Datasheet

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
.
.
MAX1421
12-Bit, 40Msps, 3.3V, Low-Power ADC
with Internal Reference
______________________________________________________________________________________ 15
MAX1421
T1
N.C.
V
IN
6
1
5
2
43
22pF
22pF
1nF
0.1µF
0.22µF
25Ω
25Ω
MINICIRCUITS
T1–1T–KK81
INN
INP
CML
44pF
*
*
*
*REPLACE BOTH 22pF CAPS WITH 44pF BETWEEN
INP AND INN TO IMPROVE DYNAMIC PERFORMANCE.
Figure 8. Using a Transformer for AC-Coupling
MAX1421
1nF
1kΩ100Ω
100Ω
C
IN
22pF
CML
C
IN
22pF
INP
INN
0.1µF
R
ISO
50Ω
R
ISO
50Ω
0.22µF
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. Track-and-Hold Aperture Timing