Rainbow Electronics MAX1444 User Manual
Page 15
MAX1444
10-Bit, 40Msps, +3.0V, Low-Power
ADC with Internal Reference
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15
Static Parameter Definitions
Integral Nonlinearity
Integral nonlinearity (INL) 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
MAX1444’s static linearity parameters are measured
using the best straight-line fit method.
Differential Nonlinearity
Differential nonlinearity (DNL) 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
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 A/D 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.
MAX1444
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
IN-
IN+
COM
Figure 8. Using a Transformer for AC Coupling
MAX1444
0.1
µF
1k
1k
100
Ω
100
Ω
C
IN
COM
C
IN
IN+
IN-
0.1
µF
R
ISO
R
ISO
REFP
REFN
R
ISO
= 50
Ω
C
IN
= 22pF
V
IN
MAX4108
Figure 9. Single-Ended AC-Coupled Input