Static parameter definitions, Dynamic parameter definitions – Rainbow Electronics MAX1181 User Manual
Page 16
MAX1181
Dual 10-Bit, 80Msps, +3V, Low-Power ADC with
Internal Reference and Parallel Outputs
16
______________________________________________________________________________________
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
offset and gain errors have been nullified. The static lin-
earity parameters for the MAX1181 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 and a monotonic transfer function.
Dynamic Parameter Definitions
Aperture Jitter
Figure 9 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 9).
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 quantization error only and results directly
from the ADC’s resolution (N-Bits):
SNR
dB[max]
= 6.02
dB
✕
N + 1.76
dB
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 (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:
Total Harmonic Distortion (THD)
THD is typically the ratio of the RMS sum of the first four
harmonics of the input signal to the fundamental itself.
This is expressed as:
THD
V
V
V
V
V
=
×
+
+
+
20
10
2
2
2
2
1
2
3
4
5
log
ENOB
SINAD
dB
dB
dB
=
−1 76
6 02
.
.
MAX1181
T1
N.C.
V
IN
6
1
5
2
4
3
22pF
22pF
0.1
µF
0.1
µF
2.2
µF
25
Ω
25
Ω
MINICIRCUITS
TT1–6
T1
N.C.
V
IN
6
1
5
2
4
3
22pF
22pF
0.1
µF
0.1
µF
2.2
µF
25
Ω
25
Ω
MINICIRCUITS
TT1–6
INA-
INA+
INB-
INB+
COM
Figure 6. Transformer-Coupled Input Drive