Owner's manual
MAX1449
10-Bit, 105Msps, Single +3.3V, Low-Power
ADC with Internal Reference
______________________________________________________________________________________ 15
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 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 sam-
ples, 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 ana-
log-to-digital noise is caused by quantization error only
and results directly from the ADC’s resolution (N Bits):
SNR
(MAX)
= (6.02 x 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:
ENOB
SINAD
.
.
=
−
()
176
602
MAX1449
T1
N.C.
V
IN
6
1
5
2
43
22pF
22pF
0.1µF
0.1µF
2.2µF
25Ω
25Ω
MINICIRCUITS
TT1–6
IN-
IN+
COM
Figure 8. Using a Transformer for AC Coupling
MAX1449
0.1µF
1k
1k
100Ω
100Ω
C
IN
COM
C
IN
IN+
IN-
0.1µF
R
ISO
R
ISO
REFP
REFN
R
ISO
= 50Ω
C
IN
= 22pF
V
IN
MAX4108
Figure 9. Single-Ended AC-Coupled Input