INA2331AIPWR [TI]
Low-Power, Single-Supply, CMOS INSTRUMENTATION AMPLIFIERS; 低功耗，单电源， CMOS仪表放大器
| 型号： | INA2331AIPWR |
| 厂家： | 
TEXAS INSTRUMENTS |
| 描述： | Low-Power, Single-Supply, CMOS INSTRUMENTATION AMPLIFIERS |
| 文件： | 总17页 (文件大小：293K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
INA331
IN
A
3
I
®
3
1
N
A
2
3
3
1
INA2331
SBOS215B – DECEMBER 2001 – REVISED APRIL 2003
Low-Power, Single-Supply, CMOS
INSTRUMENTATION AMPLIFIERS
FEATURES
APPLICATIONS
ꢀ DESIGNED FOR LOW COST
ꢀ INDUSTRIAL SENSOR AMPLIFIERS:
Bridge, RTD, Thermocouple, Position
ꢀ HIGH GAIN ACCURACY: G = 5, 0.02%, 2ppm/°C
ꢀ GAIN SET WITH EXT. RESISTORS FOR > 5V/V
ꢀ LOW OFFSET VOLTAGE: ±250µV
ꢀ PHYSIOLOGICAL AMPLIFIERS:
ECG, EEG, EMG
ꢀ A/D CONVERTER SIGNAL CONDITIONING
ꢀ DIFFERENTIAL LINE RECEIVERS WITH GAIN
ꢀ FIELD UTILITY METERS
ꢀ HIGH CMRR: 94dB DC, 50dB at 45kHz
ꢀ LOW BIAS CURRENT: 0.5pA
ꢀ BANDWIDTH, SLEW RATE: 2.0MHz, 5V/µs
ꢀ RAIL-TO-RAIL OUTPUT SWING: (V+) – 0.02V
ꢀ WIDE TEMPERATURE RANGE: –55°C to +125°C
ꢀ LOW QUIESCENT CURRENT: 490µA max/chan
ꢀ SHUT DOWN: 0.01µA
ꢀ PCMCIA CARDS
ꢀ AUDIO AMPLIFIERS
ꢀ COMMUNICATION SYSTEMS
ꢀ TEST EQUIPMENT
ꢀ AUTOMOTIVE INSTRUMENTATION
ꢀ MSOP-8 SINGLE AND TSSOP-14 DUAL PACKAGES
The INA331 rejects line noise and its harmonics, because
common-mode error remains low even at higher frequencies.
DESCRIPTION
The INA331 and INA2331 are rail-to-rail output, low-power
CMOS instrumentation amplifiers that offer wide range, single-
supply operation as well as bipolar-supply operation. The
INA331 family provides low-cost, low-noise amplification of
differential signals with a low quiescent current of 415µA
(dropping to 0.01µA when shutdown). Returning to normal
operation within microseconds, this INA can be used for
battery or multi-channel applications.
High bandwidth and slew rate makes the INA331 ideal for
directly driving sampling Analog-to-Digital (A/D) converters
as well as general-purpose applications.
With high precision, low cost, and small packages, the
INA331 outperforms discrete designs.
Additionally, because they are specified for wide temperature
range of –55°C to +125°C and operating range of –65°C to
+150°C, they can be used in demanding industrial and
automotive environments.
Configured internally in a gain of 5V/V, the INA331 offers
flexibility in higher gains by choosing external resistors.
R1
R2
RG
G = 5 + (5R2/R1)
INA2331
INA331
40kΩ
10kΩ
VREF
40kΩ
Ch A
10kΩ
VOUT
A1
A3
A2
VIN–
Ch B
VIN+
V+
V–
Shutdown
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.
PRODUCTION DATA information is current as of publication date.
Copyright © 2001-2003, Texas Instruments Incorporated
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
ELECTROSTATIC
DISCHARGE SENSITIVITY
Output Short-Circuit(3) .............................................................. Continuous
Operating Temperature .................................................. –55°C to +125°C
Storage Temperature ...................................................... –65°C to +150°C
Junction Temperature ...................................................................... 150°C
Lead Temperature (soldering, 10s) ................................................. 300°C
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.
NOTES: (1) Stresses above these ratings may cause permanent damage.
Exposure to absolute maximum conditions for extended periods may degrade
devicereliability.(2)Inputterminalsarediode-clampedtothepower-supplyrails.
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.
PACKAGE/ORDERING INFORMATION
SPECIFIED
PACKAGE
DESIGNATOR(1)
TEMPERATURE
PACKAGE
MARKING
ORDERING
NUMBER
TRANSPORT
MEDIA, QUANTITY
PRODUCT
PACKAGE-LEAD
RANGE
Single
INA331IDGK
MSOP-8
DGK
–55°C to +125°C
C31
"
INA331IDGKT
INA331IDGKR
INA331AIDGKT
INA331AIDGKR
Tape and Reel, 250
Tape and Reel, 2500
Tape and Reel, 250
Tape and Reel, 2500
"
"
MSOP-8
"
"
DGK
"
"
INA331AIDGK
–55°C to +125°C
C31
"
"
"
Dual
INA2331AIPW
TSSOP-14
PW
–55°C to +125°C
2331A
INA2331AIPWT
INA2331AIPWR
Tape and Reel, 250
Tape and Reel, 2500
"
"
"
"
"
NOTE: (1) For the most current specifications and package information, refer to our web site at www.ti.com.
PIN CONFIGURATION
Top View
INA2331
RGA
1
2
3
4
5
6
7
14 Shutdown A
13 OUTA
INA331
V
IN–A
IN+A
V–
V
RG
1
2
3
4
8
7
6
5
Shutdown
V+
V
12 REFA
11 V+
VIN–
VIN+
VOUT
V
IN+B
IN–B
10 REFB
V–
REF
V
9
8
V
OUTB
RGB
Shutdown B
MSOP-8 (DGK)
Dual, TSSOP-14 (PW)
INA331, INA2331
2
SBOS215B
www.ti.com
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 = 10kΩ, G = 25, and VREF = VS /2, unless otherwise noted.
INA331AIDGK
INA331IDGK
TYP
INA2331AIPW
PARAMETER
CONDITION
MIN
MAX
MIN
TYP
MAX
UNITS
INPUT
Input Offset Voltage, RTI
Over Temperature
Temperature Coefficient
vs Power Supply
vs Temperature
Long-Term Stability
Input Impedance
VS = +5V
±250
±500
±1.7
ꢀ
±1000
±2.1
µV
mV
VOS
dVOS/dT
PSRR
±5
±50
ꢀ
ꢀ
µV/°C
µV/V
µV/V
µV/month
Ω || pF
V
VS = +2.7V to +5.5V
±200
±220
ꢀ
ꢀ
±0.4
1013 || 3
ꢀ
ꢀ
Input Common-Mode Range
VS = 2.7V
VS = 5V
VS = 5V, VCM = 0.55V to 3.8V
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
90
77
72
1.5
3.8
ꢀ
ꢀ
80
75
70
ꢀ
ꢀ
V
dB
dB
dB
Common-Mode Rejection
–40°C to +85°C
Over Temperature
CMRR
94
94
ꢀ
ꢀ
dB
Crosstalk, Dual
114
dB
INPUT BIAS CURRENT
Bias Current
Offset Current
VCM = VS /2
IB
IOS
±0.5
±0.5
±10
±10
ꢀ
ꢀ
ꢀ
ꢀ
pA
pA
NOISE, RTI
RS = 0Ω
Voltage Noise: f = 10Hz
f = 100Hz
f = 1kHz
f = 0.1Hz to 10Hz
Current Noise: f = 1kHz
eN
280
96
46
7
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
nV/√Hz
nV/√Hz
nV/√Hz
µVp-p
iN
0.5
fA/√Hz
GAIN(1)
Gain Equation, Externally Set
Range of Gain
Gain Error
vs Temperature
Nonlinearity
G > 5
G = 5 + (5R2/R1)
ꢀ
5
1000
±0.1
±10
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
V/V
%
ppm/°C
% of FS
% of FS
G = 5
G = 5
±0.02
±2
ꢀ
ꢀ
ꢀ
ꢀ
G = 25(2), VS = 5V, VO = 0.05 to 4.95
±0.001
±0.010
Over Temperature
±0.002
±0.015
OUTPUT
Output Voltage Swing from Rail(3)
Over Temperature
Capacitance Load Drive
Short-Circuit Current
RL = 10kΩ
G > 10
50
50
25
ꢀ
ꢀ
ꢀ
mV
mV
pF
See Typical Characteristics
ꢀ
ꢀ
+48/–32
mA
FREQUENCY RESPONSE
Bandwidth, –3dB
Slew Rate
Settling Time, 0.1%
0.01%
BW
SR
G = 25
VS = 5V, G = 25
2.0
5
1.7
2.5
2
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
MHz
V/µs
µs
µs
µs
tS G = 25, CL = 100pF, VO = 2V step
Overload Recovery
50% Input Overload G = 25
POWER SUPPLY
Specified Voltage Range
Operating Voltage Range
Quiescent Current per Channel
Over Temperature
+2.7
+5.5
ꢀ
ꢀ
V
V
µA
µA
µA
+2.5 to +5.5
415
ꢀ
ꢀ
IQ
VSD > 2.5(3)
VSD < 0.8(3)
490
600
1
ꢀ
ꢀ
ꢀ
Shutdown Quiescent Current/Chan ISD
0.01
ꢀ
TEMPERATURE RANGE
Specified Range
Operating/Storage Range
–55
–65
+125
+150
ꢀ
ꢀ
ꢀ
ꢀ
°C
°C
Thermal Resistance
θJA MSOP-8, TSSOP-14 Surface Mount
150
ꢀ
°C/W
ꢀ Specifications same as INA331IDGK
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 to rail only if G ≥ 10. Output does not swing to positive rail if gain is less than 10. (3) See typical characteristic “Percent Overshoot vs Load Capacitance.”
(4) See typical characteristic “Shutdown Voltage vs Supply Voltage.”
INA331, INA2331
3
SBOS215B
www.ti.com
TYPICAL CHARACTERISTICS
At TA = +25°C, VS = 5V, VCM = VS /2, RL = 10kΩ, and CL = 100pF, unless otherwise noted.
COMMON-MODE REJECTION RATIO
vs FREQUENCY
GAIN vs FREQUENCY
80
70
60
50
40
30
20
10
0
120
100
80
60
40
20
0
Gain = 500
Gain = 100
Gain = 25
Gain = 5
–10
–20
10
100
1k
10k
100k
1M
10M
10
100
1k
10k
100k
Frequency (Hz)
Frequency (Hz)
POWER-SUPPLY REJECTION RATIO
vs FREQUENCY
MAXIMUM OUTPUT VOLTAGE vs FREQUENCY
VS = 5.5V
6
5
4
3
2
1
0
100
90
80
70
60
50
40
30
20
10
0
VS = 5.0V
VS = 2.7V
1M
10M
1
10
100
1k
10k
100k
100
1k
10k 100k
Frequency (Hz)
Frequency (Hz)
0.1Hz TO 10Hz VOLTAGE NOISE
NOISE vs FREQUENCY
10k
1k
100
10
1
100
10
0.1
1s/div
1
10
100
1k
10k
100k
Frequency (Hz)
INA331, INA2331
4
SBOS215B
www.ti.com
TYPICAL CHARACTERISTICS (Cont.)
At TA = +25°C, VS = 5V, VCM = VS /2, RL = 10kΩ, and CL = 100pF, unless otherwise noted.
COMMON-MODE INPUT RANGE
vs REFERENCE VOLTAGE
OUTPUT SWING vs LOAD RESISTANCE
25
6
5
4
3
2
1
0
20
Outside of Normal Operation
15
To Positive Rail
REF
Increasing
10
To Negative Rail
5
0
0
1
2
3
4
5
0
10k
20k
30k
40k
50k
Input Common-Mode Voltage (V)
RLOAD (Ω)
QUIESCENT CURRENT AND SHUTDOWN CURRENT
vs TEMPERATURE
QUIESCENT CURRENT AND SHUTDOWN CURRENT
vs POWER SUPPLY
600
550
500
450
400
350
300
250
200
150
100
50
500
450
400
350
300
250
200
150
100
50
IQ
IQ
ISD
ISD
0
0
–75 –50 –25
0
25
50
75
100 125 150
2.5
3
3.5
4
4.5
5
5.5
Temperature (°C)
Supply Voltage (V)
SHORT-CIRCUIT CURRENT vs POWER SUPPLY
ISC+
SHORT-CIRCUIT CURRENT vs TEMPERATURE
ISC+
60
50
40
30
20
10
0
60
50
40
30
20
10
0
ISC–
ISC–
2.5
3
3.5
4
4.5
5
5.5
–75 –50 –25
0
25
50
75 100 125 150
Supply Voltage (V)
Temperature (°C)
INA331, INA2331
5
SBOS215B
www.ti.com
TYPICAL CHARACTERISTICS (Cont.)
At TA = +25°C, VS = 5V, VCM = VS /2, RL = 10kΩ, and CL = 100pF, unless otherwise noted.
SMALL-SIGNAL STEP RESPONSE (G = 5)
SMALL-SIGNAL STEP RESPONSE (G = 100)
4µs/div
4µs/div
SMALL-SIGNAL STEP RESPONSE
(G = 5, CL = 1000pF)
SMALL-SIGNAL STEP RESPONSE
(G = 100, CL = 1000pF)
4µs/div
10µs/div
SMALL-SIGNAL STEP RESPONSE
(G = 100, CL = 4700pF)
LARGE-SIGNAL STEP RESPONSE (G = 25)
10µs/div
10µs/div
INA331, INA2331
6
SBOS215B
www.ti.com
TYPICAL CHARACTERISTICS (Cont.)
At TA = +25°C, VS = 5V, VCM = VS /2, RL = 10kΩ, and CL = 100pF, unless otherwise noted.
SETTLING TIME vs GAIN
PERCENT OVERSHOOT vs LOAD CAPACITANCE
60
50
40
30
20
10
0
100
Output 100mVp-p
Differential Drive
Output 2Vp-p
Differential
Input Drive
90
80
70
60
50
40
30
20
10
0
G = 5
0.01%
G = 25
0.1%
1
10
100
1k
10
100
1k
10k
Gain (V/V)
Load Capacitance (pF)
SHUTDOWN VOLTAGE vs SUPPLY VOLTAGE
Operation in this Region
SHUTDOWN TRANSIENT BEHAVIOR
3
2.5
2
VSD
is not Recommended
Normal Operation Mode
1.5
1
Shutdown Mode
VOUT
0.5
0
Part Draws Below 1µA Quiescent Current
50µs/div
2.5
3
3.5
4
4.5
5
5.5
Supply Voltage (V)
OFFSET VOLTAGE DRIFT
OFFSET VOLTAGE PRODUCTION DISTRIBUTION
PRODUCTION DISTRIBUTION
25
20
18
16
14
12
10
8
20
15
10
5
6
4
2
0
0
Offset Voltage (µV/°C)
Offset Voltage (mV)
INA331, INA2331
7
SBOS215B
www.ti.com
TYPICAL CHARACTERISTICS (Cont.)
At TA = +25°C, VS = 5V, VCM = VS /2, RL = 10kΩ, and CL = 100pF, unless otherwise noted.
SLEW RATE vs TEMPERATURE
INPUT BIAS CURRENT vs TEMPERATURE
8
7
6
5
4
3
2
1
0
10000
1000
100
10
1
0.1
–75 –50 –25
0
25
50
75 100 125 150
–75 –50 –25
0
25
50
75 100 125 150
Temperature (°C)
Temperature (°C)
CHANNEL SEPARATION vs FREQUENCY
OUTPUT VOLTAGE SWING vs OUTPUT CURRENT
120
100
80
60
40
20
0
5
4
3
2
1
0
125°C
25°C
–55°C
1
10
100
1k
10k
100k
1M
10M
0
5
10 15 20 25 30 35 40 45 50 55 60
Output Current (mA)
Frequency (Hz)
INA331, INA2331
8
SBOS215B
www.ti.com
OPERATING VOLTAGE
APPLICATIONS INFORMATION
The INA331 is a modified version of the classic “two op amp”
The INA331 family is fully specified over a supply range of
+2.7V to +5.5V, with key parameters tested over the tempera-
ture range of –55°C to +125°C. Parameters that vary signifi-
cantly with operating conditions, such as load conditions or
temperature, are shown in the Typical Characteristics.
instrumentation amplifier, with an additional gain amplifier.
Figure 1 shows the basic connections for the operation of the
INA331 and INA2331. The power supply should be capaci-
tively decoupled with 0.1µF capacitors as close to the INA331
as possible for noisy or high-impedance applications.
The INA331 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.
The output is referred to the reference terminal, which must
be at least 1.2V below the positive supply rail.
G = 5 + 5 (R2 / R1 )
DESIRED GAIN
Short VOUT to RG
(V/V)
R1
R2
R1
R2
for G = 5
5
OPEN SHORT
10
100kΩ 100kΩ
RG
1
50
10kΩ
90kΩ
100
10kΩ 190kΩ
40kΩ
10kΩ
5
REF
40kΩ
10kΩ
A1
6
VO = ((VIN+) – (VIN –)) • G
A3
2
3
VIN
VIN
–
A2
+
Also drawn in simplified form:
8
7
4
V+
Shutdown
7
3
5
2
VIN
REF
VIN
+
(For Single
Supply)
Shutdown
0.1µF
0.1µF
8
1
6
VOUT
INA331
V+
V–
–
4
V–
RG
FIGURE 1. Basic Connections.
+5V
V+
Shutdown
VIN
+
7
Bridge
Sensor
3
5
8
1
6
REF(1)
VIN
VOUT
INA331
–
2
4
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 Characteristics.
V–
RG
FIGURE 2. Single-Supply Bridge Amplifier.
INA331, INA2331
9
SBOS215B
www.ti.com
SETTING THE GAIN
how bias current path can be provided in the cases of
microphone applications, thermistor applications, ground re-
turns, and dc-coupled resistive bridge applications.
The ratio of R2 to R1, or the impedance between pins 1, 5,
and 6, determines the gain of the INA331. With an internally
set gain of 5, the INA331 can be programmed for gains
greater than 5 according to the following equation:
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.
G = 5 + 5 (R2/R1)
The INA331 is designed to provide accurate gain, with gain
error less than 0.1%. 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.
V+
Shutdown
VIN
+
7
3
5
2
COMMON-MODE INPUT RANGE
8
1
Microphone,
Hydrophone,
etc.
6
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 refer-
ence voltage according to the following equation:
VOUT
INA331
REF
VIN
–
4
47kΩ
VB
V–
RG
(1)
VOA1 = 5/4 VCM – 1/4 VREF
V+
Shutdown
VIN
+
(See typical characteristics “Common-Mode Input Range vs
Reference Voltage”).
7
3
5
2
8
6
VOUT
Transformer
INA331
REF
VIN
1
–
REFERENCE
4
Center-tap
provides bias
current return
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:
(1)
VB
V– RG
VEX
VOA2 = VREF + 5 (VIN+ – VIN–)
Bridge
Amplifier
V+
Shutdown
For ensured operation, VOA2 should be less than
VIN
+
7
INA331
4
3
5
2
Bridge
Sensor
VDD – 1.2V.
8
1
The reference pin requires a low-impedance connection. As
little as 160Ω in series with the reference pin will degrade the
CMRR to 80dB. The reference pin may be used to compen-
sate 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).
6
VOUT
REF
VIN
–
Bridge resistance
provides bias
current return
V– RG
NOTE: (1) VB is bias voltage within
common-mode range, dependent
on REF.
INPUT BIAS CURRENT RETURN
With a high input impedance of 1013Ω, the INA331 is ideal for
use with high-impedance sources. The input bias current of
less than 10pA makes the INA331 nearly independent of
input impedance and ideal for low-power applications.
FIGURE 3. Providing an Input Common-Mode Path.
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-mode
range and the input amplifier will saturate. Figure 3 shows
INA331, INA2331
10
SBOS215B
www.ti.com
SHUTDOWN MODE
+5V
The shutdown pin of the INA331 is nominally connected to V+.
When the pin is pulled below 0.8V on a 5V supply, the INA331
goes into sleep mode within nanoseconds. For actual shut-
down threshold, see typical characteristic “Shutdown Voltage
vs Supply Voltage”. Drawing less than 2µA 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
INA331 suitable for multiplexing.
0.1µF
V+
7
0.1µF
Shutdown
3
5
2
VIN
REF
VIN
+
8
VOUT
6
INA331
1
VOUT
OPA340
–
4
V–
RG
RAIL-TO-RAIL OUTPUT
FIGURE 5. Output Buffering Circuit. Able to drive loads as
A class AB output stage with common-source transistors is
used to achieve rail-to-rail output for gains of 10 or greater.
For resistive loads greater than 10kΩ, the output voltage can
swing to within 25 millivolts of the supply rail while maintain-
ing low gain error. For heavier loads and over temperature,
see the typical characteristic “Output Voltage Swing vs
Output Current.” The INA331’s low output impedance at high
frequencies makes it suitable for directly driving Capacitive-
Input A/D converters, as shown in Figure 4.
low as 600Ω.
V+
Shutdown
7
3
VIN+
8
1
REF(1)
6
5
2
VOUT
INA331
VIN–
4
V–
RG
+5V
V+
Shutdown
OPA336
7
3
5
2
VIN+
REF
Adjustable
Voltage
12-Bits
8
1
VOUT
ADS7818
or
ADS7822
6
INA331
NOTE: (1) REF should be adjusted for the desired output level.
The value of REF affects the common-mode input range.
VIN–
4
V–
RG
FIGURE 6. Optional Offset Trimming Voltage.
fS < 100kHz
INPUT PROTECTION
FIGURE 4. INA331 Directly Drives Capacitive-Input, High-
Speed A/D Converter.
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.
OUTPUT BUFFERING
The INA331 is optimized for a load impedance of 10kΩ or
greater. For higher output current the INA331 can be buff-
ered using the OPA340, as shown in Figure 5. The OPA340
can swing within 50mV of the supply rail, driving a 600Ω load.
The OPA340 is available in the tiny MSOP-8 package.
V+
OFFSET TRIMMING
Shutdown
RLIM
7
3
5
2
The INA331 is laser trimmed for low offset voltage. 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.
VIN
+
8
1
IOVERLOAD
10mA max
6
VOUT
REF
INA331
VIN
–
4
RLIM
V–
RG
FIGURE 7. Sample Output Buffering Circuit.
INA331, INA2331
11
SBOS215B
www.ti.com
OFFSET VOLTAGE ERROR CALCULATION
FEEDBACK CAPACITOR IMPROVES RESPONSE
The offset voltage (VOS) of the INA331IDGK is specified at a
maximum of 500µV with a +5V power supply and the com-
mon-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.
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 INA331’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.
Power-Supply Rejection Ratio (PSRR) is specified in µV/V.
For the INA331, worst case PSRR is 200µV/V, which means
for each volt of change in power supply, the offset may shift
up to 200µV. Common-Mode Rejection Ratio (CMRR) is
specified in dB, which can be converted to µV/V using the
following equation:
V+
Shutdown
7
3
VIN+
CMRR (in µV/V) = 10[(CMRR in dB)/–20] • 106
8
INA331
RX
6
5
2
VOUT
REF
CIN
For the INA331, the worst case CMRR over the specified
common-mode range is 90dB (at G = 25) or about 30µV/V
This means that for every volt of change in common-mode,
the offset will shift less than 30µV.
CL
1
VIN–
RG
4
V–
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 ampli-
fier with a 3.3V supply with 1V common-mode. This configu-
ration 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.
RIN
RF
RIN • CIN = RF • CF
CF
Where CIN is equal to the INA331’s input capacitance
(approximately 3pF) plus any parastic layout capacitance.
FIGURE 8. Feedback Capacitor Improves Dynamic Perfor-
mance.
Calculation of the worst-case expected offset would be as
follows:
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:
Adjusted VOS = Maximum specified VOS
+
(power-supply variation) • PSRR +
(common-mode variation) • CMRR
VOS = 0.5mV + (1.7V • 200µV) + (0.65V • 30µV)
= ±0.860mV
RIN • CIN = RF • CF
However, the typical value will be smaller, as seen in the
Typical Characteristics.
Where CIN is equal to the INA331’s RG-pin input capacitance
(typically 3pF) plus the layout capacitance. The capacitor can
be varied until optimum performance is obtained.
INA331, INA2331
12
SBOS215B
www.ti.com
Filtering can be modified to suit application needs by chang-
ing the capacitor value of the output filter.
APPLICATION CIRCUITS
MEDICAL ECG APPLICATIONS
Figure 9 shows the INA331 configured to serve as a low-cost
ECG amplifier, suitable for moderate accuracy heart-rate
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 drive.
LOW-POWER, SINGLE-SUPPLY DATA
ACQUISITION SYSTEMS
Refer to Figure 4 to see the INA331 configured to drive an
ADS7818. Functioning at frequencies of up to 500kHz, the
INA331 is ideal for low-power data acquisition.
VR
OPA336
1.6nF
0.1µF
V+
1MΩ
Shutdown
1MΩ
100kΩ
100kΩ
VIN
REF
VIN
+
7
3
Left Arm
8
1
10kΩ
10kΩ
6
5
2
INA331
VOUT PUT
–
OPA336
Right Arm
4
VR
+5V
V–
RG
1MΩ
2MΩ
2MΩ
2kΩ
VR = +2.5V
Right
Leg
OPA336
2kΩ
FIGURE 9. Simplified ECG Circuit for Medical Applications.
INA331, INA2331
13
SBOS215B
www.ti.com
PACKAGE DRAWINGS
DGK (R-PDSO-G8)
PLASTIC SMALL-OUTLINE PACKAGE
0,38
0,25
M
0,65
8
0,08
5
0,15 NOM
3,05
2,95
4,98
4,78
Gage Plane
0,25
0°–6°
1
4
0,69
3,05
2,95
0,41
Seating Plane
0,10
0,15
0,05
1,07 MAX
4073329/C 08/01
NOTES: A. All linear dimensions are in millimeters.
B. This drawing is subject to change without notice.
C. Body dimensions do not include mold flash or protrusion.
D. Falls within JEDEC MO-187
INA331, INA2331
14
SBOS215B
www.ti.com
PACKAGE DRAWINGS (Cont.)
PW (R-PDSO-G**)
PLASTIC SMALL-OUTLINE PACKAGE
14 PINS SHOWN
0,30
0,19
M
0,10
0,65
14
8
0,15 NOM
4,50
4,30
6,60
6,20
Gage Plane
0,25
1
7
0°–8°
A
0,75
0,50
Seating Plane
0,10
0,15
0,05
1,20 MAX
PINS **
8
14
16
20
24
28
DIM
3,10
2,90
5,10
4,90
5,10
4,90
6,60
6,40
7,90
9,80
9,60
A MAX
A MIN
7,70
4040064/F 01/97
NOTES: A. All linear dimensions are in millimeters.
B. This drawing is subject to change without notice.
C. Body dimensions do not include mold flash or protrusion not to exceed 0,15.
D. Falls within JEDEC MO-153
INA331, INA2331
15
SBOS215B
www.ti.com
PACKAGE OPTION ADDENDUM
www.ti.com
3-Oct-2003
PACKAGING INFORMATION
ORDERABLE DEVICE
STATUS(1)
PACKAGE TYPE
PACKAGE DRAWING
PINS
PACKAGE QTY
INA2331AIPWR
INA2331AIPWT
INA331AIDGKR
INA331AIDGKT
INA331IDGKR
INA331IDGKT
ACTIVE
ACTIVE
ACTIVE
ACTIVE
ACTIVE
ACTIVE
TSSOP
TSSOP
VSSOP
VSSOP
VSSOP
VSSOP
PW
PW
14
14
8
2500
250
DGK
DGK
DGK
DGK
2500
250
8
8
2500
250
8
(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.
IMPORTANT NOTICE
Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, modifications,
enhancements, improvements, and other changes to its products and services at any time and to discontinue
any product or service without notice. Customers should obtain the latest relevant information before placing
orders and should verify that such information is current and complete. All products are sold subject to TI’s terms
and conditions of sale supplied at the time of order acknowledgment.
TI warrants performance of its hardware products to the specifications applicable at the time of sale in
accordance with TI’s standard warranty. Testing and other quality control techniques are used to the extent TI
deems necessary to support this warranty. Except where mandated by government requirements, testing of all
parameters of each product is not necessarily performed.
TI assumes no liability for applications assistance or customer product design. Customers are responsible for
their products and applications using TI components. To minimize the risks associated with customer products
and applications, customers should provide adequate design and operating safeguards.
TI does not warrant or represent that any license, either express or implied, is granted under any TI patent right,
copyright, maskworkright, orotherTIintellectualpropertyrightrelatingtoanycombination, machine, orprocess
in which TI products or services are used. Information published by TI regarding third-party products or services
does not constitute a license from TI to use such products or services or a warranty or endorsement thereof.
Use of such information may require a license from a third party under the patents or other intellectual property
of the third party, or a license from TI under the patents or other intellectual property of TI.
Reproduction of information in TI data books or data sheets is permissible only if reproduction is without
alteration and is accompanied by all associated warranties, conditions, limitations, and notices. Reproduction
of this information with alteration is an unfair and deceptive business practice. TI is not responsible or liable for
such altered documentation.
Resale of TI products or services with statements different from or beyond the parameters stated by TI for that
product or service voids all express and any implied warranties for the associated TI product or service and
is an unfair and deceptive business practice. TI is not responsible or liable for any such statements.
Following are URLs where you can obtain information on other Texas Instruments products and application
solutions:
Products
Applications
Audio
Amplifiers
amplifier.ti.com
www.ti.com/audio
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dataconverter.ti.com
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www.ti.com/automotive
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dsp.ti.com
Broadband
Digital Control
Military
www.ti.com/broadband
www.ti.com/digitalcontrol
www.ti.com/military
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Logic
interface.ti.com
logic.ti.com
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Microcontrollers
power.ti.com
Optical Networking
Security
www.ti.com/opticalnetwork
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microcontroller.ti.com
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Wireless
www.ti.com/wireless
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Post Office Box 655303 Dallas, Texas 75265
Copyright 2003, Texas Instruments Incorporated
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