BB INA156E

®
INA156
INA
156
For most current data sheet and other product
information, visit www.burr-brown.com
Single-Supply, Rail-to-Rail Output, CMOS
INSTRUMENTATION AMPLIFIER
FEATURES
APPLICATIONS
●
●
●
●
● INDUSTRIAL SENSOR AMPLIFIERS:
Bridge, RTD, Thermocouple, Flow, Position
● MEDICAL EQUIPMENT:
ECG, EEG, EMG Amplifiers
● DRIVING A/D CONVERTERS
● PCMCIA CARDS
● AUDIO PROCESSING
● COMMUNICATIONS
● TEST EQUIPMENT
● LOW COST AUTOMOTIVE INSTRUMENTATION
●
●
●
●
●
RAIL-TO-RAIL OUTPUT SWING: Within 20mV
LOW OFFSET DRIFT: ±5µV/°C
INTERNAL FIXED GAIN = 10V/V OR 50V/V
SPECIFIED TEMPERATURE RANGE:
–55°C to +125°C
LOW INPUT BIAS CURRENT: 1pA
WIDE BANDWIDTH: 550kHz in G = 10
HIGH SLEW RATE: 6.5V/µs
LOW COST
TINY MSOP-8 PACKAGES
DESCRIPTION
The INA156 is a low-cost CMOS instrumentation
amplifier with rail-to-rail output swing optimized for
low-voltage, single-supply operation.
Wide bandwidth (550kHz in G = 10) and high slew
rate (6.5V/µs) make the INA156 suitable for driving
sampling A/D converters as well as general purpose
and audio applications. Fast settling time allows use
with higher speed sensors and transducers, and rapid
scanning data acquisition systems.
RG
Gain can be set to 10V/V or 50V/V by pin strapping.
Gains between these two values can be obtained with
the addition of a single resistor. The INA156 is fully
specified over the supply range of +2.7V to +5.5V.
The INA156 is available in an MSOP-8 surface-mount
package specified for operation over the temperature
range –55°C to 125°C.
G = 10 pins open
G = 50 pins connected
1
V+
RG
8
7
INA156
5kΩ
Ref
5
200kΩ
5kΩ
22.2kΩ
22.2kΩ
200kΩ
+
–
VO = (VIN – VIN) • G + VREF
–
VIN
2
V+
3
A1
6
A2
VO
IN
4
V–
International Airport Industrial Park • Mailing Address: PO Box 11400, Tucson, AZ 85734 • Street Address: 6730 S. Tucson Blvd., Tucson, AZ 85706 • Tel: (520) 746-1111
Twx: 910-952-1111 • Internet: http://www.burr-brown.com/ • Cable: BBRCORP • Telex: 066-6491 • FAX: (520) 889-1510 • Immediate Product Info: (800) 548-6132
©1999 Burr-Brown Corporation
PDS-1565A
Printed in U.S.A. December, 1999
SPECIFICATIONS: 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 connected to VS/2. RG pins open (G = 10), and Ref = VS /2, unless otherwise noted.
INA156E, A
PARAMETER
CONDITION
INPUT
Offset Voltage, RTI
Over Temperature
Drift
vs Power Supply
Over Temperature
vs Time
VOS
dVOS/dT
PSRR
MIN
TYP
VS = +5.0V, VCM = VS/2
±2.5
VS = +2.7V to +6V, VCM = 0.2 • VS
±5
±50
±0.4
MAX
UNITS
±8
mV
mV
µV/°C
µV/V
µV/V
µV/mo
±9
±200
±250
INPUT VOLTAGE RANGE
Safe Input Voltage
Common-Mode Range(1)
Common-Mode Rejection Ratio
Over Temperature
VCM
CMRR
VS = 5.5V
VS = 2.7V
VS = 5.5V, 0.6V < VCM < 3.7V, G = 10
VS = 5.5V, 0.6V < VCM < 3.7V, G = 50
Over Temperature
(V–) – 0.5
0.3
0.2
66
65
74
73
INPUT IMPEDANCE
Differential
Common-Mode
(V+) + 0.5
5.2(2)
2.5(2)
78
87
Ω || pF
Ω || pF
1013 || 3
1013 || 3
INPUT BIAS CURRENT
Input Bias Current
Offset Current
±1
±1
IB
IOS
10
VS = 5.5V, VO = 0.02V to 5.48V, G = 10
VS = 5.5V, VO = 0.05V to 5.45V, G = 50
vs Temperature
Nonlinearity
Over Temperature
VS = 5.5V, G = 10 or 50
OUTPUT
Voltage Output Swing from Rail
Over Temperature
Short-Circuit Current
Capacitance Load (stable operation)
FREQUENCY RESPONSE
Bandwidth, –3dB
BW
Slew Rate
Settling Time: 0.1%
SR
tS
0.01%
TEMPERATURE RANGE
Specified Range
Operating Range
Storage Range
Thermal Resistance
MSOP-8 Surface Mount
SO-8 Surface Mount
5
Short-Circuit to Ground
±50
See Typical Curve
G = 10
G = 50
VS = 5.5V, CL = 100pF
VS = 5.5V, VO = 2V Step, CL = 100pF, G = 10
VS = 5.5V, VO = 2V Step, CL = 100pF, G = 50
VS = 5.5V, VO = 2V Step, CL = 100pF, G = 10
VS = 5.5V, VO = 2V Step, CL = 100pF, G = 50
50% Input Overload
550
110
6.5
5
11
8
15
0.2
See Typical Curve
THD+N
POWER SUPPLY
Specified Voltage Range
Operating Voltage Range
Quiescent Current
Over Temperature
50
G = 10 + 400kΩ/(10kΩ + RG) V/V
±0.08
±0.4
±2
±10
±0.1
±0.8
±15
±30
±0.005
±0.015
±0.015
G = 10, RL = 10kΩ, GERR < 0.4%
+2.7
VIN = 0, IO = 0
VIN = 0, IO = 0
20
20
–55
–65
–65
θJA
150
150
V/V
%
ppm/°C
%
ppm/°C
% of FSR
% of FSR
mV
mV
mA
kHz
kHz
V/µs
µs
µs
µs
µs
µs
+5.5
+2.5 to +6
1.8
pA
pA
µV/Vp-p
nV/√Hz
nV/√Hz
nV/√Hz
fA/√Hz
4.5
260
99
40
2
GAIN
Gain Equation
Gain Error(3)
vs Temperature
Overload Recovery
Total Harmonic Distortion + Noise
±10
±10
RS = 0Ω, G = 10 or 50
NOISE, RTI
Voltage Noise: f = 0.1Hz to 10Hz
Voltage Noise Density: f = 10Hz
f = 100Hz
f = 1kHz
Current Noise: f = 1kHz
V
V
V
dB
dB
dB
dB
2.5
3.2
V
V
mA
mA
+125
+150
+150
°C
°C
°C
°C/W
°C/W
NOTES: (1) For further information, refer to typical performance curves on common-mode input range. (2) Operation beyond (V+) – 1.8V (max) results in reduced common-mode
rejection. See discussion and Figure 6 in the text of this data sheet. (3) Does not include error and TCR of additional optional gain-setting resistor in series with RG, if used.
®
INA156
2
ELECTROSTATIC
DISCHARGE SENSITIVITY
PIN CONFIGURATION
Top View
MSOP
RG
1
8
RG
–
VIN
2
V+
7
V+
IN
3
6
VOUT
V–
4
5
Ref
This integrated circuit can be damaged by ESD. Burr-Brown
recommends that all integrated circuits be handled with
appropriate precautions. Failure to observe proper handling
and installation procedures can cause damage.
INA156
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.
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
Lead Temperature (soldering, 10s) ............................................... +300°C
NOTES: (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 that 0.5V beyond the supply rails should be current limited
to 10mA or less. (3) Short circuit to ground.
PACKAGE/ORDERING INFORMATION
PRODUCT
PACKAGE
PACKAGE
DRAWING
NUMBER
INA156 EA
MSOP-8
337
–55°C to +125°C
A56
"
"
"
"
"
SPECIFIED
TEMPERATURE
RANGE
PACKAGE
MARKING
ORDERING
NUMBER(1)
TRANSPORT
MEDIA
INA156EA/250
INA156EA/2K5
Tape and Reel
Tape and Reel
NOTE: (1) Models with a slash (/) are available only in Tape and Reel in the quantities indicated (e.g., /2K5 indicates 2500 devices per reel). Ordering 2500 pieces
of “INA156EA/2K5” will get a single 2500-piece Tape and Reel.
The information provided herein is believed to be reliable; however, BURR-BROWN assumes no responsibility for inaccuracies or omissions. BURR-BROWN assumes
no responsibility for the use of this information, and all use of such information shall be entirely at the user’s own risk. Prices and specifications are subject to change
without notice. No patent rights or licenses to any of the circuits described herein are implied or granted to any third party. BURR-BROWN does not authorize or warrant
any BURR-BROWN product for use in life support devices and/or systems.
®
3
INA156
TYPICAL PERFORMANCE CURVES
At TA = +25°C, VS = 5.5V, RL = 10kΩ connected to VS/2. RG pins open (G = 10), and Ref = VS /2, unless otherwise noted.
GAIN vs FREQUENCY
COMMON-MODE REJECTION RATIO vs FREQUENCY
40
100
35
90
30
G = 50
80
G = 50
G = 10
70
20
G =10
15
60
CMRR (dB)
Gain (dB)
25
50
40
30
10
20
5
10
0
0
1
10
100
1k
10k
100k
1M
10M
0.1
1
10
100
Frequency (Hz)
100k
6
Maximum Output Voltage (Vp-p)
90
80
70
60
50
40
30
20
10
5
4
3
2
1
VS = 5.5V
0
0
1
10
100
1k
10k
100k
1
1M
10
100
1k
10k
100k
1M
Frequency (Hz)
Frequency (Hz)
SHORT-CIRCUIT CURRENT AND QUIESCENT CURRENT
vs POWER SUPPLY
QUIESCENT CURRENT AND SHORT-CIRCUIT CURRENT
vs TEMPERATURE
100
2.1
55
–ISC
50
2.5
IQ
–ISC
2.0
80
2.0
+ISC
+ISC
40
1.8
35
1.7
30
1.6
2.5
3
3.5
4.5
4.0
Supply Voltage (V)
5
5.5
1.5
40
1.0
20
0.5
0
75
6
®
INA156
60
0
1.5
25
ISC (mA)
IQ
IQ (mA)
1.9
45
4
–50
–25
0
25
50
75
Temperature (°C)
100
125
150
IQ (mA)
PSRR (dB)
10k
MAXIMUM OUTPUT VOLTAGE vs FREQUENCY
POWER SUPPLY REJECTION RATIO vs FREQUENCY
100
ISC (mA)
1k
Frequency (Hz)
TYPICAL PERFORMANCE CURVES
(Cont.)
At TA = +25°C, VS = 5.5V, RL = 10kΩ connected to VS/2. RG pins open (G = 10), and Ref = VS /2, unless otherwise noted.
TOTAL HARMONIC DISTORTION + NOISE
vs FREQUENCY
INPUT VOLTAGE AND CURRENT NOISE DENSITY
vs FREQUENCY
10k
1
100
10
in
100
1
RL = 2kΩ
0.1
THD+N (%)
1k
Current Noise (fA/√Hz)
Voltage Noise (nV/√Hz)
RL = 600Ω
en
G = 50
RL = 600Ω
RL = 10kΩ
0.01
G = 10
RL = 2kΩ
10
0.1
10
1
100
1k
10k
RL =10kΩ
0.001
0.1
100k
10
100
1k
10k
Frequency (Hz)
Frequency (Hz)
0.1Hz TO 10Hz VOLTAGE NOISE
INPUT BIAS CURRENT vs TEMPERATURE
10k
1µV/div
Input Bias Current (pA)
1k
100
10
1
Input-Referred
0.1
–75
500ms/div
–50
–25
0
25
50
75
100
125
150
125
150
Temperature (°C)
SLEW RATE vs POWER SUPPLY
SLEW RATE vs TEMPERATURE
7
10
9
8
6
Slew Rate (V/µs)
Slew Rate (Vµs)
6.5
5.5
5
7
6
5
4
3
2
4.5
1
4
0
2.5
3
3.5
4
4.5
5
5.5
6
75
Supply Voltage (V)
–50
–25
0
25
50
75
100
Temperature (°C)
®
5
INA156
TYPICAL PERFORMANCE CURVES
(Cont.)
At TA = +25°C, VS = 5.5V, RL = 10kΩ connected to VS/2. RG pins open (G = 10), and Ref = VS /2, unless otherwise noted.
OFFSET VOLTAGE DRIFT
PRODUCTION DISTRIBUTION
18
16
16
14
14
Percent of Amplifiers (%)
18
12
10
8
6
4
12
10
8
6
4
–20
–18
–16
–14
–12
–10
–8
–6
–4
–2
0
2
4
6
8
10
12
14
16
18
20
10
8
6
4
2
0
–2
–4
0
–6
2
0
–8
2
–10
Production Distribution (%)
VOS TYPICAL
PRODUCTION DISTRIBUTION
Offset Voltage (mV)
Offset Voltage Drift (µV/°C)
OVERSHOOT vs LOAD CAPACITANCE
SETTLING TIME vs LOAD CAPACITANCE
60
20
18
12
Overshoot (%)
14
0.1%, G = 50
10
0.01%, G = 10
8
6
0.1%, G = 10
40
G = 10
30
20
G = 50
4
10
2
0
0
10
100
1k
10
10k
100
1k
Load Capacitance (pF)
Load Capacitance (pF)
SMALL-SIGNAL STEP RESPONSE
G = 10, CL = 100pF, RL = 10kΩ
SMALL-SIGNAL STEP RESPONSE
G = 50, CL = 100pF, RL = 10kΩ
100mV/div
100mV/div
Settling Time (µs)
50
0.01%, G = 50
16
5µs/div
5µs/div
®
INA156
6
10k
TYPICAL PERFORMANCE CURVES
(Cont.)
At TA = +25°C, VS = 5.5V, RL = 10kΩ connected to VS/2. RG pins open (G = 10), and Ref = VS /2, unless otherwise noted.
LARGE-SIGNAL STEP RESPONSE
G = 10, G = 50, CL = 100pF, RL = 10kΩ
OUTPUT VOLTAGE SWING vs OUTPUT CURRENT
5
1V/div
Output Voltage (V)
4
+125°C
–55°C
+25°C
3
2
+125°C
–55°C
+25°C
1
0
0
1µs/div
10
20
50
60
70
80
90
100
INPUT COMMON-MODE RANGE
vs OUTPUT VOLTAGE, G = 50
6
6
G = 50
G = 10
5
5
4
4
VCM (V)
VCM (V)
40
Output Current (mA)
INPUT COMMON-MODE RANGE
vs REFERENCE VOLTAGE, G = 10
3
2
3
Ref = 0V
Ref = 2.75V
Ref = 5.5V
2
0.9V– + 0.1Ref < VCM < 0.9V+ + 0.1Ref
1
0.9V– + 0.04VOUT + 0.06Ref < VCM < 0.9V+ + 0.04VOUT + 0.06Ref
1
0
0
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
5.5
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
VREF (V)
VOUT (V)
COMMON-MODE REJECTION RATIO
PRODUCTION DISTRIBUTION
COMMON-MODE REJECTION RATIO
PRODUCTION DISTRIBUTION
9
5
5.5
10
80dB
9
8
Production Distribution (%)
G = 10
7
6
5
4
3
2
80dB
G = 50
8
7
6
5
4
3
2
1
0
0
–200
–180
–160
–140
–120
–100
–80
–60
–40
–20
0
20
40
60
80
100
120
140
160
180
200
1
–500
–450
–400
–350
–300
–250
–200
–150
–100
–50
0
50
100
150
200
250
300
350
400
450
500
Production Distribution (%)
30
CMRR (µV/V)
CMRR (µV/V)
®
7
INA156
APPLICATIONS INFORMATION
OPERATING VOLTAGE
Figure 1 shows the basic connections required for operation
of the INA156. Applications with noisy or high impedance
power supplies may require decoupling capacitors close to
the device pins, as shown.
The INA156 is fully specified and guaranteed over the supply
range +2.7V to +5.5V, with key parameters guaranteed over
the temperature range of –55°C to +125°C. Parameters that
vary significantly with operating voltages, load conditions or
temperature are shown in the Typical Performance Curves.
The output is referred to the output reference terminal, Ref,
which is normally set to VS/2. This must be a low-impedance connection to ensure good common-mode rejection.
The INA156 can be operated from either single or dual
power supplies. By adjusting the voltage applied to the
reference terminal, the input common-mode voltage range
and the output range can be adjusted within the bounds
shown in the Typical Performance Curves. Figure 2 shows
a bridge amplifier circuit operated from a single +5V power
supply. The bridge provides a relatively small differential
voltage on top of an input common-mode voltage near 2.5V.
In addition, for the G = 50 configuration, the connection
between pins 1 and 8 must be low-impedance. A connection
impedance of 20Ω can cause a 0.2% shift in gain error.
External Resistor RG:
10 < G < 50
V+
Gain Pins Connected:
G = 50
0.1µF
Gain Pins Open:
G = 10
1
7
G = 10 +
8
200kΩ
5
22.2kΩ
22.2kΩ
10
20
30
40
50
Open
30k
10k
3.3k
Short
200kΩ
6
A2
3
V+
RG
(Ω)
A1
2
–
VIN
DESIRED GAIN
(V/V)
5kΩ
5kΩ
Ref
400kΩ
10kΩ + RG
+
–
– VIN
) • G + VREF
VOUT = (VIN
IN
Also drawn in simplified form:
V+
INA156
4
+
VIN
3
1
0.1µF
Single Supply
–
VIN
Dual Supply
7
4
V–
V–
VOUT
5
8
2
6
INA156
Ref
FIGURE 1. Basic Connections.
+5V
Bridge
Sensor
(2)
+
VIN
3
1
–
VIN
7
INA156
VOUT = 0.01V to 4.99V
4
8
2
6
5
NOTES: (1) VREF should be adjusted for the desired output level,
keeping in mind that the value of VREF affects the common-mode
input range. See Typical Performance Curves. (2) For best
performance, the common-mode input voltage should be kept away
from the transition range of (V+) – 1.8V to (V+) – 0.8V.
VREF(1)
FIGURE 2. Single-Supply Bridge Amplifier.
®
INA156
8
SETTING THE GAIN
INPUT BIAS CURRENT RETURN
Gain of 10 is achieved simply by leaving the two gain pins
(1 and 8) open. Gain of 50 is achieved by connecting the
gain pins together directly. In the G = 10 configuration, the
gain error is less than 0.4%. In the G = 50 configuration, the
gain error is less than 0.8%.
The input impedance of the INA156 is extremely high—
approximately 1013Ω, making it ideal for use with high-impedance sources. However, a path must be provided for the input
bias current of both inputs. This input bias current is less than
10pA and is virtually independent of the input voltage.
Gain can be set to any value between 10 and 50 by connecting a resistor RG between the gain pins according to the
following equation:
Input circuitry must provide a path for this input bias current
for proper operation. Figure 5 shows various provisions for
an input bias current path. Without a bias current path, the
inputs will float to a potential that exceeds the commonmode range and the input amplifier will saturate.
10 + 400kΩ/(10kΩ + RG)
(1)
This is demonstrated in Figure 1 and is shown with the commonly used gains and resistor RG values. However, because the
absolute value of internal resistors is not guaranteed, using the
INA156 in this configuration will increase the gain error and
gain drift with temperature, as shown in Figure 3.
2.0
400
360
Gain Drift
1.6
320
1.4
280
1.2
250
1.0
200
0.8
160
Gain Error
0.6
120
0.4
80
0.2
40
0
3
Gain Drift (ppm/°C)
1.8
Gain Error (%)
If the differential source resistance is low, the bias current
return path can be connected to one input (see the thermocouple in Figure 5). With higher source impedance, using
two equal resistors provides a balanced input with advantages of lower input offset voltage due to bias current and
better high-frequency common-mode rejection.
1
Microphone,
Hydrophone, etc.
6
INA156
8
2
47kΩ
5
47kΩ
VREF
0
10
15
25
20
30
35
40
45
50
Gain (V/V)
3
FIGURE 3. Typical Gain Error and Gain Error Drift with
External Resistor.
1
Thermocouple
8
OFFSET TRIMMING
2
Offset voltage can be adjusted by applying a correction
voltage to the reference terminal. Figure 4 shows an optional
circuit for trimming the output offset voltage. The voltage
applied to the Ref terminal is added to the output signal. An
op amp buffer is used to provide low impedance at the Ref
terminal to preserve good common-mode rejection.
VREF
V –(2)
IN
6
INA156
8
2
6
INA156
8
2
Low-resistance
thermocouple
provides bias
current return.
3
3
1
5
10kΩ
1
+(2)
VIN
6
INA156
VO
5
VREF
Center-tap
provides bias
current return
(1)
5
Ref
OPA336
Bridge
Sensor
3
1
Adjustable
Voltage
6
INA156
8
2
NOTES: (1) VREF should be adjusted for the desired output
level. The value of VREF affects the common-mode input
range. (2) For best performance, common-mode input voltage
should be less than (V+) – 1.8V or greater than (V+) – 0.8V.
5
VREF
FIGURE 4. Optional Trimming of Output Offset Voltage.
Bridge resistance
provides bias
current return
FIGURE 5. Providing an Input Common-Mode Current Path.
®
9
INA156
INPUT COMMON-MODE RANGE
5
The input common-mode range of the INA156 for various
operating conditions is shown in the Typical Performance
Curves. The common-mode input range is limited by the
output voltage swing of A1, an internal circuit node. For the
G = 10 configuration, output voltage of A1 can be expressed as:
Input Offset Voltage (mV)
VOUTA1 = – 1/9VREF + (1 + 1/9) VIN–
(2)
The input common-mode voltage range can be calculated
using this equation, given that the output of A1 can swing to
within 20mV of either rail. When the input common-mode
range is exceeded (A1’s output is saturated), A2 can still be in
linear operation and respond to changes in the non-inverting
input voltage. However, the output voltage will be invalid.
The common-mode range for the G = 50 configuration is
included in the typical performance curve, “Input CommonMode Range vs Output Voltage.”
3
2
1
0
–1
–2
–3
–4
VS = 5.5V
–5
0.0
0.5
1.5
1.0
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
Input Common-Mode Voltage (V)
FIGURE 6. Input Offset Voltage Changes with CommonMode Voltage.
V+
NOTE: Output is referred to V+.
INPUT RANGE FOR BEST ACCURACY
The internal amplifiers have rail-to-rail input stages, achieved
by using complementary n-channel and p-channel input
pairs. The common-mode input voltage determines whether
the p-channel or the n-channel input stage is operating. The
transition between the input stages is gradual and occurs
between (V+) – 1.8V to (V+) – 1V. Due to these characteristics, operating the INA156 with input voltages within the
transition region of (V+) – 1.8V to (V+) – 0.8V results in a
shift in input offset voltage, and reduced common-mode and
power supply rejection performance. Typical patterns of the
offset voltage change throughout the input common-mode
range are illustrated in Figure 6. The INA156 can be
operated below or above the transition region with excellent
results. Figure 7 demonstrates the use of the INA156 in a
single-supply, high-side current monitor. In this application,
the INA156 is operated above the transition region.
Ref
2
5
7
0.02Ω
1
50mV
6
INA156
4
8
3
IL
2.5A
Load
G = 10
Pins 1 and 8 Open
FIGURE 7. Single-Supply, High-Side Current Monitor.
RLIM
RAIL-TO-RAIL OUTPUT
3
IOVERLOAD
10mA max
A class AB output stage with common-source transistors is
used to achieve rail-to-rail output. For resistive loads
greater than 10kΩ, 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 performance curve “Output Voltage Swing vs Output Current.” The INA156’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 9.
1
8
6
INA156
VOUT
5
2
RLIM
VREF
FIGURE 8. Input Current Protection for Voltages Exceeding the Supply Voltage.
+5V
INPUT PROTECTION
3
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 on the input
pins is limited to 10mA. This is easily accomplished with
input resistors RLIM, as shown in Figure 8. Many input
signals are inherently current-limited to less than 10mA.
Therefore, a limiting resistor is not required.
1
7
2
6
INA156
4
8
5
ADS7818
or
ADS7834
12-Bits
fSAMPLE = 500kHz
NOTE: G = 10 configuration
FIGURE 9. Driving Capacitive-Input A/D Converter.
®
INA156
Transistion N-Channel
Region
Operation
P-Channel Operation
4
10