Optimizing Evaluation Results; Clocking Optimization; Coherent Input Source; Hsdc Pro Settings - Texas Instruments ADC08L060EVM User Manual

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Optimizing Evaluation Results

This section assists the user in optimizing the performance during evaluation of the product.
3.1

Clocking Optimization

The sampling clock provided to the ADC needs to have very low phase noise to achieve optimal results.
The default EVM configuration uses a crystal oscillator to generate the sampling clock. Another option to
improve the clock noise performance is bypassing the onboard clock in favor of an external clock. The
clock must have very low noise and must use an external narrow pass-band filter to achieve optimal noise
performance. The clock amplitude must be within the data sheet limits. See
regarding this setup.
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 settings that can help improve the performance measurements. These are
highlighted in Table
HSDC Pro Feature
Analysis Window (Samples)
Data Windowing Function
Test Options → Notch
Frequency Bins
Test Options → Bandwidth
Integration Markers
Data Capture Options →
Capture Options
SLAU712 – February 2017
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Table 3. HSDC Pro Settings to Optimize Results
Description
Selects the number of samples to include in the selected test analysis. Collect more data to
improve frequency resolution of Fast-Fourier Transform (FFT) analysis. If more than 65,536
samples are required, increase the setting in the Data Capture Options to match this value.
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.
Select bins to be removed from the spectrum and back-filled with the average noise level. May
also customize which Harmonics and Spurs are considered in SNR and THD calculations and
select the method for calculating spur power.
Enable markers to narrow the Single-Tone FFT test analysis to a specific bandwidth.
Configure the number of contiguous samples per capture (capture depth). May also enable
Continuous Capture and FFT Averaging.
Copyright © 2017, Texas Instruments Incorporated
Optimizing Evaluation Results
Section 4 for more information
ADC08L060 Evaluation Module
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