Datasheet

9
®
INA155
APPLICATIONS INFORMATION
Figure 1 shows the basic connections required for operation
of the INA155. Applications with noisy or high impedance
power supplies may require decoupling capacitors close to
the device pins as shown.
The output is referred to the output reference terminal, Ref,
which is normally set to V
S
/2. This must be a low-imped-
ance connection to ensure good common-mode rejection. A
resistance of 200Ω in series with the Ref pin will cause a
typical device to degrade to approximately 80dB CMRR.
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.
OPERATING VOLTAGE
The INA155 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 INA155 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.
FIGURE 1. Basic Connections.
FIGURE 2. Single-Supply Bridge Amplifier.
Bridge
Sensor
INA155
V
REF
(1)
+5V
3
2
4
5
7
6
V
OUT
= 0.01V to 4.99V
(2)
NOTES: (1) V
REF
should be adjusted for the desired output level,
keeping in mind that the value of V
REF
affects the common-mode
input range. See Typical Performance Curve. (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.
1
8
V
IN
+
V
IN
–
Ref
22.2kΩ200kΩ
5kΩ
Gain Pins Open:
G = 10
External Resistor R
G
:
10 < G < 50
Gain Pins Connected:
G = 50
5kΩ
200kΩ22.2kΩ
4
3
2
5
7
18
V–
0.1µF
Single Supply
Also drawn in simplified form:
Dual Supply
INA155
INA155
6
1
3
8
2
V
OUT
6
7
4
5
Ref
0.1µF
V+
V+
V–
DESIRED GAIN R
G
(V/V) (Ω)
10 Open
20 30k
30 10k
40 3.3k
50 Short
G = 10 +
400kΩ
10kΩ + R
G
V
IN
–
V
IN
+
A1
A2
V
IN
+
V
IN
–
V
OUT
= (V
IN
– V
IN
) • G + V
REF
+–