INA821 datasheet(24/47 Pages) TI

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9.2.1.2 Detailed Design Procedure

9.2.1.2.1 Operating Voltage

The INA597 operates from single (4.5 V to 36 V) or dual (±2.25 V to ±18 V) supplies with excellent

performance. Specifications are production tested with +5-V and ±15-V supplies. Most behavior remains

unchanged throughout the full operating voltage range. Parameters that vary significantly with operating voltage

are shown in Section 7.7. The internal op amp in the INA597 is a single-supply design. This design allows linear

operation with the op amp common-mode voltage equal to, or slightly less than V– (or single-supply ground).

Although input voltages on pins 2 and 3 that are less than the negative supply voltage do not damage the

device, operation in this region is not recommended. Transient conditions at the inverting input terminal less than

the negative supply can cause a positive feedback condition that could lock the device output to the negative rail.

The INA597 accurately measures differential signals that are greater than the positive power supply. For

example with G = ½, the linear common-mode range extends to nearly three times the positive power supply

voltage; see Section 7.7, as well as Section 9.2.1.2.3.

9.2.1.2.2 Offset Voltage Trim

The INA597 is production trimmed for low offset voltage and drift. Most applications require no external offset

adjustment. Figure 9-2 shows an optional circuit for trimming the output offset voltage. The output is referred to

the output reference terminal (pin 1), which is normally grounded. A voltage applied to the REF pin is summed

with the output signal. This configuration can be used to null offset voltage. To maintain good common-mode

rejection, make sure the source impedance of a signal applied to the REF pin is less than 8 Ω. For low

impedance at the REF pin, the trim voltage can be buffered with an op amp, such as the OPA177.

INA597

O = V3 – V2

Oﬀset Adjustment

Range = ±500 µV

REF

8 W

R = 237 kW

8 W

100 kW

+15 V

–15 V

NOTE: For ±750-µV range, R = 158 k .

Figure 9-2. Offset Adjustment

INA597

SBOS385B – AUGUST 2019 – REVISED APRIL 2021

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INA821 Datasheet(PDF) 24 Page - Texas Instruments