MAX1192 Datasheet, PDF (25/28 Pages) Maxim Integrated Products – Ultra-Low-Power, 22Msps, Dual 8-Bit ADC

Ultra-Low-Power, 22Msps, Dual 8-Bit ADC
CLK
ANALOG
INPUT
t_AD
t_AJ
SAMPLED
DATA (T/H)
T/H ^TRACK
HOLD
TRACK
Figure 13. T/H Aperture Timing
Static Parameter Definitions
Integral Nonlinearity (INL)
Integral nonlinearity is the deviation of the values on an
actual transfer function from a straight line. This straight
line can be either a best-straight-line fit or a line drawn
between the end points of the transfer function, once
offset and gain errors have been nullified. The static lin-
earity parameters for the MAX1192 are measured using
the end-point method.
Differential Nonlinearity (DNL)
Differential nonlinearity is the difference between an
actual step width and the ideal value of 1LSB. A DNL
error specification of less than 1LSB guarantees no
missing codes and a monotonic transfer function.
Offset Error
Ideally, the midscale MAX1192 transition occurs at 0.5
LSB above midscale. The offset error is the amount of
deviation between the measured transition point and
the ideal transition point.
Gain Error
Ideally, the full-scale MAX1192 transition occurs at 1.5
LSB below full-scale. The gain error is the amount of
deviation between the measured transition point and
the ideal transition point with the offset error removed.
Dynamic Parameter Definitions
Aperture Jitter
Figure 13 depicts the aperture jitter (t_AJ), which is the
sample-to-sample variation in the aperture delay.
Aperture Delay
Aperture delay (t_AD) is the time defined between the
rising edge of the sampling clock and the instant when
an actual sample is taken (Figure 13).
Signal-to-Noise Ratio (SNR)
For a waveform perfectly reconstructed from digital
samples, the theoretical maximum 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 quantiza-
tion error only and results directly from the ADC’s reso-
lution (N bits):
SNR_dB[max] = 6.02 × N + 1.76
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. RMS noise includes all spec-
tral components to the Nyquist frequency excluding the
fundamental, the first five harmonics, and the DC offset.
Signal-to-Noise Plus Distortion (SINAD)
SINAD is computed by taking the ratio of the RMS sig-
nal to the RMS noise. RMS noise includes all spectral
components to the Nyquist frequency excluding the
the fundamental and the DC offset.
Effective Number of Bits (ENOB)
ENOB specifies the dynamic performance of an ADC at
a specific input frequency and sampling rate. An ideal
ADC’s error consists of quantization noise only. ENOB
for a full-scale sinusoidal input waveform is computed
from:
ENOB = ^{SINAD - 1.76}
6.02
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