INA156A Burr-Brown Corporation, INA156A Datasheet - Page 10

• Manufacturer Part Number: INA156A
• Description: Single-Supply/ Rail-to-Rail Output/ CMOS INSTRUMENTATION AMPLIFIER
• Manufacturer: Burr-Brown Corporation

INPUT COMMON-MODE RANGE
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:
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 Common-
Mode Range vs Output Voltage.”
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 character-
istics, 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.
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.
RAIL-TO-RAIL OUTPUT
A class AB output stage with common-source transistors is
used to achieve rail-to-rail output. For resistive loads
greater than 10k , 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 Out-
put Current.” The INA156’s low output impedance at high
frequencies makes it suitable for directly driving Capaci-
tive Digital-to-Analog (CDAC) input A/D converters, as
shown in Figure 9.
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 on the input
pins is limited to 10mA. This is easily accomplished with
input resistors R
signals are inherently current-limited to less than 10mA.
Therefore, a limiting resistor is not required.
V
OUTA1
®
INA156
LIM
= –
, as shown in Figure 8. Many input
1
/
9
V
REF
+ (1 +
The INA156 can be
1
/
9
) V
IN
–
(2)
10
FIGURE 7. Single-Supply, High-Side Current Monitor.
FIGURE 9. Driving Capacitive-Input A/D Converter.
FIGURE 6. Input Offset Voltage Changes with Common-
FIGURE 8. Input Current Protection for Voltages Exceed-
–1
–2
–3
–4
–5
0.02
5
4
3
2
1
0
0.0
2.5A
V
1
8
Load
2
3
S
V+
0.5 1.0
= 5.5V
Mode Voltage.
ing the Supply Voltage.
10mA max
I
I
INA156
OVERLOAD
L
R
R
5
LIM
LIM
50mV
7
P-Channel Operation
Input Common-Mode Voltage (V)
1.5 2.0
4
+5V
6
NOTE: Output is referred to V+.
2.5 3.0
NOTE: G = 10 configuration
1
8
2
3
2
3
1
8
INA156
ADS7818
ADS7834
V
Ref
INA156
Pins 1 and 8 Open
REF
3.5 4.0 4.5
or
5
5
G = 10
Transistion
f
Region
SAMPLE
7
4
6
12-Bits
6
= 500kHz
N-Channel
Operation
5.0
V
OUT
5.5