INA333 datasheet(17/27 Pages) TI2

17 / 27 page

300W

+3V

150W

(1)

- D

2V+ V

INA333

Ref

1.5V

INA333-HT

www.ti.com

SBOS514C – MARCH 2010 – REVISED OCTOBER 2013

Input overload conditions can produce an output

voltage that appears normal. For example, if an input

overload condition drives both input amplifiers to the

respective positive output swing limit, the difference

voltage measured by the output amplifier is near

zero. The output of the INA333 is near 0 V even

though both inputs are overloaded.

OPERATING VOLTAGE

The INA333 operates over a power-supply range of

+1.8 V to +5.5 V (±0.9 V to ±2.75 V). Supply voltages

higher

than

(absolute

maximum)

can

(1) R1 creates proper common-mode voltage, only for low-voltage

permanently damage the device. Parameters that

operation—see the Single-Supply Operation section.

vary over supply voltage or temperature are shown in

Figure 37. Single-Supply Bridge Amplifier

the Typical Characteristics section of this data sheet.

LOW VOLTAGE OPERATION

INPUT PROTECTION

The INA333 can be operated on power supplies as

The input terminals of the INA333 are protected with

low as ±0.9 V. Most parameters vary only slightly

internal diodes connected to the power-supply rails.

throughout this supply voltage range—see the Typical

These diodes clamp the applied signal to prevent it

Characteristics section. Operation at very low supply

from damaging the input circuitry. If the input signal

voltage requires careful attention to assure that the

voltage can exceed the power supplies by more than

input voltages remain within the linear range. Voltage

0.3 V, the input signal current should be limited to

swing requirements of internal nodes limit the input

less than 10 mA to protect the internal clamp diodes.

common-mode range with low power-supply voltage.

This current limiting can generally be done with a

The Typical Characteristic curves Typical Common-

series input resistor. Some signal sources are

Mode Range vs Output Voltage (Figure 22 to

inherently current-limited and do not require limiting

Figure 25) show the range of linear operation for

resistors.

various supply voltages and gains.

GENERAL LAYOUT GUIDELINES

SINGLE-SUPPLY OPERATION

Attention

good

layout

practices

always

The INA333 can be used on single power supplies of

recommended.

Keep

traces

short

and,

when

+1.8 V to +5.5 V. Figure 37 illustrates a basic single-

possible, use a printed circuit board (PCB) ground

supply circuit. The output REF terminal is connected

plane with surface-mount components placed as

to mid-supply. Zero differential input voltage demands

close to the device pins as possible. Place a 0.1-

μF

an output voltage of mid-supply. Actual output voltage

bypass capacitor closely across the supply pins.

swing is limited to approximately 50 mV above

These guidelines should be applied throughout the

ground, when the load is referred to ground as

analog circuit to improve performance and provide

shown.

The

typical

characteristic

curve

Output

benefits

such

reducing

the

electromagnetic-

Voltage Swing vs Output Current (Figure 31) shows

interference (EMI) susceptibility.

how the output voltage swing varies with output

Instrumentation amplifiers vary in the susceptibility to

current.

radio-frequency interference (RFI). RFI can generally

With single-supply operation, VIN+ and VIN– must both

be identified as a variation in offset voltage or dc

be 0.1V above ground for linear operation. For

signal levels with changes in the interfering RF signal.

instance, the inverting input cannot be connected to

The INA333 has been specifically designed to

ground to measure a voltage connected to the

minimize

susceptibility

RFI

incorporating

noninverting input.

passive RC filters with an 8-MHz corner frequency at

the VIN+ and VIN– inputs. As a result, the INA333

illustrate

the

issues

affecting

low

voltage

demonstrates remarkably low sensitivity compared to

operation, consider the circuit in Figure 37. It shows

previous generation devices. Strong RF fields may

the INA333 operating from a single 3-V supply. A

continue to cause varying offset levels, however, and

resistor in series with the low side of the bridge

may require additional shielding.

assures that the bridge output voltage is within the

common-mode range of the amplifier inputs.

APPLICATION IDEAS

Additional application ideas are shown in Figure 38 to

Figure 41.

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