EVAL-AD7686-PMDZ View Datasheet(PDF) - Analog Devices
Part Name
Description
MFG CO.
'EVAL-AD7686-PMDZ' PDF : 31 Pages View PDF
8-/10-Lead PulSAR User Guide
DC TESTING—HISTOGRAM
More commonly, the histogram is used for dc testing where the
user tests the ADC for the code distribution for dc input, computes
the mean and standard deviation, or transition noise, of the
converter, and displays the results. Raw data is captured and
passed to the PC for statistical computations. To perform a
histogram test, select Histogram and click Start Stream. Note
that a histogram test can be performed without an external
source because the evaluation board has a buffered VREF/2
source at the ADC input. To test other dc values, apply a source
to the J6/J10 inputs. It may be required to filter the signal to
make the dc source noise compatible with that of the ADC.
AC TESTING—FFT CAPTURE
This tests the traditional ac characteristics of the converter and
displays an FFT of the result. As in the histogram test, raw data
is captured and passed to the PC where the FFT is performed
displaying signal-to-noise ratio (SNR), signal-to-noise-and-
distortion ratio (SINAD), total harmonic distortion (THD),
UG-340
and spurious-free dynamic range (SFDR). The data can also
be displayed in the time domain. To perform an ac test, apply
a sinusoidal signal to the evaluation board at the SMA inputs,
J6/J10. Low distortion, better than 100 dB, is required to allow
true evaluation of the device. One possibility is to filter the input
signal from the ac source. A band-pass filter can be used, and
its center frequency must match the test frequency of interest.
Furthermore, if using a low frequency band-pass filter when
the full-scale input range is more than a few V p-p, use the on-
board amplifiers to amplify the signal, thus preventing the filter
from distorting the input signal.
Figure 24 displays the histogram of the captured data that includes
the following:
The spectrum information
The fundamental frequency and amplitude in addition to
the second-to-fifth harmonics
The performance data (SNR, dynamic range, THD,
SINAD, and noise performance)
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Figure 24. FFT Tab
Rev. C | Page 13 of 31
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