = 2 kΩ, R
Table 1.
AD628AR AD628ARM
Parameter Conditions Min Typ Max Min Typ Max Unit
DIFFERENTIAL AND OUTPUT AMPLIFIER
Gain Equation G = +0.1 (1 + R
Gain Range See Figure 29 0.11 100 0.11 100 V/V
Offset Voltage
vs. Temperature 4 8 4 8 μV/°C
3
CMRR
500 Hz 75 75 dB
Minimum CMRR Over Temperature −40°C to +85°C 70 70 dB
vs. Temperature 1 4 1 4 (μV/V)/°C
PSRR (RTI) VS = ±10 V to ±18 V 77 94 77 94 dB
Input Voltage Range
Common Mode −120 +120 −120 +120 V
Differential −120 +120 −120 +120 V
Dynamic Response
Small Signal Bandwidth −3 dB G = +0.1 600 600 kHz
Full Power Bandwidth 5 5 kHz
Settling Time G = +0.1, to 0.01%, 100 V step 40 40 μs
Slew Rate 0.3 0.3 V/μs
Noise (RTI)
Spectral Density 1 kHz 300 300 nV/√Hz
0.1 Hz to 10 Hz 15 15 μV p-p
DIFFERENTIAL AMPLIFIER
Gain 0.1 0.1 V/V
Error −0.1 +0.01 +0.1 −0.1 +0.01 +0.1 %
vs. Temperature 5 5 ppm/°C
Nonlinearity 5 5 ppm
vs. Temperature 3 10 3 10 ppm
Offset Voltage RTI of input pins −1.5 +1.5 −1.5 +1.5 mV
vs. Temperature 8 8 μV/°C
Input Impedance
Differential 220 220 kΩ
Common Mode 55 55 kΩ
4
CMRR
500 Hz 75 75 dB
Minimum CMRR Over Temperature −40°C to +85°C 70 70 dB
vs. Temperature 1 4 1 4 (μV/V)/°C
Output Resistance 10 10 kΩ
Error −0.1 +0.1 −0.1 +0.1 %
= 10 kΩ, R
EXT1
V
EXT2
= 0 V; RTI of input pins2;
CM
output amplifier G = +1
RTI of input pins;
G = +0.1 to +100
RTI of input pins;
G = +0.1 to +100
= ∞, V
EXT1/REXT2
= 0 V, unless otherwise noted.
REF
) V/V
−1.5 +1.5 −1.5 +1.5 mV
75 75 dB
75 75 dB
Rev. G | Page 3 of 20
AD628
AD628AR AD628ARM
Parameter Conditions Min Typ Max Min Typ Max Unit
OUTPUT AMPLIFIER
Gain Equation G = (1 + R
Nonlinearity G = +1, V
EXT1/REXT2
OUT
Offset Voltage RTI of output amp −0.15 +0.15 −0.15 +0.15 mV
vs. Temperature 0.6 0.6 μV/°C
Output Voltage Swing RL = 10 kΩ −14.2 +14.1 −14.2 +14.1 V
R
= 2 kΩ −13.8 +13.6 −13.8 +13.6 V
L
Bias Current 1.5 3 1.5 3 nA
Offset Current 0.2 0.5 0.2 0.5 nA
CMRR VCM = ±13 V 130 130 dB
Open-Loop Gain V
= ±13 V 130 130 dB
OUT
POWER SUPPLY
Operating Range ±2.25 ±18 ±2.25 ±18 V
Quiescent Current 1.6 1.6 mA
TEMPERATURE RANGE −40 +85 −40 +85 °C
1
To use a lower gain, see the Ga section. in Adjustment
2
The addition of the difference amplifier and output amplifier offset voltage does not exceed this specification.
⎡
3
Error due to common mode as seen at the output:
4
Error due to common mode as seen at the output of A1:
OUT
⎢
=V
⎢
⎢
⎣
V
OUT
) V/V
= ±10 V 0.5 0.5 ppm
⎤
)(0.1)(
V
⎥
10
A1
CM
×
⎥
75
⎥
20
⎦
⎡
⎢
=
⎢
⎢
⎣
⎤
)(0.1)(
V
⎥
CM
.
⎥
75
⎥
20
10
⎦
][
GainAmplifierOutput
.
Rev. G | Page 4 of 20
AD628
TA = 25°C, VS = 5 V, RL = 2 kΩ, R
Table 2.
AD628AR AD628ARM
Parameter Conditions Min Typ Max Min Typ Max Unit
DIFFERENTIAL AND OUTPUT AMPLIFIER
Gain Equation G = +0.1(1+ R
Gain Range See Figure 29 0.11 100 0.11 100 V/V
Offset Voltage
vs. Temperature 6 15 6 15 μV/°C
3
CMRR
500 Hz 75 75 dB
Minimum CMRR Over Temperature −40°C to +85°C 70 70 dB
vs. Temperature 1 4 1 4 (μV/V)/°C
PSRR (RTI) VS = 4.5 V to 10 V 77 94 77 94 dB
Input Voltage Range
Common Mode
4
Differential −15 +15 −15 +15 V
Dynamic Response
Small Signal Bandwidth – 3 dB G = +0.1 440 440 kHz
Full Power Bandwidth 30 30 kHz
Settling Time G = +0.1; to 0.01%, 30 V step 15 15 μs
Slew Rate 0.3 0.3 V/μs
Noise (RTI)
Spectral Density 1 kHz 350 350 nV/√Hz
0.1 Hz to 10 Hz 15 15 μV p-p
DIFFERENTIAL AMPLIFIER
Gain 0.1 0.1 V/V
Error –0.1 +0.01 +0.1 –0.1 +0.01 +0.1 %
Nonlinearity 3 3 ppm
vs. Temperature 3 10 3 10 ppm
Offset Voltage RTI of input pins −2.5 +2.5 −2.5 +2.5 mV
vs. Temperature 10 10 μV/°C
Input Impedance
Differential 220 220 kΩ
Common Mode 55 55 kΩ
5
CMRR
500 Hz 75 75 dB
Minimum CMRR Over Temperature −40°C to +85°C 70 70 dB
vs. Temperature 1 4 1 4 (μV/V)/°C
Output Resistance 10 10 kΩ
Error −0.1 +0.1 −0.1 +0.1 %
OUTPUT AMPLIFIER
Gain Equation G = (1 + R
Nonlinearity G = +1, V
Output Offset Voltage RTI of output amplifier −0.15 +0.15 −0.15 +0.15 mV
vs. Temperature 0.6 0.6 μV/°C
Output Voltage Swing RL = 10 kΩ 0.9 4.1 0.9 4.1 V
R
Bias Current 1.5 3 1.5 3 nA
Offset Current 0.2 0.5 0.2 0.5 nA
CMRR VCM = 1 V to 4 V 130 130 dB
Open-Loop Gain V
= 10 kΩ, R
EXT1
= ∞, V
EXT2
= 2.25 V; RTI of input pins2;
V
CM
= 2.5 V, unless otherwise noted.
REF
EXT1/REXT2
) V/V
−3.0 +3.0 −3.0 +3.0 mV
output amplifier G = +1
RTI of input pins; G = +0.1 to +100 75 75 dB
−12 +17 −12 +17 V
RTI of input pins; G = +0.1 to +100 75 75 dB
EXT1/REXT2
OUT
= 2 kΩ 1 4 1 4 V
L
= 1 V to 4 V 130 130 dB
OUT
) V/V
= 1 V to 4 V 0.5 0.5 ppm
Rev. G | Page 5 of 20
AD628
AD628AR AD628ARM
Parameter Conditions Min Typ Max Min Typ Max Unit
POWER SUPPLY
Operating Range ±2.25 +36 ±2.25 +36 V
Quiescent Current 1.6 1.6 mA
TEMPERATURE RANGE −40 +85 −40 +85 °C
1
To use a lower gain, see the Gain Adjustment section.
2
The addition of the difference amplifier and output amplifier offset voltage does not exceed this specification.
10
A1
⎤
)(0.1)(
V
⎥
CM
×
⎥
75
⎥
20
⎦
.
REF
⎡
⎢
=
⎢
⎢
⎣
⎤
)(0.1)(
V
⎥
CM
.
⎥
75
⎥
20
10
⎦
GainAmplifierOutput
⎡
3
Error due to common mode as seen at the output: ][
4
Greater values of voltage are possible with greater or lesser values of V
5
Error due to common mode as seen at the output of A1:
⎢
V .
=
OUT
⎢
⎢
⎣
V
OUT
Rev. G | Page 6 of 20
Loading...