ANALOG DEVICES AD8222 Service Manual
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Precision, Dual-Channel
FEATURES
Two channels in small 4 mm × 4 mm LFCSP
Gain set with 1 resistor per amplifier (G = 1 to 10,000)
Low noise
8 nV/√Hz @ 1 kHz
0.25 μV p-p (0.1 Hz to 10 Hz)
High accuracy dc performance (B grade)
60 μV maximum input offset voltage
0.3 μV/°C maximum input offset drift
1.0 nA maximum input bias current
126 dB minimum CMRR (G = 100)
Excellent ac performance
150 kHz bandwidth (G = 100)
13 μs settling time to 0.001%
Differential output option (single channel)
Fully specified
Adjustable common-mode output
Supply range: ±2.3 V to ±18 V
APPLICATIONS
Multichannel data acquisition for
ECG and medical instrumentation
Industrial process controls
Wheatstone bridge sensors
Differential drives for
High resolution input ADCs
Remote sensors
GENERAL DESCRIPTION
The AD8222 is a dual-channel, high performance instrumentation
amplifier that requires only one external resistor per amplifier
to set gains of 1 to 10,000.
The AD8222 is the first dual-instrumentation amplifier in the
small 4 mm × 4mm LFCSP. It requires the same board area as a
typical single instrumentation amplifier. The smaller package
allows a 2× increase in channel density and a lower cost per
channel, all with no compromise in performance.
The AD8222 can also be configured as a single-channel,
differential output instrumentation amplifier. Differential
outputs provide high noise immunity, which can be useful when
the output signal must travel through a noisy environment, such
as with remote sensors. The configuration can also be used to
drive differential input ADCs.
Instrumentation Amplifier
AD8222
FUNCTIONAL BLOCK DIAGRAM
+VSOUT1
AD8222
1
–IN1
2
RG1
3
RG1
4
+IN1
5678
S
+V
Figure 1. 4mm × 4 mm LFCSP
Table 1. In Amps and Differential Amplifier by Category
High
Performance
AD8221
1
AD8220
AD8222
1
Rail-to-rail output.
Low
Cost
AD8553
AD6231
1
High
Voltage
AD628
AD629
The AD8222 maintains a minimum CMRR of 80 dB to 4 kHz
for all grades at G = 1. High CMRR over frequency allows the
AD8222 to reject wideband interference and line harmonics,
greatly simplifying filter requirements. The AD8222 also has a
typical CMRR drift over temperature of just 0.07 µV/V/°C at G = 1.
The AD8222 operates on both single and dual supplies and only
requires 2.2 mA maximum supply current for both amplifiers. It
is specified over the industrial temperature range of −40°C to
+85°C and is fully RoHS compliant.
For a single-channel version, see the AD8221.
S
OUT2
–V
13141516
12
–IN2
11
RG2
10
RG2
9
+IN2
S
–V
REF1
REF2
05947-001
Digital
1
Prog
Gain
AD8555
AD8556
AD8557
Mil
Grade
AD620
AD621
AD524
Low
Power
AD627
AD526
AD624
1
1
1
Rev. 0
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 ©2006 Analog Devices, Inc. All rights reserved.
AD8222
TABLE OF CONTENTS
Features .............................................................................................. 1
Layout .......................................................................................... 16
Applications....................................................................................... 1
Functional Block Diagram .............................................................. 1
General Description......................................................................... 1
Revision History ............................................................................... 2
Specifications..................................................................................... 3
Absolute Maximum Ratings............................................................ 6
Thermal Resistance ...................................................................... 6
ESD Caution.................................................................................. 6
Pin Configuration and Function Descriptions............................. 7
Typical Performance Characteristics ............................................. 8
Theory of Operation ...................................................................... 15
Amplifier Architecture .............................................................. 15
Gain Selection ............................................................................. 15
Reference Terminal ....................................................................16
Solder Wash................................................................................. 17
Input Bias Current Return Path ............................................... 17
Input Protection ......................................................................... 17
RF Interference........................................................................... 18
Common-Mode Input Voltage Range..................................... 18
Applications..................................................................................... 19
Differential Output .................................................................... 19
Driving a Differential Input ADC............................................ 20
Precision Strain Gauge .............................................................. 20
Driving Cabling.......................................................................... 21
Outline Dimensions ....................................................................... 22
Ordering Guide .......................................................................... 22
REVISION HISTORY
7/06—Revision 0: Initial Version
Rev. 0 | Page 2 of 24
AD8222
SPECIFICATIONS
VS = ±15 V, V
Table 2. Single-Ended and Differential
A Grade B Grade
Parameter Conditions Min Typ Max Min Typ Max Unit
COMMON-MODE REJECTION
RATIO (CMRR)
CMRR DC to 60 Hz 1 kΩ source imbalance
G = 1 80 86 dB
G = 10 100 106 dB
G = 100 120 126 dB
G = 1000 130 140 dB
CMRR at 4 kHz
G = 1 80 80 dB
G = 10 90 100 dB
G = 100 100 110 dB
G = 1000 100 110 dB
CMRR Drift T = −40°C to +85°C, G = 1 0.07 0.07 μV/V/°C
NOISE
Voltage Noise, 1 kHz RTI Noise = √(e
Input Voltage Noise, e
Output Voltage Noise, e
RTI f = 0.1 Hz to 10 Hz
G = 1 2 2 μV p-p
G = 10 0.5 0.5 μV p-p
G = 100 to 1000 0.25 0.25 μV p-p
Current Noise f = 1 kHz 40 40 fA/√Hz
f = 0.1 Hz to 10 Hz 6 6 pA p-p
VOLTAGE OFFSET RTI VOS = (V
Input Offset, V
Overtemperature T = −40°C to +85°C 150 80 μV
Average TC 0.4 0.3 μV/°C
Output Offset, V
Overtemperature T = −40°C to +85°C 0.8 0.5 mV
Average TC 9 5 μV/°C
Offset RTI vs. Supply (PSR) VS = ±2.3 V to ±18 V
G = 1 90 110 94 110 dB
G = 10 110 120 114 130 dB
G = 100 124 130 130 140 dB
G = 1000 130 140 140 150 dB
INPUT CURRENT (PER CHANNEL)
Input Bias Current 0.5 2.0 0.2 1.0 nA
Over temperature T = −40°C to +85°C 3.0 1.5 nA
Average TC 1 1 pA/°C
Input Offset Current 0.2 1 0.1 0.5 nA
Overtemperature T = −40°C to +85°C 1.5 0.6 nA
Average TC 1 0.5 2 pA/°C
REFERENCE INPUT
R
IN
I
IN
Voltage Range −V
Gain to Output
= 0 V, TA = 25°C, G = 1, RL = 2 kΩ, unless otherwise noted.
REF
1
Output Configuration
= –10 V to +10 V
V
CM
2
+ (eNO/G)2)
NI
V
, V
, V
NI
NO
OSI
OSO
IN+
V
, V
IN+
VS = ±5 V to ±15 V 120 60 μV
VS = ±5 V to ±15 V 500 350 μV
= 0 V 8 8 nV/√Hz
IN−
REF
, V
= 0 V 75 75 nV/√Hz
IN−
REF
OSI
) + (V
/G)
OSO
20 20 kΩ
V
, V
, V
IN+
= 0 V 50 60 50 60 μA
IN−
REF
S
+V
S
−V
S
1 ± 0.0001 1 ± 0.0001
+V
S
V
V/V
Rev. 0 | Page 3 of 24
AD8222
A Grade B Grade
Parameter Conditions Min Typ Max Min Typ Max Unit
GAIN G = 1 + (49.4 kΩ/RG)
Gain Range 1 10000 1 10000 V/V
Gain Error V
G = 1 0.05 0.02 %
G = 10 0.3 0.15 %
G = 100 0.3 0.15 %
G = 1000 0.3 0.15 %
Gain Nonlinearity V
G = 1 3 10 1 5 ppm
G = 10 7 20 7 20 ppm
G = 100 7 20 7 20 ppm
Gain vs. Temperature
G = 1 3 10 2 5 ppm/°C
2
G > 1
INPUT
Input Impedance
Differential 100||2 100||2 GΩ||pF
Common Mode 100||2 100||2 GΩ||pF
Input Operating Voltage Range3VS = ±2.3 V to ±5 V −VS + 1.9 +VS − 1.1 −VS + 1.9 +VS − 1.1 V
Overtemperature T = −40°C to +85°C −VS + 2.0 +VS − 1.2 −VS + 2.0 +VS − 1.2 V
Input Operating Voltage Range3VS = ±5 V to ±18 V −VS + 1.9 +VS − 1.2 −VS + 1.9 +VS − 1.2 V
Overtemperature T = −40°C to +85°C −VS + 2.0 +VS − 1.2 −VS + 2.0 +VS − 1.2 V
OUTPUT RL = 10 kΩ
Output Swing VS = ±2.3 V to ±5 V −VS + 1.1 +VS − 1.2 −VS + 1.1 +VS − 1.2 V
Overtemperature T = −40°C to +85°C −VS + 1.4 +VS − 1.3 −VS + 1.4 +VS − 1.3 V
Output Swing VS = ±5 V to ±18 V −VS + 1.2 +VS − 1.4 −VS + 1.2 +VS − 1.4 V
Overtemperature T = −40°C to +85°C −VS + 1.6 +VS − 1.5 −VS + 1.6 +VS − 1.5 V
Short-Circuit Current 18 18 mA
POWER SUPPLY
Operating Range VS = ±2.3 V to ±18 V ±2.3 ±18 ±2.3 ±18 V
Quiescent Current (per Amplifier) 0.9 1.1 0.9 1.1 mA
Overtemperature T = −40°C to +85°C 1 1.2 1 1.2 mA
TEMPERATURE RANGE
Specified Performance −40 +85 −40 +85 °C
Operational
1
Refers to differential configuration shown in Figure 49.
2
Does not include the effects of external resistor RG.
3
One input grounded. G = 1.
4
See Typical Performance Characteristics for expected operation between 85°C to 125°C.
4
± 10 V
OUT
= –10 V to +10 V
OUT
−50 −50 ppm/°C
−40 +125 −40 +125 °C
Rev. 0 | Page 4 of 24
AD8222
VS = ±15 V, V
Table 3. Single-Ended Output Configuration—Dynamic Performance (Both Amplifiers)
A Grade B Grade
Parameter Conditions Min Typ Max Min Typ Max Unit
DYNAMIC RESPONSE
Small Signal −3 dB Bandwidth
G = 1 1200 1200 kHz
G = 10 750 750 kHz
G = 100 140 140 kHz
G =1000 15 15 kHz
Settling Time 0.01% 10 V step
G = 1 to 100 10 10 μs
G = 1000 80 80 μs
Settling Time 0.001% 10 V step
G = 1 to 100 13 13 μs
G = 1000 110 110 μs
Slew Rate
G = 1 1.5 2 1.5 2 V/μs
G = 5 to 1000 2 2.5 2 2.5 V/μs
Table 4. Differential Output Configuration
A Grade B Grade
Parameter Conditions Min Typ Max Min Typ Max Unit
DYNAMIC RESPONSE
Small Signal −3 dB Bandwidth
G = 1 1000 1000 kHz
G = 10 650 650 kHz
G = 100 140 140 kHz
G =1000 15 15 kHz
Settling Time 0.01% 10 V step
G = 1 to 100 15 15 μs
G = 1000 80 80 μs
Settling Time 0.001% 10 V step
G = 1 to 100 18 18 μs
G = 1000 110 110 μs
Slew Rate
G = 1 1.5 2 1.5 2 V/μs
G = 5 to 1000 2 2.5 2 2.5 V/μs
1
Refers to differential configuration shown in Figure 49.
= 0 V, TA = 25°C, RL = 2 kΩ, unless otherwise noted.
REF
1
—Dynamic Performance
Rev. 0 | Page 5 of 24
AD8222
ABSOLUTE MAXIMUM RATINGS
Table 5.
Parameter Rating
Supply Voltage ±18 V
Output Short-Circuit Current Indefinite
Input Voltage (Common Mode) ±V
Differential Input Voltage ±V
Storage Temperature Range −65°C to +130°C
Operational Temperature Range −40°C to +125°C
Package Glass Transition Temperature (TG) 130°C
ESD (Human Body Model) 1 kV
ESD (Charge Device Model) 1 kV
S
S
Stresses above those listed under Absolute Maximum Ratings
may cause permanent damage to the device. This is a stress
rating only; functional operation of the device at these or any
other conditions above those indicated in the operational
section of this specification is not implied. Exposure to absolute
maximum rating conditions may affect device reliability.
THERMAL RESISTANCE
Table 6.
Thermal Pad θ
Soldered to Board 48 °C/W
Not Soldered to Board 86 °C/W
JA
The θJA values in Tabl e 6 assume a 4-layer JEDEC standard
board. If the thermal pad is soldered to the board, then it is
also assumed it is connected to a plane. θ
at the exposed pad
JC
is 4.4°C/W.
Maximum Power Dissipation
The maximum safe power dissipation for the AD8222 is limited
by the associated rise in junction temperature (T
approximately 130°C, which is the glass transition temperature,
the plastic changes its properties. Even temporarily exceeding
this temperature limit may change the stresses that the package
exerts on the die, permanently shifting the parametric performance
of the amplifiers. Exceeding a temperature of 130°C for an
extended period can result in a loss of functionality.
Unit
) on the die. At
J
ESD 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 this product 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.
Rev. 0 | Page 6 of 24
AD8222
PIN CONFIGURATION AND FUNCTION DESCRIPTIONS
S
+VSOUT1
OUT2
–V
161514
13
–IN1 1
RG1 2
RG1 3
+IN1 4
PIN 1
INDICATO R
AD8222
TOP VIEW
5
S
+V
REF1 6
12
–IN2
11
RG2
RG2
10
+IN2
9
8
S
–V
REF2 7
05947-002
Figure 2. Pin Configuration
Table 7. Pin Function Descriptions
Pin No Mnemonic Description
1 −IN1 Negative Input In-Amp 1
2 RG1 Gain Resistor In-Amp 1
3 RG1 Gain Resistor In-Amp 1
4 +IN1 Positive Input In-Amp 1
5 +V
S
Positive Supply
6 REF1 Reference Adjust In-Amp 1
7 REF2 Reference Adjust In-Amp 2
8 −V
S
Negative Supply
9 +IN2 Positive Input In-Amp 2
10 RG2 Gain Resistor In-Amp 2
11 RG2 Gain Resistor In-Amp 2
12 −IN2 Negative Input In-Amp 2
13 −V
S
Negative Supply
14 OUT2 Output In-Amp 2
15 OUT1 Output In-Amp 1
16 +V
S
Positive Supply
Rev. 0 | Page 7 of 24
AD8222
TYPICAL PERFORMANCE CHARACTERISTICS
500
400
300
N = 1713
800
600
200
NUMBER OF UNITS
100
0
–50 50403020100–10–20–30–40
CMRR (µV/V)
Figure 3. Typical Distribution for CMRR (G = 1)
300
250
200
150
NUMBER OF UNITS
100
10
0
–100 10080604020020406080
V
(µV)
OSI
Figure 4. Typical Distribution of Input Offset Voltage
700
600
500
N = 1713
N = 1713
400
NUMBER OF UNITS
200
0
–2.0 2.01. 51. 00.50–0.5–1.0–1.5
05947-003
I
OFFSET
(nA)
05947-006
Figure 6. Typical Distribution of Input Offset Current
15
10
= ±15V
V
VS = ±5V
S
05947-007
5
0
–5
–10
INPUT COMMON-MODE VOL TAGE (V)
–15
05947-004
–15 –10 –5 0 5 10 15
OUTPUT VOLTAGE (V)
Figure 7. Input Common-Mode Range vs. Output Voltage, G = 1
15
10
= ±15V
V
5
S
400
300
NUMBER OF UNITS
200
100
0
–2.0 2.01. 51. 00.50–0.5–1.0–1.5
I
BIAS
(nA)
Figure 5. Typical Distribution of Input Bias Current
05947-005
Rev. 0 | Page 8 of 24
0
–5
–10
INPUT COMMON-MODE VOL TAGE (V)
–15
–15 –10 –5 0 5 10 15
OUTPUT VOLTAGE (V)
VS = ±5V
Figure 8. Input Common-Mode Range vs. Output Voltage, G = 100
05947-008
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