WAVEVSN BRD 4.4 National Semiconductor, WAVEVSN BRD 4.4 Datasheet - Page 17

• Manufacturer Part Number: WAVEVSN BRD 4.4
• Description: BOARD INTERFACE DIGITAL HI SPD
• Manufacturer: National Semiconductor
• Series: WaveVisionr

Specifications of WAVEVSN BRD 4.4

• Main Purpose: Interface, Data Capture
• Embedded: Yes, ASIC
• Primary Attributes: ADC & DAC Evaluation
• Secondary Attributes: Graphical User Interface, USB Interface
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Utilized Ic / Part: -

Line Annotation Tool: To draw lines on the plot, select this tool. Drag to draw new lines. To add
arrowheads, or fix the endpoints of the line, double-click it with the arrow tool.
Text Annotation Tool: To draw labels on the plot, select this tool and click at the desired location in the
plot. To edit the justification, location, or text of an annotation, double-click it with the arrow tool.
9.1 The Waveform Plot
The Waveform plot shows you the raw samples collected from the hardware. This plot is mainly used to
verify the integrity of collected data – the waveform is the best view in which to diagnose a distorted
signal, an irregular clock, a low-amplitude signal, and many other common ADC system problems.
The Waveform plot also quickly shows you how much of the ADC’s dynamic range your signal occupies.
9.2 The FFT Plot
The WaveVision4 software automatically computes a Fast Fourier Transform (FFT) of the sample set,
then displays the results in a frequency domain (FFT) plot. This plot is, in many respects, the heart of the
software. The frequency domain plot shows you the frequency content of your input signal, marking the
fundamental frequency, the highest spur, and a selectable number of harmonics. It also labels their order
and frequencies and shows the power in the fundamental and harmonics. Allow your mouse cursor the
hover over a harmonic to get information about it.
The frequency domain plot can be used to diagnose common ADC problems such as input spectral
impurity, clock phase noise, and clock jitter. This plot also shows several statistics on the quality and
purity of the collected samples, such as SNR, SINAD, THD, SFDR, and ENOB. These statistics are to be
interpreted with the following definitions (which are repeated in every National Semiconductor ADC
datasheet):
Signal to Noise Ratio (SNR) is the ratio, expressed in dB, of the RMS value of the input signal to the
RMS value of the sum of all other spectral components below one-half the sampling frequency, not
including harmonics or DC.
Signal to Noise Plus Distortion (S/N+D or SINAD) Is the ratio, expressed in dB, of the RMS value of
the input signal to the RMS value of all of the other spectral components below half the clock frequency,
including harmonics but excluding DC.
Total Harmonic Distortion (THD) is the ratio, expressed in dBc, of the RMS total of the first specified
number of harmonic levels at the output to the level of the fundamental at the output. THD is calculated
as
where f
the first N harmonic frequencies. The default number of harmonics, “N”, in the WaveVision4 software is
initially set to five.
Spurious-Free Dynamic Range (SFDR) is the difference, expressed in dB, between the RMS values of
the input signal and the peak spurious signal, where a spurious signal is any signal present in the output
spectrum that is not present at the input.
THD
=
1
20
is the RMS power of the fundamental (output) frequency and f
log
f
2
2
+
L
f
1
2
+
f
N
2
17
2
through f
N
are the RMS power in