Optimizing Evaluation Results
9
SLAU712 – February 2017
Copyright © 2017, Texas Instruments Incorporated
ADC08L060 Evaluation Module
3
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
for more information
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 3. HSDC Pro Settings to Optimize 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 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.
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 and 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
.
