Rainbow Electronics MAX1420 User Manual
Page 15
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 endpoints of the transfer function once off-
set and gain errors have been nullified. The static lineari-
ty parameters for the MAX1420 are measured using the
best straight-line fit 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.
Dynamic Parameter Definitions
Aperture Jitter
Figure 10 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
falling edge of the sampling clock and the instant when
an actual sample is taken (Figure 10).
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 ADCs reso-
lution (N-bits):
SNR
MAX
= (6.02 x N + 1.76)
dB
In reality, there are other noise sources besides quanti-
zation noise, e.g., 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 spec-
tral components minus the fundamental, the first four
harmonics, and the DC offset.
Signal-to-Noise Plus Distortion (SINAD)
SINAD is computed by taking the ratio of the RMS sig-
nal to all spectral components minus 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
is computed from:
ENOB
SINADdB
dB
dB
=
−1 76
6 02
.
.
MAX1420
12-Bit, 60Msps, +3.3V, Low-Power ADC
with Internal Reference
______________________________________________________________________________________
15
MAX1420
1nF
1k
Ω
100
Ω
100
Ω
C
IN
22pF
C
IN
22pF
CML
INP
INN
0.1
µF
R
ISO
50
Ω
R
ISO
50
Ω
0.22
µF
V
IN
MAX4108
Figure 9. Single-Ended AC-Coupled Input Signal
HOLD
ANALOG
INPUT
SAMPLED
DATA (T/H)
T/H
t
AD
t
AJ
TRACK
TRACK
CLK
CLK
Figure 10. T/H Aperture Timing