MAX1319/MAX1323/MAX1327
526ksps, Single-Channel,
14-Bit, Parallel-Interface ADCs
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Bipolar Offset Error
For the bipolar MAX1323/MAX1327, the ideal zero-point
transition from 0x3FFF to 0x0000 occurs at MSV, which
is usually connected to ground (see Figures 6 and 7).
The bipolar offset error is the amount of deviation
between the measured zero-point transition and the
ideal zero-point transition.
Gain Error
The ideal full-scale transition from 0x1FFE to 0x1FFF
occurs at 1 LSB below full scale (see the Transfer
Functions section). The gain error is the amount of devi-
ation between the measured full-scale transition point
and the ideal full-scale transition point, once offset error
has been nullified.
Signal-to-Noise Ratio
For a waveform perfectly reconstructed from digital
samples, signal-to-noise ratio (SNR) is the ratio of the
full-scale analog input (RMS value) to the RMS quanti-
zation error (residual error). The ideal, theoretical mini-
mum analog-to-digital noise is caused by quantization
noise error only and results directly from the ADC’s res-
olution (N bits):
where N = 14 bits.
In reality, there are other noise sources besides quanti-
zation noise; thermal noise, reference noise, clock jitter,
etc. SNR is computed by taking the ratio of the RMS
signal to the RMS noise, which includes all spectral
components minus the fundamental, the first five har-
monics, and the DC offset.
Signal-to-Noise Plus Distortion
Signal-to-noise plus distortion (SINAD) is the ratio of the
fundamental input frequency’s RMS amplitude to the
RMS equivalent of all the other ADC output signals.
Effective Number of Bits
Effective number of bits (ENOB) indicates the global
accuracy of an ADC at a specific input frequency and
sampling rate. An ideal ADC’s error consists of quanti-
zation noise only. With an input range equal to the full-
scale range of the ADC, calculate the ENOB as follows:
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:
where V
1
is the fundamental amplitude and V
2
through
V
5
are the 2nd- through 5th-order harmonics.
Spurious-Free Dynamic Range
Spurious-free dynamic range (SFDR) is the ratio of the
RMS amplitude of the fundamental (maximum signal
component) to the RMS value of the next largest fre-
quency component.
Aperature Delay
Aperture delay (t
AD
) is the time delay from the sampling
clock edge to the instant when an actual sample is taken.
Aperture Jitter
Aperture Jitter (t
AJ
) is the sample-to-sample variation in
aperture delay.
Small-Signal Bandwidth
A small -20dBFS analog input signal is applied to an
ADC in a manner that ensures that the signal’s slew
rate does not limit the ADC’s performance. The input
frequency is then swept up to the point where the
amplitude of the digitized conversion result has
decreased by -3dB.
Full-Power Bandwidth
A large -0.5dBFS analog input signal is applied to an
ADC, and the input frequency is swept up to the point
where the amplitude of the digitized conversion result
has decreased by -3dB. This point is defined as full-
power input bandwidth frequency.
