Datasheet

MAX1184
Dual 10-Bit, 20Msps, 3V, Low-Power ADC with
Internal Reference and Parallel Outputs
18 ______________________________________________________________________________________
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 quantiza-
tion 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 x N + 1.76
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 five
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.
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:
where V
1
is the fundamental amplitude, and V
2
through
V
5
are the amplitudes of the 2nd- through 5th-order
harmonics.
Spurious-Free Dynamic Range (SFDR)
SFDR is the ratio expressed in decibels of the RMS
amplitude of the fundamental (maximum signal compo-
nent) to the RMS value of the next largest spurious
component, excluding DC offset.
Intermodulation Distortion (IMD)
The two-tone IMD is the ratio expressed in decibels of
either input tone to the worst 3rd-order (or higher) inter-
modulation products. The individual input tone levels
backed off by 6.5dB from full scale.
THD
VVVV
V
=×
+++
⎛
⎝
⎜
⎜
⎞
⎠
⎟
⎟
20
10
2
2
3
2
4
2
5
2
1
log
HOLD
ANALOG
INPUT
SAMPLED
DATA (T/H)
T/H
t
AD
t
AJ
TRACK TRACK
CLK
Figure 9. T/H Aperture Timing
PART
RESOLUTION
(BITS)
SPEED GRADE
(Msps)
OUTPUT
BUS
MAX1190 10 120 Full-Duplex
MAX1180 10 105 Full-Duplex
MAX1181 10 80 Full-Duplex
MAX1182 10 65 Full-Duplex
MAX1183 10 40 Full-Duplex
MAX1186 10 40 Half-Duplex
MAX1184 10 20 Full-Duplex
MAX1185 10 20 Half-Duplex
MAX1198 8 100 Full-Duplex
MAX1197 8 60 Full-Duplex
MAX1196 8 40 Half-Duplex
MAX1195 8 40 Full-Duplex
Table 2. Pin-Compatible Versions