Burr-Brown INA332 Low-power, single-supply, cmos instrumentation amplifier Datasheet

INA3
32
INA
233
2
INA332
INA2332
®
SBOS216A – DECEMBER 2001
Low-Power, Single-Supply, CMOS
INSTRUMENTATION AMPLIFIERS
FEATURES
APPLICATIONS
●
●
●
●
●
●
DESIGNED FOR LOW COST
HIGH GAIN ACCURACY: G = 5, 0.07%, 2ppm/°C
GAIN SET WITH EXT. RESISTORS FOR > 5V/V
HIGH CMRR: 73dB 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
MSOP-8 SINGLE AND TSSOP-14 DUAL PACKAGES
● INDUSTRIAL SENSOR AMPLIFIERS:
Bridge, RTD, Thermocouple, Position
● PHYSIOLOGICAL AMPLIFIERS: ECG, EEG, EMG
● A/D CONVERTER SIGNAL CONDITIONING
● DIFFERENTIAL LINE RECEIVERS WITH GAIN
● FIELD UTILITY METERS
● PCMCIA CARDS
● AUDIO AMPLIFIERS
● COMMUNICATION SYSTEMS
● TEST EQUIPMENT
● AUTOMOTIVE INSTRUMENTATION
DESCRIPTION
The INA332 rejects line noise and its harmonics because
common-mode error remains low even at higher frequencies.
The INA332 and INA2332 are rail-to-rail output, low-power
CMOS instrumentation amplifiers that offer wide range, singlesupply, and bipolar-supply operation. Using a special manufacturing flow, the INA332 family provides the lowest cost
available, while still achieving low-noise amplification of differential signals with 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
multichannel applications.
Configured internally in a gain of 5V/V, the INA332 offers
flexibility in higher gains by choosing external resistors.
High bandwidth and slew rate make the INA332 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
INA332 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, the INA331 family can be used in demanding
industrial and automotive environments.
R2
R1
RG
G = 5 + (5R2/R1)
INA2332
40kΩ
INA332
10kΩ
VREF
40kΩ
Ch A
10kΩ
A1
A3
VOUT
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.
Copyright © 2001, 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
ELECTROSTATIC
DISCHARGE SENSITIVITY
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 .................................................. –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 Instruments recommends that all integrated circuits be handled with
appropriate precautions. Failure to observe proper handling
and installation procedures can cause damage.
NOTES: (1) Stresses above these ratings may cause permanent damage.
Exposure to absolute maximum conditions for extended periods may degrade
device reliability. (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.
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
PACKAGE-LEAD
PACKAGE
DESIGNATOR(1)
TEMPERATURE
RANGE
SPECIFIED
PACKAGE
MARKING
ORDERING
NUMBER
TRANSPORT
MEDIA, QUANTITY
INA332IDGK
MSOP-8
DGK
–55°C to +125°C
B32
INA332IDGKT
Tape and Reel, 250
"
"
"
"
"
INA332IDGKR
Tape and Reel, 2500
INA2332AIPW
TSSOP-14
PW
–55°C to +125°C
2332A
INA2332AIPWT
Tape and Reel, 250
"
"
"
"
"
INA2332AIPWR
Tape and Reel, 2500
PRODUCT
Single
Dual
NOTE: (1) For the most current specifications and package information, refer to our web site at www.ti.com.
PIN CONFIGURATION
Top View
INA2332
INA332
RG
1
8
Shutdown
VIN–
2
7
V+
VIN+
3
6
VOUT
V–
4
5
REF
MSOP-8 (DGK)
RGA
1
14
Shutdown A
VIN–A
2
13
VOUTA
VIN+A
3
12
REFA
V–
4
11
V+
VIN+B
5
10
REFB
VIN–B
6
9
VOUTB
RGB
7
8
Shutdown B
Dual, TSSOP-14 (PW)
2
INA332, INA2332
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SBOS216A
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 VCM = VS /2, unless otherwise noted.
INA332AIDGK
INA2332AIPW
PARAMETER
INPUT
Input Offset Voltage, RTI
Over Temperature
Temperature Coefficient
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
TYP
VS = +5V
±2
VS = +2.7V to +5.5V
±5
±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
NOISE, RTI
Voltage Noise: f = 10Hz
f = 100Hz
f = 1kHz
f = 0.1Hz to 10Hz
Current Noise: f = 1kHz
UNITS
±8
mV
mV
µV/°C
µV/V
µV/V
µV/month
Ω || pF
V
V
dB
dB
dB
dB
±9
±250
±260
1.5
3.8
73
73
114
Crosstalk, Dual
INPUT BIAS CURRENT
Bias Current
Offset Current
MAX
VCM = VS/2
±0.5
±0.5
IB
IOS
±10
±10
pA
pA
RS = 0Ω
eN
280
96
46
7
0.5
iN
nV/√Hz
nV/√Hz
nV/√Hz
µVp-p
fA/√Hz
GAIN(1)
Gain Equation, Externally Set
Range of Gain
Gain Error
vs Temperature
Nonlinearity
Over Temperature
G>5
FREQUENCY RESPONSE
Bandwidth, –3dB
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
TEMPERATURE RANGE
Specified Range
Operating/Storage Range
Thermal Resistance
±0.07
±2
±0.001
±0.002
G=5
G = 25, VS = 5V, VO = 0.05 to 4.95
OUTPUT
Output Voltage Swing from Rail(2)
Over Temperature
Capacitance Load Drive
Short-Circuit Current
G = 5 + 5(R2/R1)
5
G ≥ 10
50
1000
±0.4
±10
±0.010
±0.015
25
mV
See Typical Characteristics(3)
+48/–32
mV
pF
mA
2.0
5
1.7
2.5
2
MHz
V/µs
µs
µs
µs
50
ISC
BW
SR
tS
G = 25
VS = 5V, G = 25
G = 25, CL = 100pF, VO = 2V step
50% Input Overload G = 25
+2.7
+5.5
IQ
VSD > 2.5(4)
+2.5 to +5.5
415
ISD
VSD < 0.8(4)
0.01
–55
–65
θJA
MSOP-8, TSSOP-14 Surface Mount
V/V
%
ppm/°C
% of FS
% of FS
490
600
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 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.”
INA332, INA2332
SBOS216A
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3
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
120
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
10M
10
100
Frequency (Hz)
POWER-SUPPLY REJECTION RATIO
vs FREQUENCY
Maximum Output Voltage (Vp-p)
90
80
70
PSRR (dB)
10k
100k
MAXIMUM OUTPUT VOLTAGE vs FREQUENCY
6
100
60
50
40
30
20
10
0
VS = 5.5V
5
VS = 5.0V
4
3
VS = 2.7V
2
1
0
1
10
100
1k
10k
100
100k
10
100
1
10
100
1k
100k
1M
10M
10k
0.1
100k
2µV/div
1k
INOISE (fA/√Hz)
100
10
10k
0.1Hz TO 10Hz VOLTAGE NOISE
NOISE vs FREQUENCY
10k
1
1k
Frequency (Hz)
Frequency (Hz)
VNOISE (nV/√Hz)
1k
Frequency (Hz)
1s/div
Frequency (Hz)
4
INA332, INA2332
www.ti.com
SBOS216A
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
Output—Referred to Ground (V)
6
Swing to Rail (mV)
20
15
To Positive Rail
10
To Negative Rail
5
5
Outside of Normal Operation
4
3
REF
Increasing
2
1
0
0
0
10k
20k
30k
40k
0
50k
1
QUIESCENT CURRENT AND SHUTDOWN CURRENT
vs POWER SUPPLY
IQ
350
300
IQ (µA)
IQ (µA), ISD (nA)
400
250
200
150
100
50
ISD
0
2.5
3
3.5
4
4.5
5
600
550
500
450
400
350
300
250
200
150
100
50
0
5
5.5
IQ
ISD
–75
–50
–25
Supply Voltage (V)
0
25
50
75
100
125
150
Temperature (°C)
SHORT-CIRCUIT CURRENT vs POWER SUPPLY
SHORT-CIRCUIT CURRENT vs TEMPERATURE
60
60
ISC+
50
ISC+
50
40
40
ISC–
ISC (mA)
ISC (mA)
4
3
QUIESCENT CURRENT AND SHUTDOWN CURRENT
vs TEMPERATURE
500
450
2
Input Common-Mode Voltage (V)
RLOAD (Ω)
30
ISC–
30
20
20
10
10
0
0
2.5
3
3.5
4
4.5
5
5.5
–75
Supply Voltage (V)
–25
0
25
50
75
100
125
150
Temperature (°C)
INA332, INA2332
SBOS216A
–50
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5
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 = 100)
50mV/div
100mV/div
SMALL-SIGNAL STEP RESPONSE (G = 5)
4µs/div
SMALL-SIGNAL STEP RESPONSE
(G = 5, CL = 1000pF)
SMALL-SIGNAL STEP RESPONSE
(G = 100, CL = 1000pF)
50mV/div
100mV/div
4µs/div
10µs/div
SMALL-SIGNAL STEP RESPONSE
(G = 100, CL = 4700pF)
LARGE-SIGNAL STEP RESPONSE (G = 25)
1V/div
50mV/div
4µs/div
10µs/div
6
10µs/div
INA332, INA2332
www.ti.com
SBOS216A
TYPICAL CHARACTERISTICS (Cont.)
At TA = +25°C, VS = 5V, VCM = VS /2, RL = 10kΩ, and CL = 100pF, unless otherwise noted.
PERCENT OVERSHOOT vs LOAD CAPACITANCE
SETTLING TIME vs GAIN
100
60
Output 2Vp-p
Differential
Input Drive
Output 100mVp-p
Differential Drive
90
80
40
Overshoot (%)
Settling Time (µs)
50
0.01%
30
20
G=5
70
60
50
40
G = 25
30
10
20
0.1%
10
0
0
1
10
100
10
1k
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
Shutdown Mode
VOUT
0.5
Part Draws Below 1µA Quiescent Current
0
2.5
3
3.5
4
4.5
5
50µs/div
5.5
Supply Voltage (V)
OFFSET VOLTAGE DRIFT
PRODUCTION DISTRIBUTION
OFFSET VOLTAGE PRODUCTION DISTRIBUTION
20
25
Percentage of Amplifiers (%)
Percentage of Amplifiers (%)
18
20
15
10
5
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
–14
–13
–11
–10
–8
–7
–6
–4
–3
–1
0
1
3
4
6
7
8
10
11
13
14
0
Offset Voltage (mV)
Offset Voltage (µV/°C)
INA332, INA2332
SBOS216A
www.ti.com
7
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
10000
Input Bias Current (pA)
7
Slew Rate (V/µs)
6
5
4
3
2
1000
100
10
1
1
0
0.1
–75
–50
–25
0
25
50
75
100
125
150
–75
–50
–25
Temperature (°C)
CHANNEL SEPARATION vs FREQUENCY
50
75
100
125
150
OUTPUT VOLTAGE SWING vs OUTPUT CURRENT
5
100
4
Output Voltage (V)
Separation (dB)
25
Temperature (°C)
120
80
60
40
3
25°C
125°C
–55°C
2
1
20
0
0
1
10
100
1k
10k
100k
1M
10M
0
Frequency (Hz)
8
0
5
10
15
20
25
30
35
40
45
50
55
60
Output Current (mA)
INA332, INA2332
www.ti.com
SBOS216A
OPERATING VOLTAGE
APPLICATIONS INFORMATION
The INA332 family is fully specified over a supply range of
+2.7V to +5.5V, with key parameters tested 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 Characteristics.
The INA332 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
INA332 and INA2332. The power supply should be capacitively decoupled with 0.1µF capacitors as close to the INA332
as possible for noisy or high-impedance applications.
The INA332 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 )
Short VOUT to RG
for G = 5
R1
DESIRED GAIN
(V/V)
R2
5
10
50
100
RG
1
5
REF
40kΩ
10kΩ
R2
R1
OPEN SHORT
100kΩ 100kΩ
10kΩ
90kΩ
10kΩ 190kΩ
40kΩ
VIN–
VIN+
10kΩ
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
INA332
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
INA332
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 Characteristics.
FIGURE 2. Single-Supply Bridge Amplifier.
INA332, INA2332
SBOS216A
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9
SETTING THE GAIN
The ratio of R2 to R1, or the impedance between pins 1, 5,
and 6, determines the gain of the INA332. With an internally
set gain of 5, the INA332 can be programmed for gains
greater than 5 according to the following equation:
G = 5 + 5 (R2/R1)
The INA332 is designed to provide accurate gain, with gain
error 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.
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.
V+
COMMON-MODE INPUT RANGE
VIN+ 3
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
8
Microphone,
Hydrophone,
etc.
REF
5
VIN– 2
47kΩ
INA332
6
VOUT
1
4
V–
RG
VB(1)
VOA1 = 5/4 VCM – 1/4 VREF
V+
(See typical characteristic “Common-Mode Input Range vs
Reference Voltage”).
VIN+ 3
8
Transformer
REF
5
INA332
6
VOUT
1
VIN– 2
REFERENCE
4
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–)
VB(1)
Bridge
Amplifier
V–
V+
The reference pin requires a low-impedance connection. As
little as 160Ω in series with the reference pin will degrade the
CMRR to 50dB. 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).
Bridge
Sensor
VIN+ 3
Shutdown
7
8
REF
5
INA332
6
VOUT
1
VIN– 2
4
V–
INPUT BIAS CURRENT RETURN
RG Bridge resistance
provides bias
current return
NOTE: (1) VB is bias voltage within
common-mode range, dependent
on REF.
With a high input impedance of 1013Ω, the INA332 is ideal for
use with high-impedance sources. The input bias current of
less than 10pA makes the INA332 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-mode
range and the input amplifier will saturate. Figure 3 shows
Center-tap
RG provides bias
current return
VEX
For ensured operation, VOA2 should be less than VDD – 1.2V.
10
Shutdown
7
FIGURE 3. Providing an Input Common-Mode Path.
INA332, INA2332
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SBOS216A
SHUTDOWN MODE
+5V
The shutdown pin of the INA332 is nominally connected to V+.
When the pin is pulled below 0.8V on a 5V supply, the INA332
goes into sleep mode within nanoseconds. For actual shutdown 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 ‘sleepmode’ the amplifier has high output impedance, making the
INA332 suitable for multiplexing.
0.1µF
VIN+
3
V+
7
5
INA332
8
REF
VIN–
0.1µF
Shutdown
6
VOUT
1
2
OPA340
VOUT
4
V–
RG
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.
For resistive loads greater than 10kΩ, the output voltage can
swing to within 25mV of the supply rail while maintaining low
gain error. For heavier loads and over temperature, see the
typical characteristic “Output Voltage Swing vs Output Current.” The INA332’s low output impedance at high frequencies
makes it suitable for directly driving Capacitive-Input A/D
converters, as shown in Figure 4.
FIGURE 5. Output Buffering Circuit. Able to drive loads as
low as 600Ω.
V+
VIN+
REF(1)
VIN–
7
5
INA332
8
V+
7
3
8
REF
VIN–
5
INA332
2
1
4
V–
6
VOUT
RG
OPA336
ADS7818
or
ADS7822
Adjustable
Voltage
12-Bits
NOTE: (1) REF should be adjusted for the desired output level.
The value of REF affects the common-mode input range.
RG
FIGURE 6. Optional Offset Trimming Voltage.
fS < 100kHz
INPUT PROTECTION
FIGURE 4. INA332 Directly Drives Capacitive-Input, HighSpeed A/D Converter.
OUTPUT BUFFERING
The INA332 is optimized for a load impedance of 10kΩ or
greater. For higher output current the INA332 can be buffered 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.
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.
OFFSET TRIMMING
V+
The INA332 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 commonmode rejection.
RLIM
3
VIN+
IOVERLOAD
10mA max
REF
5
Shutdown
7
8
INA332
6
VOUT
1
2
VIN–
4
RLIM
V–
RG
FIGURE 7. Sample Output Buffering Circuit.
INA332, INA2332
SBOS216A
VOUT
4
V–
Shutdown
6
1
2
+5V
VIN+
Shutdown
3
www.ti.com
11
OFFSET VOLTAGE ERROR CALCULATION
FEEDBACK CAPACITOR IMPROVES RESPONSE
The offset voltage (VOS) of the INA332AIDGK is specified at
a maximum of 500µV 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.
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 INA332’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 highfrequency noise.
Power-Supply Rejection Ratio (PSRR) is specified in µV/V.
For the INA332, 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:
CMRR (in µV/V) =
10[(CMRR in dB)/–20]
•
V+
VIN+
106
7
3
Shutdown
8
INA332
For the INA332, the worst case CMRR over the specified
common-mode range is 60dB (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.
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:
REF
RX
6
5
VOUT
CIN
CL
1
VIN–
2
4
RG
V–
RIN
RF
RIN • CIN = RF • CF
CF
Where CIN is equal to the INA332’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:
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.
12
Where CIN is equal to the INA332’s RG-pin input capacitance
(typically 3pF) plus the layout capacitance. The capacitor can
be varied until optimum performance is obtained.
INA332, INA2332
www.ti.com
SBOS216A
APPLICATION CIRCUITS
Filtering can be modified to suit application needs by changing the capacitor value of the output filter.
MEDICAL ECG APPLICATIONS
Figure 9 shows the INA332 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 INA332 configured to drive an
ADS7818. Functioning at frequencies of up to 500kHz, the
INA332 is ideal for low-power data acquisition.
VR
OPA336
1.6nF
0.1µF
V+
100kΩ
VIN+ 3
Left Arm
100kΩ
Right Arm
5
VIN–
2
INA332
1
10kΩ
OPA336
VOUT PUT
VR
V–
2MΩ
10kΩ
6
4
+5V
1MΩ
7
8
REF
1MΩ
Shutdown
RG
1MΩ
2MΩ
2kΩ
VR = +2.5V
2kΩ
OPA336
Right
Leg
FIGURE 9. Simplified ECG Circuit for Medical Applications.
INA332, INA2332
SBOS216A
www.ti.com
13
PACKAGE DRAWINGS
MPDS028B – JUNE 1997 – REVISED SEPTEMBER 2001
DGK (R-PDSO-G8)
PLASTIC SMALL-OUTLINE PACKAGE
0,38
0,25
0,65
8
0,08 M
5
0,15 NOM
3,05
2,95
4,98
4,78
Gage Plane
0,25
1
0°– 6°
4
3,05
2,95
0,69
0,41
Seating Plane
1,07 MAX
0,15
0,05
0,10
4073329/C 08/01
NOTES: A.
B.
C.
D.
14
All linear dimensions are in millimeters.
This drawing is subject to change without notice.
Body dimensions do not include mold flash or protrusion.
Falls within JEDEC MO-187
INA332, INA2332
www.ti.com
SBOS216A
PACKAGE DRAWINGS (Cont.)
MTSS001C – JANUARY 1995 – REVISED FEBRUARY 1999
PW (R-PDSO-G**)
PLASTIC SMALL-OUTLINE PACKAGE
14 PINS SHOWN
0,30
0,19
0,65
14
0,10 M
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
0,15
0,05
1,20 MAX
PINS **
0,10
8
14
16
20
24
28
A MAX
3,10
5,10
5,10
6,60
7,90
9,80
A MIN
2,90
4,90
4,90
6,40
7,70
9,60
DIM
4040064/F 01/97
NOTES: A.
B.
C.
D.
All linear dimensions are in millimeters.
This drawing is subject to change without notice.
Body dimensions do not include mold flash or protrusion not to exceed 0,15.
Falls within JEDEC MO-153
INA332, INA2332
SBOS216A
www.ti.com
15
PACKAGE OPTION ADDENDUM
www.ti.com
30-Mar-2005
PACKAGING INFORMATION
Orderable Device
Status (1)
Package
Type
Package
Drawing
Pins Package Eco Plan (2)
Qty
INA2332AIPWR
ACTIVE
TSSOP
PW
14
2500
TBD
CU NIPDAU
Level-3-240C-168 HR
INA2332AIPWT
ACTIVE
TSSOP
PW
14
250
TBD
CU NIPDAU
Level-3-240C-168 HR
INA332AIDGKR
ACTIVE
MSOP
DGK
8
2500
TBD
CU NIPDAU
Level-1-220C-UNLIM
INA332AIDGKT
ACTIVE
MSOP
DGK
8
250
TBD
CU NIPDAU
Level-1-220C-UNLIM
Lead/Ball Finish
MSL Peak Temp (3)
(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) 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.
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.
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Addendum-Page 1
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