INA155 datasheet(9/16 Pages) TI

9 / 16 page

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 VS/2. This must be a low-imped-

ance connection to ensure good common-mode rejection. A

resistance of 200

Ω 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 20

Ω 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

REF

(1)

+5V

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.

–

Ref

22.2k

Ω

200k

Ω

Gain Pins Open:

G = 10

External Resistor R

10 < G < 50

Gain Pins Connected:

G = 50

Ω

200k

Ω

22.2k

Ω

V–

0.1

µF

Single Supply

Also drawn in simplified form:

Dual Supply

INA155

OUT

Ref

0.1

µF

V+

V–

DESIRED GAIN

(V/V)

(

Ω)

Open

30k

10k

3.3k

Short

G = 10 +

400k

Ω

10k

Ω + R

–

OUT = (VIN – VIN) • G + VREF

+–

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