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CORO

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2212

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112

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EVM Components

4 EVM Components

This section summarizes the INA827EVM components.

4.1 Power

Power is applied to the INA827 with test points V+ and V–. For the unpopulated device (U2), power is

applied using test points OAV+ and OAV–.

4.2 Inputs

Inputs are applied to the INA827 using test points V+IN and V–IN. Alternately, they can be applied by

populating the input SMA connectors (J1 and J2). The inputs for U2 are applied through test points

OAVIN+ and OAVIN–.

4.2.1 Input Filtering

R1, R2, and C1 through C3 provide the ability to apply common-mode and differential-mode filtering to the

inputs. The cutoff frequencies for the filters are shown in Equation 1 and Equation 2. It is recommended to

make C2 approximately ten times larger than C1 and C3. These calculations presume R1 = R2 and C1 =

C3.

Common-mode cutoff frequency:

(1)

Differential-mode cutoff frequency:

(2)

4.3 Outputs

The output of the INA827 can be accessed with test point VO. Alternately, it can be accessed by

populating the output SMA connector (J3).

4.3.1 Output Filtering

RO and CO provide the ability to apply a single-pole RC output filter. The cutoff frequency of the output

filter can be calculated as shown in Equation 3.

(3)

4.4 Reference

There are multiple methods of applying a reference voltage to the INA827. A straightforward approach is

to apply a voltage to the REF test point with U2 not populated. If a buffered voltage is desired, U2 can be

populated with an operational amplifier in an appropriate SO-8 package and pinout.

4.5 Prototype Area

Two prototype areas are provided for flexible evaluation. For example, they can be used to prototype a

voltage divider for a buffered reference voltage or to supply a direct reference voltage with a device such

as the REF3225.

SBOU121–June 2012 INA827EVM

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