MAX1185
Dual 10-Bit, 20Msps, 3V, Low-Power ADC with
Internal Reference and Multiplexed Parallel Outputs
16 ______________________________________________________________________________________
Figure 6. Transformer-Coupled Input Drive
MAX1185
T1
N.C.
V
IN
6
1
5
2
43
22pF
22pF
0.1μF
0.1μF
2.2μF
25Ω
25Ω
MINICIRCUITS
TT1–6
T1
N.C.
V
IN
6
1
5
2
4
3
22pF
22pF
0.1μF
0.1μF
2.2μF
25Ω
25Ω
MINICIRCUITS
TT1–6
INA-
INA+
INB-
INB+
COM
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 MAX1185 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 1 LSB. A DNL
error specification of less than 1 LSB 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 quantiza-
tion error only and results directly from the ADC’s reso-
lution (N-Bits):
SNR
dB[max]
= 6.02 x N + 1.76
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.
MAX1185
Dual 10-Bit, 20Msps, 3V, Low-Power ADC with
Internal Reference and Multiplexed Parallel Outputs
______________________________________________________________________________________ 17______________________________________________________________________________________ 17
MAX1185
0.1μF
1kΩ
1kΩ
100Ω
100Ω
C
IN
22pF
C
IN
22pF
INB+
INB-
COM
INA+
INA-
0.1μF
R
ISO
50Ω
R
ISO
50Ω
REFP
REFN
V
IN
MAX4108
0.1μF
1kΩ
1kΩ
100Ω
100Ω
C
IN
22pF
C
IN
22pF
0.1μF
R
ISO
50Ω
R
ISO
50Ω
REFP
REFN
V
IN
MAX4108
Figure 7. Using an Op Amp for Single-Ended, AC-Coupled Input Drive
MAX1185
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
are backed off by 6.5dB from full scale.
THD
VVVV
V
+++
20
10
2
2
3
2
4
2
5
2
1
log
Dual 10-Bit, 20Msps, 3V, Low-Power ADC with
Internal Reference and Multiplexed Parallel Outputs
18 ______________________________________________________________________________________
Figure 8. Typical QAM Application, Using the MAX1185
HOLD
ANALOG
INPUT
SAMPLED
DATA (T/H)
T/H
t
AD
t
AJ
TRACK TRACK
CLK
Figure 9. T/H Aperture Timing
0°
90°
÷
8
DOWNCONVERTER
MAX2451
INA+
A/B
CHA AND CHB DATA
ALTERNATINGLY
AVAILABLE ON 10-BIT,
MULTIPLEXED
OUTPUT BUS
MAX1185
INA-
INB+
INB-
DSP
POST
PROCESSING

MAX1185ECM+TD

Mfr. #:
Manufacturer:
Maxim Integrated
Description:
Analog to Digital Converters - ADC 10-Bit 2Ch 20Msps High Speed ADC
Lifecycle:
New from this manufacturer.
Delivery:
DHL FedEx Ups TNT EMS
Payment:
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