Ac Testing-Data Capture/Fft Tab - Analog Devices EVAL-AD7492SDZ User Manual

EVAL-AD7492SDZ User Guide
AC TESTING—DATA CAPTURE/FFT TAB
Figure 19 shows the Data Capture/FFT tab This 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 the signal-to-noise ratio (SNR), signal-to-
noise-and-distortion ratio (SINAD), total harmonic distortion
(THD), and spurious-free dynamic range (SFDR). To perform
an ac test, apply a sinusoidal signal to the evaluation board at
the SMB inputs, SK1/SK3. Low distortion, better than 100 dB,
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; however, take consideration in this choice.
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Figure 19. Data Capture/FFT Tab
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Furthermore, if using a low frequency band-pass filter when the
full-scale input range is more than a few volts peak-to-peak, it is
recommended to use the on-board amplifiers to amplify the
signal, thus preventing the filter from distorting the input signal.
Figure 19 displays the following results of the captured data:
1. Shows the input signal information
2. Displays the fundamental frequency (Fund) and amplitude
in addition to the second (2nd) to fifth (5th) harmonics
3. Displays the performance data: SNR, THD, SINAD, Peak
Spurious Noise, Pk Noise Freq, and Bin Width
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