INA155EA BURR-BROWN [Burr-Brown Corporation], INA155EA Datasheet - Page 11

• Manufacturer Part Number: INA155EA
• Description: Single-Supply, Rail-to-Rail Output, CMOS INSTRUMENTATION AMPLIFIER
• Manufacturer: BURR-BROWN [Burr-Brown Corporation]

INPUT COMMON-MODE RANGE
The input common-mode range of the INA155 for various
operating conditions is shown the in 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:
Using this equation given that the output of A1 can swing to
within 10mV of either rail, the input common-mode voltage
range can be calculated. 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 Com-
mon-Mode Range vs Output Voltage.”
INPUT RANGE FOR BEST ACCURACY
The internal amplifiers have rail-to-rail input stages, achieved
by using complementary n- 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+) – 0.8V. Due to these charac-
teristics operating the INA155 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 INA155 can be
operated below or above the transition region with excellent
results. Figure 7 demonstrates the use of the INA155 in a
single-supply, high-side current monitor. In this applica-
tion, the INA155 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 INA155’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
LIM
= –
as shown in Figure 8. Many input
1
/
9
V
REF
+ (1 +
1
/
9
) V
IN
–
(2)
11
FIGURE 7. Single-Supply, High-Side Current Monitor.
FIGURE 9. INA155 Directly Drives Capacitive-Input,
FIGURE 6. Input Offset Voltage Changes with Common-
FIGURE 8. Input Current Protection for Voltages Exceed-
–0.100
0.02
–0.20
–0.40
–0.60
–0.80
1.00
0.80
0.60
0.40
0.20
0.00
2.5A
1
8
3
Load
2
0.0
V+
High-Speed A/D Converter.
Mode Voltage.
ing the Supply Voltage.
10mA max
V
I
I
INA155
S
OVERLOAD
0.5 1.0
L
R
R
= 5.5V
4
LIM
LIM
50mV
7
4
P-Channel Operation
Input Common-Mode Voltage (V)
1.5 2.0
+5V
6
NOTE: Output is referred to V+.
NOTE: G = 10 configuration
1
8
3
2
2
3
2.5
1
8
V
S
INA155
INA155
= –1.8V
V
ADS7818
ADS7834
V
INA155
Pins 1 and 8 Open
REF
3.0
S
= –0.8V
5
or
5
3.5
G = 10
f
SAMPLE
7
4
Transistion
4.0
6
Region
12-Bits
6
= 500kHz
4.5 5.0
V
OUT
N-Channel
Operation
5.5
®