
MAX11612–MAX11617
Low-Power, 4-/8-/12-Channel, I2C,
12-Bit ADCs in Ultra-Small Packages
21
Maxim Integrated
Signal-to-Noise Ratio
For a waveform perfectly reconstructed from digital sam-
ples, 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 ana-
log-to-digital noise is caused by quantization error only
and results directly from the ADC’s resolution (N Bits):
SNRMAX[dB] = 6.02dB N + 1.76dB
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
Signal-to-noise plus distortion (SINAD) is the ratio of the
fundamental input frequency’s RMS amplitude to the
RMS equivalent of all other ADC output signals.
Effective Number of Bits
Effective number of bits (ENOB) indicates the global
accuracy of an ADC at a specific input frequency and
sampling rate. An ideal ADC’s error consists of quanti-
zation noise only. With an input range equal to the
ADC’s full-scale range, calculate the ENOB as follows:
ENOB = (SINAD - 1.76)/6.02
Total Harmonic Distortion
Total harmonic distortion (THD) is the ratio of the RMS
sum of the input signal’s first five harmonics to the fun-
damental itself. This is expressed as:
where V1 is the fundamental amplitude, and V2 through
V5 are the amplitudes of the 2nd- through 5th-order har-
monics.
Spurious-Free Dynamic Range
Spurious-free dynamic range (SFDR) is the ratio of the
RMS amplitude of the fundamental (maximum signal
component) to the RMS value of the next largest distor-
tion component.
THD
VVV
V
log
=×
++
+
20
2
3
2
4
2
5
2
1
SINAD dB
SignalRMS
NoiseRMS THDRMS
(
)
log
=×
+
20
Chip Information
PROCESS: BiCMOS
MAX11612–MAX11617
PART
INPUT
CHANNELS
INTERNAL
REFERENCE
(V)
SUPPLY
VOLTAGE
(V)
INL
(LSB)
MAX11612
4
4.096
4.5 to 5.5
±1
MAX11613
4
2.048
2.7 to 3.6
±1
MAX11614
8
4.096
4.5 to 5.5
±1
MAX11615
8
2.048
2.7 to 3.6
±1
MAX11616
12
4.096
4.5 to 5.5
±1
MAX11617
12
2.048
2.7 to 3.6
±1
Selector Guide