EVAL-ADAS3022EDZ User Guide
UG-484
Rev. A | Page 17 of 32
SPECTRUM TAB
Figure 30 shows the FFT spectrum capture tab. This tab tests
the traditional ac characteristics of the converter and displays a
fast Fourier transform (FFT) of the results. As in the histogram
test, raw data is captured and passed to the PC where the FFT is
performed, displaying SNR, SINAD, THD, and SFDR.
To perform an ac test, apply a sinusoidal signal to the evaluation
board to any of the analog inputs IN[7:0]_I, either via test
points or P1. Very low distortion—a better than 130 dB input
signal source, such as Audio Precision)—is required to allow
true evaluation of the part. One possibility is to filter the input
signal from the ac source. There is no suggested band-pass
filter, but carefully consider the choices. Figure 30 displays the
results of the captured data.
•
The top part of the image displays the FFT results
including SNR, dynamic range, THD, SINAD, and noise
performance (see Label 1).
•
The lower part of the image displays the fundamental
frequency and amplitude in addition to the 2
nd
to 5
th
harmonics (see Label 2).
Figure 30. FFT Spectrum with FFT Results (Top) and with Spectrum Analysis Results (Bottom)
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