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AD628 d
Datasheet
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Analog Devices AD628 d Datasheet

High Common-Mode Voltage
+IN–
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 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 Σ-Δ ADCs.
A reference pin (V 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 single­ended 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.
= ±15 V
S
) provides a dc offset for converting
REF
AD628

FUNCTIONAL BLOCK DIAGRAM

R
+V
S
100kΩ
IN
100kΩ
–V
10kΩ
G = +0.1
–IN
A1
+IN
10kΩ
V
S
REF
10kΩ
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 or MSOP package. It operates over the standard industrial temperature range of −40°C to +85°C.
EXT2
R
VS = ±2.5V
R
EXT1
G
–IN
+IN
AD628
A2
OUT
02992-C-001
02992-C-002
Rev. D
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 Fax: 781.461.3113
www.analog.com
©2005 Analog Devices, Inc. All rights reserved.
AD628

TABLE OF CONTENTS

Specifications..................................................................................... 3

REVISION HISTORY

Absolute Maximum Ratings............................................................ 7
ESD Caution.................................................................................. 7
Pin Configuration and Function Descriptions............................. 8
Typical Performance Characteristics ............................................. 9
Test C ir c uits ..................................................................................... 13
Theory of Operation ...................................................................... 15
Applications..................................................................................... 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
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
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. D | 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 AMP + OUTPUT AMP
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 BW –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 AMP
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
OCM
EXT2
= ∞, V
= 0, unless otherwise noted.
REF
EXT1/REXT2
) V/V
= 0 V; RTI of input pins2;
−1.5 +1.5 −1.5 +1.5 mV
Output amp G = +1
RTI of input pins;
75 75 dB
G = +0.1 to +100
RTI of input pins;
75 75 dB
G = +0.1 to +100
Rev. D | 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 amp’s and output amp’s 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
[
10
V
OUT
) V/V
= ±10 V 0.5 0.5 ppm
)(0.1)(
V
A1 =
CM
×=V
75
20
V
)(0.1)(
CM
[
]
75
20
10
][]
GainAmplifierOutput
Rev. D | 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 AMP + OUTPUT AMP
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 BW –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 AMP
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 amp −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
OCM
= 2.5, unless otherwise noted.
REF
EXT1/REXT2
) V/V
−3.0 +3.0 −3.0 +3.0 mV
Output Amp 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. D | 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 amp’s and output amp’s offset voltage does not exceed this specification.
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:
OUT
V
)(0.1)(
CM
[
V
OUT
×=V
75
20
10
A1 =
.
REF
V
CM
[
75
20
10
)(0.1)(
]
GainAmplifierOutput
Rev. D | Page 6 of 20
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