3 EVM Components
3.1 Power
Power is applied to the INA with test points TP1 and TP11. For the unpopulated operation amplifier used for the
reference voltage circuitry (U1), power is applied using test points TP2 and TP12.
3.2 Inputs
Inputs are applied to the INA using test points TP14 and TP17 for channel A, and TP20 and TP22 for channel
B. The inputs for the op amp are applied through test points TP3 and TP13 for REFA, and TP16 and TP19
for REFB. To maintain linear operation, the INA must remain within the common mode voltage range with
respect to the power supplies and differential inputs. A useful tool to calculate whether the INA is operating
within safe limits can be found in the
TI’s Analog Engineer’s Calculator
Amplifier and
Comparators
and then click on
INA VCM v VOUT.
3.2.1 Input Filtering
Components R12, R17, and C16, C18, C21 provide the ability to apply common-mode and differential-mode
filtering to the inputs. The cutoff frequencies for the filters are shown in
approximately ten times larger than C16 and C21. These calculations presume R12 = R17 and C16 = C21. The
correlating resistors and capacitors provide input filtering for channel B.
Common-mode cutoff frequency:
(1)
Differential-mode cutoff frequency:
(2)
3.3 Output
Access the output of the device, with test point TP15 for channel A, and TP21 for channel B.
3.3.1 Output Filtering
Components R14 and C20 provide the ability to apply a single-pole RC output filter. The cutoff frequency of the
output filter is calculated as shown in
. The correlating resistor and capacitor provide output filtering
for channel B.
(3)
EVM Components
8
INA-DUAL-2AMP-EVM
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