MAX11661 Datasheet, PDF (26/28 Pages) Maxim Integrated Products – 500ksps, Low-Power, Serial 12-/10-/8-Bit ADCs

500ksps, Low-Power,
Serial 12-/10-/8-Bit ADCs
Definitions
Integral Nonlinearity
Integral nonlinearity (INL) is the deviation of the values
on an actual transfer function from a straight line. For
these devices, the straight line is a line drawn between
the end points of the transfer function after offset and
gain errors are nulled.
Differential Nonlinearity
Differential nonlinearity (DNL) is the difference between
an actual step width and the ideal value of 1 LSB. A DNL
error specification of ±1 LSB or less guarantees no mis-
sing codes and a monotonic transfer function.
Offset Error
The deviation of the first code transition (00 . . . 000) to
(00 . . . 001) from the ideal, that is, AGND + 0.5 LSB.
Gain Error
The deviation of the last code transition (111 . . . 110) to
(111 . . . 111) from the ideal after adjusting for the offset
error, that is, VREF - 1.5 LSB.
Aperture Jitter
Aperture jitter (tAJ) is the sample-to-sample variation in
the time between the samples.
Aperture Delay
Aperture delay (tAD) is the time between the falling edge
of sampling clock and the instant when an actual sample
is taken.
Signal-to-Noise Ratio (SNR)
SNR is a dynamic figure of merit that indicates the con-
verter’s noise performance. For a waveform perfectly
reconstructed from digital samples, the theoretical maxi-
mum SNR is the ratio of the full-scale analog input (RMS
value) to the RMS quantization error (residual error).
The ideal, theoretical minimum analog-to-digital noise
is caused by quantization error only and results directly
from the ADC’s resolution (N bits):
SNR (dB) (MAX) = (6.02 x N + 1.76) (dB)
In reality, there are other noise sources such as thermal
noise, reference noise, and clock jitter that also degrade
SNR. SNR is computed by taking the ratio of the RMS
signal to the RMS noise. RMS noise includes all spectral
components to the Nyquist frequency excluding the
fundamental, the first five harmonics, and the DC offset.
Signal-to-Noise Ratio and Distortion
(SINAD)
SINAD is a dynamic figure of merit that indicates the
converter’s noise and distortion performance. SINAD
is computed by taking the ratio of the RMS signal to
the RMS noise plus distortion. RMS noise plus distor-
tion includes all spectral components to the Nyquist
frequency excluding the fundamental and the DC offset:
.
SINAD(dB)
=
20
×
log

^(NOISE
SIGNAL _RMS
+ DISTORTION)
RMS



Total Harmonic Distortion
Total harmonic distortion (THD) is the ratio of the RMS
sum of the first five harmonics of the input signal to the
fundamental itself. This is expressed as:

THD = 20 × log^{}
V₂₂
+
V₃₂
+
V₄₂
+
V₅₂


V₁

where V1 is the fundamental amplitude and V2–V5 are
the amplitudes of the 2nd- through 5th-order harmonics.
Spurious-Free Dynamic Range (SFDR)
SFDR is a dynamic figure of merit that indicates the low-
est usable input signal amplitude. SFDR is the ratio of
the RMS amplitude of the fundamental (maximum signal
component) to the RMS value of the next largest spuri-
ous component, excluding DC offset. SFDR is specified
in decibels with respect to the carrier (dBc).
Full-Power Bandwidth
Full-power bandwidth is the frequency at which the input
signal amplitude attenuates by 3dB for a full-scale input.
Full-Linear Bandwidth
Full-linear bandwidth is the frequency at which the
signal-to-noise ratio and distortion (SINAD) is equal to a
specified value.
Intermodulation Distortion
Any device with nonlinearities creates distortion prod-
ucts when two sine waves at two different frequencies
(f1 and f2) are applied into the device. Intermodulation
distortion (IMD) is the total power of the IM2 to IM5 inter-
modulation products to the Nyquist frequency relative to
the total input power of the two input tones, f1 and f2. The
individual input tone levels are at -6dBFS.
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