MAX1184 Datasheet, PDF (18/21 Pages) Maxim Integrated Products – Dual 10-Bit, 20Msps, +3V, Low-Power ADC with Internal Reference and Parallel Outputs

Dual 10-Bit, 20Msps, +3V, Low-Power ADC with
Internal Reference and Parallel Outputs
REFP
V_IN
0.1µF
1kΩ _RISO
50Ω
MAX4108
100Ω
INA+
C_IN
1kΩ
22pF
100Ω
COM
REFN
0.1µF
R_ISO
50Ω
INA-
C_IN
22pF
REFP
MAX1184
V_IN
0.1µF
1kΩ RISO
50Ω
MAX4108
100Ω
INB+
C_IN
1kΩ
22pF
100Ω
REFN
0.1µF
R_ISO
50Ω
INB-
C_IN
22pF
Figure 7: Using an Op Amp for Single-Ended, AC-Coupled Input Drive
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_dB x N + 1.76_dB
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.
Effective Number of Bits (ENOB)
ENOB specifies the dynamic performance of an ADC at
a specific input frequency and sampling rate. An ideal
ADC error consists of quantization noise only. ENOB is
computed from:
ENOB = ^{SINADdB − 1.76dB}
6.02_dB
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