Texas Instruments ADC31JB68, User Manual, Page: 10 / 20

Optimizing Evaluation Results
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10 SLAU630A – August 2015 – Revised August 2016
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ADC31JB68 Evaluation Module
3 Optimizing Evaluation Results
This section describes how to optimize the performance during evaluation of the product.
3.1 Clocking Optimization
The sampling clock provided to the ADC must have very low noise to achieve optimal results. The
ADC31JB68EVM is configured by default to require a device clock from an external signal source via the
CLK SMA connector to allow for the best possible measured performance.
3.2 Coherent Input Source
A Rectangular window function can be applied to the captured data when the sample rate and the input
frequency are set precisely to capture an integer number of cycles of the input frequency (sometimes
called coherent frequency). This may yield better SNR results. The clock and analog inputs must be
frequency locked (such as through 10-MHz references) in order to achieve coherency.
3.3 HSDC Pro Settings
HSDC Pro has some options that can help improve the performance measurements. These are
highlighted in
Table 3 .
Table 3. HSDC Pro Options for Optimal Analysis Results
HSDC Pro Feature Description
Analysis Window (samples) Selects the number of samples to include in the selected test analysis. Collect more
data to improve frequency resolution of FFT analysis.
Data Windowing Function Select the desired windowing function applied to the data for FFT analysis. Select
Blackman when sampling a non-coherent input signal or Rectangle when sampling a
coherent input signal.
Test Options → Notch Frequency Bins Select bins to be removed from the spectrum and back-filled with the average noise
level. May also customize which Harmonics/Spurs are considered in SNR and THD
calculations and select the method for calculating spur power.
Test Options → Bandwidth Integration
Markers
Enable markers to narrow the Single-Tone FFT test analysis to a specific bandwidth
Data Capture Options → Capture Options Configure the number of contiguous samples per capture (capture depth). May also
enable
Continuous Capture and FFT Averaging .