TI INA322 Micropower, single-supply, cmos ntation amplifier Datasheet

INA
322
INA322
INA2322
®
SBOS174B – DECEMBER 2000 – REVISED FEBRUARY 2006
microPower, Single-Supply, CMOS
INSTRUMENTATION AMPLIFIER
FEATURES
APPLICATIONS
● 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
● 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
DESCRIPTION
Configured internally for 5V/V gain, the INA322 offers exceptional flexibility with user-programmable external gain resistors. The INA322 reduces common-mode error over frequency and with CMRR remaining high up to 3kHz, line noise
and line harmonics are rejected.
The INA322 family is a series of low cost, rail-to-rail output,
micropower CMOS instrumentation amplifiers that offer widerange, 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.
The low-power design does not compromise on bandwidth or
slew rate, making the INA322 ideal for driving sampling Analog-to-Digital (A/D) converters as well as general-purpose
applications. With high precision, low cost, and small packaging, the INA322 outperforms discrete designs, while offering
reliability and performance.
R1
160kΩ
40kΩ
RG
40kΩ
R2
160kΩ
REF
A1
A3
VIN–
VOUT
A2
VIN+
Gain = 5 + 5(R2/R1)
VOUT = (VIN+ – VIN–) • Gain
Shutdown
V+
V–
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.
Copyright © 2000-2006, Texas Instruments Incorporated
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.
www.ti.com
ABSOLUTE MAXIMUM RATINGS(1)
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.
ELECTROSTATIC
DISCHARGE SENSITIVITY
This integrated circuit can be damaged by ESD. Texas Instruments 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/ORDERING INFORMATION(1)
PRODUCT
PACKAGE-LEAD
PACKAGE
DESIGNATOR
PACKAGE
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.
PIN CONFIGURATIONS
Top View
INA2322
INA322
RGA
1
14
Shutdown A
RG
1
8
Shutdown
VIN–A
2
13
VOUTA
VIN–
2
7
V+
VIN+A
3
12
REFA
VIN+
3
6
VOUT
V–
4
11
V+
V–
4
5
REF
VIN+B
5
10
REFB
VIN–B
6
9
VOUTB
RGB
7
8
Shutdown B
MSOP-8 (EA)
Dual, TSSOP-14 (EA)
2
INA322
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
INPUT
Input Offset Voltage, RTI
Over Temperature
vs Temperature
vs Power Supply
Over Temperature
Long-Term Stability
Input Impedance
Input Common-Mode Range
Common-Mode Rejection
Over Temperature
CONDITION
VOS
dVOS/dT
PSRR
MIN
VS = +5V
±2
VS = +2.7V to +5.5V
±7
±50
±0.4
1013 || 3
CMRR
VS = 2.7V
VS = 5V
VS = 5V, VCM = 0.55V to 3.8V
VS = 5V, VCM = 0.55V to 3.8V
VS = 2.7V, VCM = 0.35V to 1.5V
0.35
0.55
60
60
INPUT BIAS CURRENT
Bias Current
Offset Current
NOISE, RTI
Voltage Noise: f = 10Hz
f = 100Hz
f = 1kHz
f = 0.1Hz to 10Hz
Current Noise: f = 1kHz
Slew Rate
Settling Time, 0.1%
0.01%
Overload Recovery
POWER SUPPLY
Specified Voltage Range
Operating Voltage Range
Quiescent Current per Channel
Over Temperature
Shutdown Quiescent Current/Chan
mV
mV
µV/°C
µV/V
µV/V
µV/month
Ω || pF
V
V
dB
dB
dB
dB
±250
±260
73
±10
±10
pA
pA
R S = 0Ω
G>5
±0.07
±2
±0.001
±0.002
G=5
G = 25, VS = 5V, VO = 0.05 to 4.95
G ≥ 10
nV/√Hz
nV/√Hz
nV/√Hz
µVp-p
fA/√Hz
G = 5 + 5(R2/R1)
5
OUTPUT
Output Voltage Swing from Rail(2, 5)
FREQUENCY RESPONSE
Bandwidth, –3dB
±10
±11
500
190
100
20
3
GAIN(1)
Gain Equation, Externally Set
Range of Gain
Gain Error
vs Temperature
Nonlinearity
Over Temperature
Over Temperature
Capacitance Load Drive
Short-Circuit Current
UNITS
1.5
3.8
±0.5
±0.5
IB
IOS
en
MAX
73
110
Crosstalk, Dual
TEMPERATURE RANGE
Specified Range
Operating/Storage Range
Thermal Resistance
TYP
50
1000
±0.4
±10
±0.010
±0.015
25
mV
50
mV
pF
See Typical Characteristic(3)
8
16
ISC–
ISC+
V/V
%
ppm/°C
% of FS
% of FS
mA
BW
G=5
500
kHz
SR
tS
VS = 5V, G = 25
G = 5, CL = 50pF, VO = 2V step
0.4
8
12
2
V/µs
µs
µs
µs
50% Input Overload G = 25
+2.7
+5.5
IQ
VSD > 2.5(4)
+2.5 to +5.5
40
ISD
VSD < 0.8(4)
0.01
–55
–65
θJA
MSOP-8, TSSOP-14 Surface Mount
60
70
1
+125
+150
150
V
V
µA
µA
µA
°C
°C
°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
SBOS174B
3
TYPICAL CHARACTERISTICS
At TA = +25°C, VS = 5V, VCM = 1/2VS, RL = 25kΩ, CL = 50pF, unless otherwise noted.
COMMON-MODE REJECTION RATIO
vs FREQUENCY
GAIN vs FREQUENCY
120
80
70
60
50
80
Gain = 100
CMRR (dB)
Gain (dB)
100
Gain = 500
40
Gain = 25
30
20
Gain = 5
10
0
60
40
20
–10
–20
0
10
100
1k
10k
100k
1M
10
10M
100
POWER-SUPPLY REJECTION RATIO
vs FREQUENCY
Maximum Output Voltage (Vp-p)
90
80
70
PSRR (dB)
100k
10k
MAXIMUM OUTPUT VOLTAGE vs FREQUENCY
6
100
60
50
40
30
20
10
0
VS = 5.5V
5
VS = 5.0V
4
VS = 2.7V
3
2
1
0
1
10
100
1k
10k
100
100k
NOISE vs FREQUENCY
10
100
1
10
100
1k
100k
1M
10M
10k
0.1
100k
10µv/div
1k
INoise (fA/√Hz)
100
10
10k
0.1Hz TO 10Hz VOLTAGE NOISE
10k
1
1k
Frequency (Hz)
Frequency (Hz)
VNoise (nV/√Hz)
1k
Frequency (Hz)
Frequency (Hz)
1s/div
Frequency (Hz)
4
INA322
SBOS174B
TYPICAL CHARACTERISTICS (Cont.)
At TA = +25°C, VS = 5V, VCM = 1/2VS, RL = 25kΩ, CL = 50pF, unless otherwise noted.
COMMON-MODE INPUT RANGE
vs REFERENCE VOLTAGE
OUTPUT SWING vs LOAD RESISTANCE
6
Output—Referred to Ground (V)
25
15
To Positive Rail
10
To Negative Rail
5
Outside of Normal Operation
4
3
REF
Increasing
2
1
0
0
0
20k
40k
80k
60k
0
100k
2
4
3
5
RLoad (Ω)
QUIESCENT CURRENT AND SHUTDOWN CURRENT
vs POWER SUPPLY
QUIESCENT CURRENT AND SHUTDOWN CURRENT
vs TEMPERATURE
50
500
60
45
450
55
350
300
25
250
20
200
15
150
10
40
IQ (µA)
30
0
3
3.5
4
4.5
5
400
IQ
35
30
300
25
20
200
15
100
ISD
5
500
45
ISD (nA)
35
600
50
400
IQ
2.5
1
Input Common-Mode Voltage (V)
40
IQ (µA)
5
10
50
5
0
0
5.5
ISD
–75
–50
–25
0
Supply Voltage (V)
25
50
75
100
125
100
0
150
Temperature (°C)
SHORT-CIRCUIT CURRENT vs TEMPERATURE
SHORT-CIRCUIT CURRENT vs POWER SUPPLY
20
30
25
ISC+
15
10
ISC (mA)
ISC (mA)
20
ISC–
ISC+
15
10
5
ISC–
5
0
0
2.5
3
3.5
4
4.5
Supply Voltage (V)
INA322
SBOS174B
5
5.5
–75
–50
–25
0
25
50
75
100
125
150
Temperature (°C)
5
ISD (nA)
Swing to Rail (mV)
20
TYPICAL CHARACTERISTICS (Cont.)
At TA = +25°C, VS = 5V, VCM = 1/2VS, RL = 25kΩ, CL = 50pF, unless otherwise noted.
50µs/div
SMALL-SIGNAL STEP RESPONSE
(G = 5, CL = 1000pF)
SMALL-SIGNAL STEP RESPONSE
(G = 100, CL = 1000pF)
50mv/div
100mv/div
10µs/div
50µs/div
SMALL-SIGNAL STEP RESPONSE
(G = 100, CL = 5000pF)
LARGE-SIGNAL STEP RESPONSE
(G = 25, CL = 50pF)
1V/div
50mv/div
10µs/div
50µs/div
6
SMALL-SIGNAL STEP RESPONSE (G = 100)
50mv/div
100mv/div
SMALL-SIGNAL STEP RESPONSE (G = 5)
50µs/div
INA322
SBOS174B
TYPICAL CHARACTERISTICS (Cont.)
At TA = +25°C, VS = 5V, VCM = 1/2VS, RL = 25kΩ, CL = 50pF, unless otherwise noted.
SETTLING TIME vs GAIN
PERCENT OVERSHOOT vs LOAD CAPACITANCE
100
60
Output 2Vp-p
Differential
Input Drive
Settling Time (µs)
80
Output 100mVp-p
Differential
Input Drive
50
70
Overshoot (%)
90
0.01%
60
50
40
30
G=5
40
30
G = 25
20
0.1%
20
10
10
0
0
1
10
100
1000
10
100
1k
Gain (V/V)
Load Capacitance (pF)
SHUTDOWN VOLTAGE vs SUPPLY VOLTAGE
SHUTDOWN TRANSIENT BEHAVIOR
10k
3
Operation in this Region
is not Recommended
2.5
VSD
2
1V/div
Shutdown (V)
Normal Operation Mode
1.5
1
VOUT
Shutdown Mode
0.5
Part Draws Below 1µA Quiescent Current
0
2.3
3
3.5
4
4.5
5
50µs/div
5.5
Supply Voltage (V)
OFFSET VOLTAGE DRIFT
PRODUCTION DISTRIBUTION
20
18
18
Percentage of Amplifiers (%)
20
16
14
12
10
8
6
4
16
14
12
10
8
6
4
2
0
0
–20
–18
–16
–14
–12
–10
–8
–6
–4
–2
0
2
4
6
8
10
12
14
16
18
20
2
–10
–9
–8
–7
–6
–5
–4
–3
–2
–1
0
1
2
3
4
5
6
7
8
9
10
Percentage of Amplifiers (%)
OFFSET VOLTAGE PRODUCTION DISTRIBUTION
Offset Voltage (mV)
Offset Voltage Drift (µV/°C)
INA322
SBOS174B
7
TYPICAL CHARACTERISTICS (Cont.)
At TA = +25°C, VS = 5V, VCM = 1/2VS, RL = 25kΩ, CL = 50pF, unless otherwise noted.
INPUT BIAS CURRENT vs TEMPERATURE
10k
0.8
1k
Input Bias Current (pA)
SR (V/µs)
SLEW RATE vs TEMPERATURE
1
0.6
0.4
0.2
0
100
10
0
0.1
–75
–50
–25
0
25
50
75
100
125
–75
150
–50
–25
0
CROSSTALK vs FREQUENCY
75
100
125
150
5
100
4
Output Voltage (V)
Crosstalk (dB)
50
OUTPUT VOLTAGE SWING vs OUTPUT CURRENT
120
80
60
40
125°C
25°C
–55°C
3
2
125°C
25°C
–55°C
1
20
0
0
0.1
1
10
100
1k
Frequency (Hz)
8
25
Temperature (°C)
Temperature (°C)
10k
100k
1M
0
2
4
6
8
10
12
14
16
18
20
22
24
Output Current (mA)
INA322
SBOS174B
APPLICATIONS INFORMATION
OPERATING VOLTAGE
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 capacitively decoupled with 0.1µF capacitors as close to the
INA322 as possible for noisy or high-impedance applications.
The output is referred to the reference terminal, which must
be at least 1.2V below the positive supply rail.
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 conditions 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.
G = 5 + 5(R2 / R1 )
Short VOUT to RG
for G = 5
R1
DESIRED GAIN
(V/V)
R2
5
10
50
100
RG
1
REF
VIN–
VIN+
5
160kΩ
40kΩ
R2
R1
OPEN SHORT
100kΩ 100kΩ
10kΩ
90kΩ
10kΩ 190kΩ
160kΩ
40kΩ
A1
2
A3
6
VO = ((VIN+) – (VIN –)) • G
A2
3
Also drawn in simplified form:
8
4
7
Shutdown
VIN+
(For Single
Supply)
0.1µF
V+
7
5
INA322
0.1µF
8
REF
V–
V+
Shutdown
3
VIN–
2
6
VOUT
1
4
V–
RG
FIGURE 1. Basic Connections.
+5V
Bridge
Sensor
VIN+
3
V+
7
REF(1)
5
INA322
Shutdown
8
VIN–
6
VOUT
1
2
4
V–
RG
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.
FIGURE 2. Bridge Amplifier of the INA322.
INA322
SBOS174B
9
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)
V+
VIN+ 3
8
Microphone,
Hydrophone,
etc.
REF
47kΩ
(See Typical Characteristic Curves for Input CommonMode 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 equation:
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-
10
INA322
6
VOUT
1
4
V–
RG
VB(1)
V+
INPUT COMMON-MODE RANGE
VOA1 = 5/4 VCM – 1/4 VREF
5
VIN– 2
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.
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 performance. 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:
Shutdown
7
VIN+ 3
Shutdown
7
8
Transformer
REF
5
INA322
6
VOUT
1
VIN– 2
4
VB(1)
Bridge
Amplifier
V–
Center-tap
RG provides bias
current return
VEX
V+
Bridge
Sensor
VIN+ 3
Shutdown
7
8
REF
5
INA322
6
VOUT
1
VIN– 2
4
V–
RG Bridge resistance
provides bias
current return
NOTE: (1) VB is bias voltage within
common-mode range, dependent
on REF.
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 balanced input. The advantages are lower input offset voltage
due to bias current flowing through the source impedance
and better high-frequency gain.
INA322
SBOS174B
OUTPUT BUFFERING
+5V
The INA322 is optimized for a load impedance of 10kΩ or
greater. For higher output current the INA322 can be buffered 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.
0.1µF
VIN+
3
V+
7
5
INA322
8
REF
VIN–
0.1µF
Shutdown
6
VOUT
1
2
OFFSET TRIMMING
VOUT
OPA340
4
RG
FIGURE 4. Output Buffering Circuit. Able to drive loads
as low as 600Ω.
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 commonmode rejection.
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 microseconds, the shutdown feature is useful for portable applications.
Once in ‘sleep-mode’ the amplifier has high output impedance, making the INA322 suitable for multiplexing.
V+
VIN+
+5V
V+
7
5
INA322
VIN–
2
1
4
V–
INA322
4
V–
6
VOUT
ADS7818
or
ADS7822
Adjustable
Voltage
FIGURE 6. Optional Offset Trimming Voltage.
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.
V+
12-Bits
RLIM
3
VIN+
IOVERLOAD
10mA max
RG
fS < 100kHz
FIGURE 5. INA322 Directly Drives a Capacitive-Input,
A/D Converter.
SBOS174B
RG
NOTE: (1) REF should be adjusted for the desired output level.
The value of REF affects the common-mode input range.
REF
5
Shutdown
7
8
INA322
6
VOUT
1
2
VIN–
INA322
VOUT
1
2
VIN–
6
Shutdown
8
REF
5
OPA336
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.
3
7
8
REF(1)
RAIL-TO-RAIL OUTPUT
VIN+
Shutdown
3
4
RLIM
V–
RG
FIGURE 7. Input Protection.
11
OFFSET VOLTAGE ERROR CALCULATION
FEEDBACK CAPACITOR IMPROVES RESPONSE
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:
For optimum settling time and stability with high-impedance 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 RGpin 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 highfrequency noise.
CMRR (in µV/V) = 10[(CMRR in dB)/–20] • 106
V+
VIN+
7
3
Shutdown
8
INA322
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 common-mode, the offset will shift less than 1mV.
These numbers can be used to calculate excursions from the
specified offset voltage under different application conditions. For example, an application might configure the
amplifier with a 3.3V supply with 1V common-mode. This
configuration varies from the specified configuration, representing 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 (calculated using the typical values).
12
REF
6
5
VOUT
CIN
CL
1
VIN–
RX
2
4
RG
V–
RIN
RF
RIN • CIN = RF • CF
CF
Where CIN is equal to the INA322’s input capacitance
(approximately 3pF) plus any parastic layout capacitance.
FIGURE 8. Feedback Capacitor Improves Dynamic Performance.
It is suggested that a variable capacitor be used for the
feedback capacitor since input capacitance may vary between 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 capacitance (typically 3pF) plus the layout capacitance. The capacitor can be varied until optimum performance is obtained.
INA322
SBOS174B
APPLICATION CIRCUITS
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.
Medical ECG Applications
Figure 9 shows the INA322 configured to serve as a lowcost ECG amplifier, suitable for moderate accuracy heartrate applications such as fitness equipment. The input signals 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
VR
OPA336
1.6nF
0.1µF
V+
100kΩ
VIN+ 3
Left Arm
100kΩ
Right Arm
Shutdown
7
8
REF
5
VIN–
2
INA322
1
V–
2MΩ
10kΩ
6
10kΩ
OPA336
VOUT PUT
VR
4
+5V
1MΩ
1MΩ
RG
1MΩ
2MΩ
2kΩ
VR = +2.5V
2kΩ
OPA336
Right
Leg
FIGURE 9. Simplified ECG Circuit for Medical Applications.
INA322
SBOS174B
13
PACKAGE OPTION ADDENDUM
www.ti.com
11-Jul-2013
PACKAGING INFORMATION
Orderable Device
Status
(1)
Package Type Package Pins Package
Drawing
Qty
Eco Plan
Lead/Ball Finish
(2)
MSL Peak Temp
Op Temp (°C)
Device Marking
(3)
(4/5)
INA2322EA/250
ACTIVE
TSSOP
PW
14
250
Green (RoHS
& no Sb/Br)
CU NIPDAU
Level-2-260C-1 YEAR
-40 to 85
INA
2322EA
INA2322EA/250G4
ACTIVE
TSSOP
PW
14
250
Green (RoHS
& no Sb/Br)
CU NIPDAU
Level-2-260C-1 YEAR
-40 to 85
INA
2322EA
INA322EA/250
ACTIVE
VSSOP
DGK
8
250
Green (RoHS CU NIPDAUAG Level-2-260C-1 YEAR
& no Sb/Br)
-55 to 125
C22
INA322EA/250G4
ACTIVE
VSSOP
DGK
8
250
Green (RoHS CU NIPDAUAG Level-2-260C-1 YEAR
& no Sb/Br)
-55 to 125
C22
INA322EA/2K5
ACTIVE
VSSOP
DGK
8
2500
Green (RoHS CU NIPDAUAG Level-2-260C-1 YEAR
& no Sb/Br)
-55 to 125
C22
INA322EA/2K5G4
ACTIVE
VSSOP
DGK
8
2500
Green (RoHS CU NIPDAUAG Level-2-260C-1 YEAR
& no Sb/Br)
-55 to 125
C22
(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.
(4)
There may be additional marking, which relates to the logo, the lot trace code information, or the environmental category on the device.
(5)
Multiple Device Markings will be inside parentheses. Only one Device Marking contained in parentheses and separated by a "~" will appear on a device. If a line is indented then it is a continuation
of the previous line and the two combined represent the entire Device Marking for that device.
Addendum-Page 1
Samples
PACKAGE OPTION ADDENDUM
www.ti.com
11-Jul-2013
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.
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.
Addendum-Page 2
PACKAGE MATERIALS INFORMATION
www.ti.com
16-Aug-2012
TAPE AND REEL INFORMATION
*All dimensions are nominal
Device
Package Package Pins
Type Drawing
INA2322EA/250
TSSOP
PW
14
INA322EA/250
VSSOP
DGK
INA322EA/2K5
VSSOP
DGK
SPQ
Reel
Reel
A0
Diameter Width (mm)
(mm) W1 (mm)
B0
(mm)
K0
(mm)
P1
(mm)
W
Pin1
(mm) Quadrant
250
180.0
12.4
6.9
5.6
1.6
8.0
12.0
Q1
8
250
180.0
12.4
5.3
3.4
1.4
8.0
12.0
Q1
8
2500
330.0
12.4
5.3
3.4
1.4
8.0
12.0
Q1
Pack Materials-Page 1
PACKAGE MATERIALS INFORMATION
www.ti.com
16-Aug-2012
*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
Pack Materials-Page 2
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