MAX1184 Maxim Integrated Products, MAX1184 Datasheet - Page 18

• Manufacturer Part Number: MAX1184
• Description: Low-Power ADC
• Manufacturer: Maxim Integrated Products

Dual 10-Bit, 20Msps, +3V, Low-Power ADC with
Internal Reference and Parallel Outputs
Figure 7: Using an Op Amp for Single-Ended, AC-Coupled Input Drive
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):
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.
18
______________________________________________________________________________________
SNR
dB[max]
Signal-to-Noise Ratio (SNR)
V
V
IN
IN
= 6.02
dB
MAX4108
MAX4108
x N + 1.76
100Ω
100Ω
100Ω
100Ω
dB
0.1µF
0.1µF
REFN
REFN
REFP
REFP
1kΩ
1kΩ
1kΩ
1kΩ
R
50Ω
R
50Ω
ISO
ISO
0.1µF
0.1µF
SINAD is computed by taking the ratio of the RMS sig-
nal to all spectral components minus the fundamental
and the DC offset.
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:
Signal-to-Noise Plus Distortion (SINAD)
C
22pF
C
22pF
IN
IN
22pF
22pF
R
50Ω
C
50Ω
R
C
ISO
IN
ISO
IN
ENOB
Effective Number of Bits (ENOB)
INA+
COM
INA-
INB+
INB-
=
MAX1184
SINAD
6 02
dB
.
−
dB
1 76
.
dB