FEATURES
●LOW COST
●LOW QUIESCENT CURRENT:
40µA/channel
Shut Down: < 1µA
●HIGH GAIN ACCURACY:
G = 5, 0.07 %, 2ppm/°C
●GAIN SET WITH EXTERNAL RESISTORS
●LOW BIAS CURRENT: 10pA
●BANDWIDTH: 500kHz, G = 5V/V
●RAIL-TO-RAIL OUTPUT SWING: (V+) – 0.02V
●WIDE TEMPERATURE RANGE:
–55°C to +125°C
●SINGLE VERSION IN MSOP-8 PACKAGE AND
DUAL VERSION IN TSSOP-14 PACKAGE
micro
Power, Single-Supply, CMOS
INSTRUMENTATION AMPLIFIER
DESCRIPTION
The INA322 family is a series of low cost, rail-to-rail output,
micropower CMOS instrumentation amplifiers that offer wide-
range, single-supply, as well as bipolar-supply operation.
The INA322 family provides low-cost, low-noise amplification
of differential signals with micropower current consumption of
40µA. When shutdown the INA322 has a quiescent current
of less than 1µA. Returning to normal operations within
microseconds, the shutdown feature makes the INA322
optimal for low-power battery or multiplexing applications.
APPLICATIONS
● INDUSTRIAL SENSOR AMPLIFIERS:
Bridge, RTD, Thermistor, Position
● PHYSIOLOGICAL AMPLIFIERS:
ECG, EEG, EMG
● A/D CONVERTER SIGNAL CONDITIONING
● DIFFERENTIAL LINE RECEIVERS WITH GAIN
● FIELD UTILITY METERS
● PCMCIA CARDS
● COMMUNICATION SYSTEMS
● TEST EQUIPMENT
● AUTOMOTIVE INSTRUMENTATION
®
INA322
Configured internally for 5V/V gain, the INA322 offers excep-
tional flexibility with user-programmable external gain resis-
tors. The INA322 reduces common-mode error over fre-
quency and with CMRR remaining high up to 3kHz, line noise
and line harmonics are rejected.
The low-power design does not compromise on bandwidth or
slew rate, making the INA322 ideal for driving sampling Ana-
log-to-Digital (A/D) converters as well as general-purpose
applications. With high precision, low cost, and small packag-
ing, the INA322 outperforms discrete designs, while offering
reliability and performance.
A2
A1 A3
160kΩ
REF
V
IN–
V
IN+
40kΩ40kΩ
Shutdown V+
V
OUT
V
OUT
= (V
IN+
– V
IN–
) • Gain
Gain = 5 + 5(R2/R1)
V–
R
2
R
1
RG
160kΩ
INA322
INA2322
SBOS174B – DECEMBER 2000 – REVISED FEBRUARY 2006
www.ti.com
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of Texas Instruments
standard warranty. Production processing does not necessarily include
testing of all parameters.
Copyright © 2000-2006, Texas Instruments Incorporated
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of
Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
All trademarks are the property of their respective owners.
INA322
2
SBOS174B
Supply Voltage, V+ to V–................................................................... 7.5V
Signal Input Terminals, Voltage(2) .................. (V–) – 0.5V to (V+) + 0.5V
Current(2) .................................................... 10mA
Output Short-Circuit(3) .............................................................. Continuous
Operating Temperature ..................................................–65°C to +150°C
Storage Temperature .....................................................–65°C to +150°C
Junction Temperature.................................................................... +150°C
NOTE: (1) Stresses above these ratings may cause permanent damage.
Exposure to absolute maximum conditions for extended periods may degrade
device reliability. These are stress ratings only, and functional operation of the
device at these or any other conditions beyond those specified is not implied.
(2) Input terminals are diode-clamped to the power-supply rails. Input signals
that can swing more than 0.5V beyond the supply rails should be current limited
to 10mA or less. (3) Short-circuit to ground, one amplifier per package.
ABSOLUTE MAXIMUM RATINGS(1)
PIN CONFIGURATIONS
Top View
1
2
3
4
5
6
7
14
13
12
11
10
9
8
Shutdown A
V
OUT
A
REFA
V+
REFB
V
OUT
B
Shutdown B
RGA
V
IN
–A
V
IN
+A
V–
V
IN
+B
V
IN
–B
RGB
INA2322
Dual, TSSOP-14 (EA)
RG
V
IN
–
V
IN
+
V–
Shutdown
V+
V
OUT
REF
INA322
MSOP-8 (EA)
1
2
3
4
8
7
6
5
ELECTROSTATIC
DISCHARGE SENSITIVITY
This integrated circuit can be damaged by ESD. Texas Instru-
ments recommends that all integrated circuits be handled with
appropriate precautions. Failure to observe proper handling
and installation procedures can cause damage.
ESD damage can range from subtle performance degradation
to complete device failure. Precision integrated circuits may be
more susceptible to damage because very small parametric
changes could cause the device not to meet its published
specifications.
PACKAGE PACKAGE
PRODUCT PACKAGE-LEAD DESIGNATOR MARKING
SINGLE
INA322EA MSOP-8 DGK C22
DUAL
INA2322EA TSSOP-14 PW INA2322EA
NOTES: (1) For the most current package and ordering information, see the Package Option Addendum at the end of this document, or see the TI website at
www.ti.com.
PACKAGE/ORDERING INFORMATION(1)
INA322 3
SBOS174B
ELECTRICAL CHARACTERISTICS: VS = +2.7V TO +5.5V
BOLDFACE limits apply over the specified temperature range, TA = –55°C TO +125°C
At TA = +25°C, RL = 25kΩ, G = 25, and IA common = VS/2, unless otherwise noted.
INA322EA
INA2322EA
PARAMETER CONDITION MIN TYP MAX UNITS
INPUT
Input Offset Voltage, RTI VS = +5V ±2±10 mV
Over Temperature VOS ±11 mV
vs Temperature dVOS/dT ±7µV/°C
vs Power Supply PSRR VS = +2.7V to +5.5V ±50 ±250 µV/V
Over Temperature ±260 µV/V
Long-Term Stability ±0.4 µV/month
Input Impedance 1013 || 3 Ω || pF
Input Common-Mode Range VS = 2.7V 0.35 1.5 V
VS = 5V 0.55 3.8 V
Common-Mode Rejection CMRR VS = 5V, VCM = 0.55V to 3.8V 60 73 dB
Over Temperature VS = 5V, VCM = 0.55V to 3.8V 60 dB
VS = 2.7V, VCM = 0.35V to 1.5V 73 dB
Crosstalk, Dual 110 dB
INPUT BIAS CURRENT
Bias Current IB±0.5 ±10 pA
Offset Current IOS ±0.5 ±10 pA
NOISE, RTI enRS = 0Ω
Voltage Noise: f = 10Hz 500 nV/√Hz
f = 100Hz 190 nV/√Hz
f = 1kHz 100 nV/√Hz
f = 0.1Hz to 10Hz 20 µVp-p
Current Noise: f = 1kHz 3fA/√Hz
GAIN(1)
Gain Equation, Externally Set G > 5 G = 5 + 5(R2/R1)
Range of Gain 5 1000 V/V
Gain Error ±0.07 ±0.4 %
vs Temperature G = 5 ±2±10 ppm/°C
Nonlinearity
G = 25, V
S
= 5V, V
O
= 0.05 to 4.95
±0.001 ±0.010 % of FS
Over Temperature ±0.002 ±0.015 % of FS
OUTPUT
Output Voltage Swing from Rail(2, 5) G ≥ 10 50 25 mV
Over Temperature 50 mV
Capacitance Load Drive See Typical Characteristic(3) pF
Short-Circuit Current ISC–8
ISC+ 16 mA
FREQUENCY RESPONSE
Bandwidth, –3dB BW G = 5 500 kHz
Slew Rate SR VS = 5V, G = 25 0.4 V/µs
Settling Time, 0.1% tSG = 5, CL = 50pF, VO = 2V step 8 µs
0.01% 12 µs
Overload Recovery 50% Input Overload G = 25 2 µs
POWER SUPPLY
Specified Voltage Range +2.7 +5.5 V
Operating Voltage Range
+2.5 to +5.5
V
Quiescent Current per Channel IQVSD > 2.5(4) 40 60 µA
Over Temperature 70 µA
Shutdown Quiescent Current/Chan ISD VSD < 0.8(4) 0.01 1 µA
TEMPERATURE RANGE
Specified Range –55 +125 °C
Operating/Storage Range –65 +150 °C
Thermal Resistance
θ
JA
MSOP-8, TSSOP-14 Surface Mount
150 °C/W
NOTES: (1) Does not include errors from external gain setting resistors (2) Output voltage swings are measured between the output and power-supply rails. Output
swings and rail only if G ≥ 10. (3) See typical characteristic
Percent Overshoot vs Load Capacitance
. (4) See typical characteristic
Shutdown Voltage vs Supply
Voltage
. (5) Output does not swing to positive rail if gain is less than 10.
INA322
4
SBOS174B
TYPICAL CHARACTERISTICS
At TA = +25°C, VS = 5V, VCM = 1/2 VS, RL = 25kΩ, CL = 50pF, unless otherwise noted.
GAIN vs FREQUENCY
10
Gain (dB)
Frequency (Hz)
100 1k 10k 100k 1M 10M
80
70
60
50
40
30
20
10
0
–10
–20
Gain = 500
Gain = 100
Gain = 25
Gain = 5
COMMON-MODE REJECTION RATIO
vs FREQUENCY
10
CMRR (dB)
Frequency (Hz)
100 1k 10k 100k
120
100
80
60
40
20
0
POWER-SUPPLY REJECTION RATIO
vs FREQUENCY
1
PSRR (dB)
Frequency (Hz)
10 100 1k 10k 100k
100
90
80
70
60
50
40
30
20
10
0
MAXIMUM OUTPUT VOLTAGE vs FREQUENCY
100
Maximum Output Voltage (Vp-p)
Frequency (Hz)
1k 10k 100k 1M 10M
6
5
4
3
2
1
0
V
S
= 5.5V
V
S
= 5.0V
V
S
= 2.7V
NOISE vs FREQUENCY
1
VNoise (nV/√Hz)
Frequency (Hz)
10 100 10k1k 100k
10k
1k
100
10
100
10
1
0.1
INoise (fA/√Hz)
0.1Hz TO 10Hz VOLTAGE NOISE
1s/div
10µv/div
INA322 5
SBOS174B
TYPICAL CHARACTERISTICS (Cont.)
At TA = +25°C, VS = 5V, VCM = 1/2 VS, RL = 25kΩ, CL = 50pF, unless otherwise noted.
To Positive Rail
To Negative Rail
OUTPUT SWING vs LOAD RESISTANCE
0
Swing to Rail (mV)
RLoad (Ω)
20k 40k 60k 80k 100k
25
20
15
10
5
0
COMMON-MODE INPUT RANGE
vs REFERENCE VOLTAGE
0
Output—Referred to Ground (V)
Input Common-Mode Voltage (V)
12345
6
5
4
3
2
1
0
Outside of Normal Operation
REF
Increasing
QUIESCENT CURRENT AND SHUTDOWN CURRENT
vs POWER SUPPLY
IQ (µA)
ISD (nA)
Supply Voltage (V)
2.5 3 3.5 4 4.5 55.5
50
45
40
35
30
25
20
15
10
5
0
500
450
400
350
300
250
200
150
100
50
0
IQ
ISD
QUIESCENT CURRENT AND SHUTDOWN CURRENT
vs TEMPERATURE
–75
I
Q
(µA)
600
500
400
300
200
100
0
I
SD
(nA)
Temperature (°C)
–50 –25 0 25 50 75 100 125 150
60
55
50
45
40
35
30
25
20
15
10
5
0
I
Q
I
SD
SHORT-CIRCUIT CURRENT vs POWER SUPPLY
ISC (mA)
Supply Voltage (V)
2.5 3 3.5 4 4.5 5 5.5
20
15
10
5
0
ISC+
ISC–
SHORT-CIRCUIT CURRENT vs TEMPERATURE
–75
I
SC
(mA)
Temperature (°C)
–50 –25 0 25 50 75 100 125 150
30
25
20
15
10
5
0
I
SC+
I
SC–
INA322
6
SBOS174B
TYPICAL CHARACTERISTICS (Cont.)
At TA = +25°C, VS = 5V, VCM = 1/2 VS, RL = 25kΩ, CL = 50pF, unless otherwise noted.
SMALL-SIGNAL STEP RESPONSE (G = 5)
10µs/div
100mv/div
SMALL-SIGNAL STEP RESPONSE (G = 100)
50µs/div
50mv/div
SMALL-SIGNAL STEP RESPONSE
(G = 5, CL = 1000pF)
10µs/div
100mv/div
SMALL-SIGNAL STEP RESPONSE
(G = 100, CL = 1000pF)
50µs/div
50mv/div
SMALL-SIGNAL STEP RESPONSE
(G = 100, CL = 5000pF)
50µs/div
50mv/div
50µs/div
1V/div
LARGE-SIGNAL STEP RESPONSE
(G = 25, CL = 50pF)
INA322 7
SBOS174B
TYPICAL CHARACTERISTICS (Cont.)
At TA = +25°C, VS = 5V, VCM = 1/2 VS, RL = 25kΩ, CL = 50pF, unless otherwise noted.
SETTLING TIME vs GAIN
1 10 100 1000
Gain (V/V)
Settling Time (µs)
100
90
80
70
60
50
40
30
20
10
0
Output 2Vp-p
Differential
Input Drive
0.01%
0.1%
PERCENT OVERSHOOT vs LOAD CAPACITANCE
10 100 1k 10k
Load Capacitance (pF)
Overshoot (%)
60
50
40
30
20
10
0
Output 100mVp-p
Differential
Input Drive G = 5
G = 25
SHUTDOWN VOLTAGE vs SUPPLY VOLTAGE
2.3
Shutdown (V)
Supply Voltage (V)
3 3.5 4 4.5 5 5.5
3
2.5
2
1.5
1
0.5
0
Normal Operation Mode
Part Draws Below 1µA Quiescent Current
Operation in this Region
is not Recommended
Shutdown Mode
SHUTDOWN TRANSIENT BEHAVIOR
50µs/div
1V/div
V
SD
V
OUT
20
18
16
14
12
10
8
6
4
2
0
–10
–9
–8
–7
–6
–5
–4
–3
–2
–1
0
1
2
3
4
5
6
7
8
9
10
Offset Voltage (mV)
Percentage of Amplifiers (%)
OFFSET VOLTAGE PRODUCTION DISTRIBUTION 20
18
16
14
12
10
8
6
4
2
0
–20
–18
–16
–14
–12
–10
–8
–6
–4
–2
0
2
4
6
8
10
12
14
16
18
20
Offset Voltage Drift (µV/°C)
Percentage of Amplifiers (%)
OFFSET VOLTAGE DRIFT
PRODUCTION DISTRIBUTION
INA322
8
SBOS174B
TYPICAL CHARACTERISTICS (Cont.)
At TA = +25°C, VS = 5V, VCM = 1/2 VS, RL = 25kΩ, CL = 50pF, unless otherwise noted.
SLEW RATE vs TEMPERATURE
–75
SR (V/µs)
Temperature (°C)
–50 –25 0 25 50 75 100 125 150
1
0.8
0.6
0.4
0.2
0
INPUT BIAS CURRENT vs TEMPERATURE
–75 –50 –25 0 25 50 75 100 125 150
Temperature (°C)
Input Bias Current (pA)
10k
1k
100
10
0
0.1
CROSSTALK vs FREQUENCY
0.1 1 10 100 1k 10k 100k 1M
Frequency (Hz)
Crosstalk (dB)
120
100
80
60
40
20
0
OUTPUT VOLTAGE SWING vs OUTPUT CURRENT
0 2 4 6 81012141618202224
Output Current (mA)
Output Voltage (V)
5
4
3
2
1
0
125°C25°C–55°C
125°C25°C–55°C
INA322 9
SBOS174B
APPLICATIONS INFORMATION
The INA322 is a modified version of the classic “two op amp”
instrumentation amplifier, with an additional gain amplifier.
Figure 1 shows the basic connections for the operation of the
INA322 and INA2322. The power supply should be capaci-
tively decoupled with 0.1µF capacitors as close to the
INA322 as possible for noisy or high-impedance applica-
tions.
The output is referred to the reference terminal, which must
be at least 1.2V below the positive supply rail.
OPERATING VOLTAGE
The INA322 family is fully specified over a supply range of
+2.7V to +5.5V, with key parameters specified over the
temperature range of -55°C to +125°C. Parameters that vary
significantly with operating conditions, such as load condi-
tions or temperature, are shown in the Typical Characteristic
Curves.
The INA322 may be operated on a single supply. Figure 2
shows a bridge amplifier circuit operated from a single +5V
supply. The bridge provides a small differential voltage
riding on an input common-mode voltage.
FIGURE 1. Basic Connections.
FIGURE 2. Bridge Amplifier of the INA322.
160kΩ40kΩ
40kΩ
160kΩ
3
2
5
1
78 4Also drawn in simplified form:
6
REF
0.1µF0.1µF
RG
V
IN
–
V
IN
+
V–
V+
A1 A3
A2
V
O
= ((V
IN
+) – (V
IN
–)) • G
Short V
OUT
to RG
for G = 5 5
10
50
100
SHORT
100kΩ
90kΩ
190kΩ
OPEN
100kΩ
10kΩ
10kΩ
R
2
R
1
Shutdown (For Single
Supply)
DESIRED GAIN
(V/V) R
1
R
2
G = 5 + 5(R
2
/ R
1
)
INA322
5
3
2
V
OUT
8
7
6
41
V+ Shutdown
RG
V
IN
–
V–
V
IN+
REF
Bridge
Sensor
+5V
NOTE: (1) REF should be adjusted for the desired output level,
keeping in mind that the value of REF affects the common-mode
input range. See Typical Characteristic Curves.
INA322
5
3
2
V
OUT
8
7
6
4
1
V+ Shutdown
RG
V
IN
–
V–
V
IN
+
REF
(1)
INA322
10
SBOS174B
SETTING THE GAIN
The ratio of R2 to R1, or the impedance between pins 1, 5,
and 6, determines the gain of the INA322. With an internally
set gain of 5, the INA322 can be programmed for gains
greater than 5 according to the following equation:
G = 5 + 5(R2/R1)
The INA322 is designed to provide accurate gain, with gain
error specified to be less than 0.4%. Setting gain with
matching TC resistors will minimize gain drift. Errors from
external resistors will add directly to the error, and may
become dominant error sources.
INPUT COMMON-MODE RANGE
The upper limit of the common mode input range is set by
the common-mode input range of the second amplifier, A2,
to 1.2V below positive supply. Under most conditions, the
amplifier operates beyond this point with reduced perfor-
mance. The lower limit of the input range is bounded by the
output swing of amplifier A1, and is a function of the
reference voltage according to the following equation:
VOA1 = 5/4 VCM – 1/4 VREF
(See Typical Characteristic Curves for Input Common-
Mode Range vs Reference Voltage).
REFERENCE
The reference terminal defines the zero output voltage level.
In setting the reference voltage, the common mode input of
A3 should be considered according to the following equa-
tion:
VOA2 = VREF + 5(VIN+ – VIN–)
VOA2 should be less than VDD – 1.2V.
The reference pin requires a low-impedance connection.
Any resistance in series with the reference pin will degrade
the CMRR. The reference pin may be used to compensate
for the offset voltage (see Offset Trimming section). The
reference voltage level also influences the common-mode
input range (see Common-Mode Input Range section).
INPUT BIAS CURRENT RETURN
With a high input impedance of 1013Ω, the INA322 is ideal
for use with high-impedance sources. The input bias current
of less than 10pA makes the INA322 nearly independent of
input impedance and ideal for low-power applications.
For proper operation, a path must be provided for input bias
currents for both inputs. Without input bias current paths,
the inputs will “float” to a potential that exceeds common-
FIGURE 3. Providing an Input Common-Mode Path.
mode range and the input amplifier will saturate. Figure 3
shows how bias current path can be provided in the cases of
microphone applications, thermistor applications, ground
returns, and dc-coupled resistive bridge applications.
When differential source impedance is low, the bias current
return path can be connected to one input. With higher
source impedance, two equal resistors will provide a bal-
anced input. The advantages are lower input offset voltage
due to bias current flowing through the source impedance
and better high-frequency gain.
Center-tap
provides bias
current return
Bridge resistance
provides bias
current return
Transformer
Bridge
Amplifier
Bridge
Sensor
VB(1)
VEX
NOTE: (1) VB is bias voltage within
common-mode range, dependent
on REF.
INA322
5
3
2
8
7
6
41
V+ Shutdown
VIN–
V–
VIN+
REF
INA322
5
3
2
8
7
6
41
V+ Shutdown
VIN–
V–
VIN+
REF
47kΩ
Microphone,
Hydrophone,
etc.
VB(1)
INA322
5
3
2
8
7
6
41
V+ Shutdown
VIN–
V–
VIN+
REF VOUT
RG
VOUT
RG
VOUT
RG
INA322 11
SBOS174B
SHUTDOWN MODE
The shutdown pin of the INA322 is nominally connected to
V+. When the pin is pulled below 0.8V on a 5V supply, the
INA322 goes into sleep mode within nanoseconds.
For actual shutdown threshold, see typical characteristic curve
“Shutdown Voltage vs Supply Voltage”. Drawing less than
1µA of current, and returning from sleep mode in microsec-
onds, the shutdown feature is useful for portable applications.
Once in ‘sleep-mode’ the amplifier has high output imped-
ance, making the INA322 suitable for multiplexing.
RAIL-TO-RAIL OUTPUT
A class AB output stage with common-source transistors is
used to achieve rail-to-rail output for gains of 10 or greater.
When the amplifier is in G = 5 the output will not swing to
positive rail. For resistive loads greater than 25kΩ, the
output voltage can swing to within a few millivolts of the
supply rail while maintaining low gain error. For heavier
loads and over temperature, see the typical characteristic
curve “Output Voltage Swing vs Output Current.” The
INA322’s low output impedance at high frequencies makes
it suitable for directly driving Capacitive Digital-to-Analog
(CDAC) input A/D converters, as shown in Figure 5.
OUTPUT BUFFERING
The INA322 is optimized for a load impedance of 10kΩ or
greater. For higher output current the INA322 can be buff-
ered using the OPA340, as shown in Figure 4. The OPA340
can swing within 50mV of the supply rail, driving a 600Ω
load. The OPA340 is available in the tiny MSOP-8 package.
OFFSET TRIMMING
In the event that external offset adjustment is required, the
offset can be adjusted by applying a correction voltage to the
reference terminal. Figure 6 shows an optional circuit for
trimming offset voltage. The voltage applied to the REF
terminal is added to the output signal. The gain from REF to
VOUT is +1. An op-amp buffer is used to provide low
impedance at the REF terminal to preserve good common-
mode rejection.
FIGURE 4. Output Buffering Circuit. Able to drive loads
as low as 600Ω.
INPUT PROTECTION
Device inputs are protected by ESD diodes that will conduct
if the input voltages exceed the power supplies by more than
500mV. Momentary voltages greater than 500mV beyond
the power supply can be tolerated if the current through the
input pins is limited to 10mA. This is easily accomplished
with input resistor RLIM, as shown in Figure 7. Many input
signals are inherently current-limited to less than 10mA,
therefore, a limiting resistor is not required.
FIGURE 6. Optional Offset Trimming Voltage.
FIGURE 5. INA322 Directly Drives a Capacitive-Input,
A/D Converter. FIGURE 7. Input Protection.
OPA340 V
OUT
+5V
0.1µF
0.1µF
INA322
5
3
2
V
OUT
8
7
6
41
V+ Shutdown
RG
V
IN
–
V
IN
+
REF
ADS7818
or
ADS7822
12-Bits
+5V
INA322
5
3
2
VOUT
8
7
6
41
V+ Shutdown
RG
VIN–
V–
VIN+
REF
fS < 100kHz
OPA336 Adjustable
Voltage
INA322
5
3
2
VOUT
8
7
6
41
V+ Shutdown
RG
VIN–
V–
VIN+
REF(1)
NOTE: (1) REF should be adjusted for the desired output level.
The value of REF affects the common-mode input range.
R
LIM
R
LIM
I
OVERLOAD
10mA max INA322
5
3
2
V
OUT
8
7
6
41
V+ Shutdown
RG
V
IN
–
V–
V
IN
+
REF
INA322
12
SBOS174B
OFFSET VOLTAGE ERROR CALCULATION
The offset voltage (VOS) of the INA322EA has a specified
maximum of 10mV with a +5V power supply and the
common-mode voltage at VS/2. Additional specifications
for power-supply rejection and common-mode rejection are
provided to allow the user to easily calculate worst-case
expected offset under the conditions of a given application.
Power Supply Rejection Ratio (PSRR) is specified in µV/V.
For the INA322, worst case PSRR is 250µV/V, which
means for each volt of change in power supply, the offset
may shift up to 250µV. Common-Mode Rejection Ratio
(CMRR) is specified in dB, which can be converted to
µV/V using the following equation:
CMRR (in µV/V) = 10[(CMRR in dB)/–20] • 106
For the INA322, the worst case CMRR over the specified
common-mode range is 60dB (at G = 25) or about
1mV/V This means that for every volt of change in com-
mon-mode, the offset will shift less than 1mV.
These numbers can be used to calculate excursions from the
specified offset voltage under different application condi-
tions. For example, an application might configure the
amplifier with a 3.3V supply with 1V common-mode. This
configuration varies from the specified configuration, repre-
senting a 1.7V variation in power supply (5V in the offset
specification versus 3.3V in the application) and a 0.65V
variation in common-mode voltage from the specified
VS/2.
Calculation of the worst-case expected offset would be as
follows:
Adjusted VOS = Maximum specified VOS +
(power-supply variation) • PSRR +
(common-mode variation) • CMRR
VOS = 10mV + (1.7V • 0.250mV/V) + (0.65V • 1mV/V)
= ±11.075mV
However, the typical value will be closer to 2.2mV (calcu-
lated using the typical values).
FEEDBACK CAPACITOR IMPROVES RESPONSE
For optimum settling time and stability with high-imped-
ance feedback networks, it may be necessary to add a
feedback capacitor across the feedback resistor, RF, as shown
in Figure 8. This capacitor compensates for the zero created
by the feedback network impedance and the INA322’s RG-
pin input capacitance (and any parasitic layout capacitance).
The effect becomes more significant with higher impedance
networks. Also, RX and CL can be added to reduce high-
frequency noise.
FIGURE 8. Feedback Capacitor Improves Dynamic Perfor-
mance.
It is suggested that a variable capacitor be used for the
feedback capacitor since input capacitance may vary be-
tween instrumentation amplifiers, and layout capacitance is
difficult to determine. For the circuit shown in Figure 8, the
value of the variable feedback capacitor should be chosen by
the following equation:
RIN • CIN = RF • CF
Where CIN is equal to the INA322’s RG-pin input capaci-
tance (typically 3pF) plus the layout capacitance. The ca-
pacitor can be varied until optimum performance is ob-
tained.
INA322
V+
V
OUT
R
IN
R
IN
• C
IN
= R
F
•
C
F
R
F
R
X
C
L
C
IN
Where C
IN
is equal to the INA322’s input capacitance
(approximately 3pF) plus any parastic layout capacitance.
5
3
2
8
7
6
4
1
Shutdown
RG
V
IN
–
V–
V
IN
+
REF
C
F
INA322 13
SBOS174B
FIGURE 9. Simplified ECG Circuit for Medical Applications.
APPLICATION CIRCUITS
Medical ECG Applications
Figure 9 shows the INA322 configured to serve as a low-
cost ECG amplifier, suitable for moderate accuracy heart-
rate applications such as fitness equipment. The input sig-
nals are obtained from the left and right arms of the patient.
The common-mode voltage is set by two 2MΩ resistors.
This potential through a buffer, provides optional right leg
drive. Filtering can be modified to suit application needs by
changing the capacitor value of the output filter.
Low-Power, Single-Supply Data Acquisition
Systems
Refer to Figure 5 to see the INA322 configured to drive an
ADS7818. Functioning at frequencies of up to 500kHz, the
INA322 is ideal for low-power data acquisition.
OPA336
OPA336
OPA336
Right Arm
Left Arm 1MΩ
REF
1MΩ
1MΩ
10kΩ
10kΩ
2kΩ
2kΩ
1.6nF
0.1µF
100kΩ
100kΩ
+5V
VR
VR
VR = +2.5V
2MΩ2MΩ
Right
Leg
INA322
5
3
2
8
7
6
41
V+ Shutdown
RG
VIN–
V–
VIN
+
VOUT PUT
PACKAGE OPTION ADDENDUM
www.ti.com 16-Aug-2012
Addendum-Page 1
PACKAGING INFORMATION
Orderable Device Status (1) Package Type Package
Drawing Pins Package Qty Eco Plan (2) Lead/
Ball Finish MSL Peak Temp (3) Samples
(Requires Login)
INA2322EA/250 ACTIVE TSSOP PW 14 250 Green (RoHS
& no Sb/Br) CU NIPDAU Level-2-260C-1 YEAR
INA2322EA/250G4 ACTIVE TSSOP PW 14 250 Green (RoHS
& no Sb/Br) CU NIPDAU Level-2-260C-1 YEAR
INA322EA/250 ACTIVE VSSOP DGK 8 250 Green (RoHS
& no Sb/Br) CU NIPDAUAGLevel-2-260C-1 YEAR
INA322EA/250G4 ACTIVE VSSOP DGK 8 250 Green (RoHS
& no Sb/Br) CU NIPDAUAGLevel-2-260C-1 YEAR
INA322EA/2K5 ACTIVE VSSOP DGK 8 2500 Green (RoHS
& no Sb/Br) CU NIPDAUAGLevel-2-260C-1 YEAR
INA322EA/2K5G4 ACTIVE VSSOP DGK 8 2500 Green (RoHS
& no Sb/Br) CU NIPDAUAGLevel-2-260C-1 YEAR
(1) The marketing status values are defined as follows:
ACTIVE: Product device recommended for new designs.
LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.
NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design.
PREVIEW: Device has been announced but is not in production. Samples may or may not be available.
OBSOLETE: TI has discontinued the production of the device.
(2) Eco Plan - The planned eco-friendly classification: Pb-Free (RoHS), Pb-Free (RoHS Exempt), or Green (RoHS & no Sb/Br) - please check http://www.ti.com/productcontent for the latest availability
information and additional product content details.
TBD: The Pb-Free/Green conversion plan has not been defined.
Pb-Free (RoHS): TI's terms "Lead-Free" or "Pb-Free" mean semiconductor products that are compatible with the current RoHS requirements for all 6 substances, including the requirement that
lead not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, TI Pb-Free products are suitable for use in specified lead-free processes.
Pb-Free (RoHS Exempt): This component has a RoHS exemption for either 1) lead-based flip-chip solder bumps used between the die and package, or 2) lead-based die adhesive used between
the die and leadframe. The component is otherwise considered Pb-Free (RoHS compatible) as defined above.
Green (RoHS & no Sb/Br): TI defines "Green" to mean Pb-Free (RoHS compatible), and free of Bromine (Br) and Antimony (Sb) based flame retardants (Br or Sb do not exceed 0.1% by weight
in homogeneous material)
(3) MSL, Peak Temp. -- The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder temperature.
Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is provided. TI bases its knowledge and belief on information
provided by third parties, and makes no representation or warranty as to the accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken and
continues to take reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on incoming materials and chemicals.
TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limited information may not be available for release.
PACKAGE OPTION ADDENDUM
www.ti.com 16-Aug-2012
Addendum-Page 2
In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI to Customer on an annual basis.
TAPE AND REEL INFORMATION
*All dimensions are nominal
Device Package
Type Package
Drawing Pins SPQ Reel
Diameter
(mm)
Reel
Width
W1 (mm)
A0
(mm) B0
(mm) K0
(mm) P1
(mm) W
(mm) Pin1
Quadrant
INA2322EA/250 TSSOP PW 14 250 180.0 12.4 6.9 5.6 1.6 8.0 12.0 Q1
INA322EA/250 VSSOP DGK 8 250 180.0 12.4 5.3 3.4 1.4 8.0 12.0 Q1
INA322EA/2K5 VSSOP DGK 8 2500 330.0 12.4 5.3 3.4 1.4 8.0 12.0 Q1
PACKAGE MATERIALS INFORMATION
www.ti.com 16-Aug-2012
Pack Materials-Page 1
*All dimensions are nominal
Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm)
INA2322EA/250 TSSOP PW 14 250 210.0 185.0 35.0
INA322EA/250 VSSOP DGK 8 250 210.0 185.0 35.0
INA322EA/2K5 VSSOP DGK 8 2500 367.0 367.0 35.0
PACKAGE MATERIALS INFORMATION
www.ti.com 16-Aug-2012
Pack Materials-Page 2
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