MAX1072 Datasheet, PDF (16/18 Pages) Maxim Integrated Products – 1.8Msps, Single-Supply, Low-Power, True-Differential, 10-Bit ADCs

1.8Msps, Single-Supply, Low-Power,
True-Differential, 10-Bit ADCs
V_L
VDDINT
SUPPLIES
MAX1072 _SCLK
MAX1075
TCLK _{ADSP21_ _ _}
V_DD
GND
V_L
RCLK
CNVST
TFS
RFS
10µF
10µF
DOUT
DR
0.1µF
0.1µF
Figure 19. Interfacing to the ADSP21_ _ _
Signal-to-Noise Ratio
For a waveform perfectly reconstructed from digital sam-
ples, signal-to-noise ratio (SNR) is the ratio of full-scale
analog input (RMS value) to the RMS quantization error
(residual error). The theoretical minimum analog-to-digital
noise is caused by quantization error, and results directly
from the ADC’s resolution (N bits):
SNR = (6.02 x N + 1.76)dB
In reality, there are other noise sources besides quantiza-
tion noise, including thermal noise, reference noise, clock
jitter, etc. Therefore, 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
harmonics, 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:
SINAD(dB) = 20 x log (Signal_RMS / Noise_RMS)
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 quantiza-
tion noise only. With an input range equal to the full-scale
range of the ADC, calculate the ENOB as follows:
ENOB = ^{(SINAD − 1.76)}
6.02
V_DD
GND RGND
V_L
MAX1072
MAX1075
DGND V_L
DIGITAL
CIRCUITRY
Figure 20. Power-Supply Grounding Condition
Total Harmonic Distortion
Total harmonic distortion (THD) is the ratio of the RMS
sum of the first five harmonics of the input signal to the
fundamental itself. This is expressed as:

THD
=
20
x
log


V₂₂
+
V₃₂
+
V₄₂
+
V₅₂


V₁

where V₁ is the fundamental amplitude, and V₂ through
V₅ are the amplitudes of the 2nd- through 5th-order
harmonics.
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.
Full-Power Bandwidth
Full-power bandwidth is the frequency at which the input
signal amplitude attenuates by 3dB for a full-scale input.
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