HI5805_05 Datasheet, PDF (11/12 Pages) Intersil Corporation – 12-Bit, 5MSPS A/D Converter

HI5805
Dynamic Performance Definitions
Fast Fourier Transform (FFT) techniques are used to
evaluate the dynamic performance of the HI5805. A low
distortion sine wave is applied to the input, it is coherently
sampled, and the output is stored in RAM. The data is then
transformed into the frequency domain with an FFT and
analyzed to evaluate the dynamic performance of the A/D.
The sine wave input to the part is -0.5dB down from full scale
for all these tests. SNR and SINAD are quoted in dB. The
distortion numbers are quoted in dBc (decibels with respect
to carrier) and DO NOT include any correction factors for
normalizing to full scale.
Signal-to-Noise Ratio (SNR)
SNR is the measured RMS signal to RMS noise at a
specified input and sampling frequency. The noise is the
RMS sum of all of the spectral components except the
fundamental and the first five harmonics.
Signal-to-Noise + Distortion Ratio (SINAD)
SINAD is the measured RMS signal to RMS sum of all
other spectral components below the Nyquist frequency,
f_S/2, excluding DC.
Effective Number Of Bits (ENOB)
The effective number of bits (ENOB) is calculated from the
SINAD data by:
ENOB = (SINAD + V_CORR-1.76)/6.02,
where: V_CORR = 0.5dB.
V_CORR adjusts the ENOB for the amount the input is below
fullscale.
Total Harmonic Distortion (THD)
THD is the ratio of the RMS sum of the first 5 harmonic
components to the RMS value of the fundamental input
signal.
2nd and 3rd Harmonic Distortion
This is the ratio of the RMS value of the applicable
harmonic component to the RMS value of the fundamental
input signal.
Spurious Free Dynamic Range (SFDR)
SFDR is the ratio of the fundamental RMS amplitude to the
RMS amplitude of the next largest spur or spectral
component in the spectrum below f_S/2.
Intermodulation Distortion (IMD)
Nonlinearities in the signal path will tend to generate
intermodulation products when two tones, f₁ and f₂ , are
present at the inputs. The ratio of the measured signal to
the distortion terms is calculated. The terms included in the
calculation are (f₁ + f₂), (f₁ - f₂), (2f₁), (2f₂), (2f₁ + f₂),
(2f₁ - f₂), (f₁ + 2f₂), (f₁ - 2f₂). The ADC is tested with each
tone 6dB below full scale.
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