MAX1233_05 Datasheet, PDF (43/45 Pages) Maxim Integrated Products – ±15kV ESD-Protected Touch-Screen Controllers Include DAC and Keypad Controller

±15kV ESD-Protected Touch-Screen
Controllers Include DAC and Keypad Controller
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 ideal, theoretical minimum analog-
to-digital noise is caused by quantization error only and
results directly from the ADC’s resolution (N bits):
SNR = (6.02 ✕ N + 1.76) dB
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:
SINAD (dB) = 20 ✕ 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
quantization noise only. With an input range equal to
the full-scale range of the ADC, calculate the effective
number of bits as follows:
ENOB = (SINAD - 1.76) / 6.02
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 × log ^

V₂₂
+
V₃₂
+
V₄₂
+
V₅₂


V₁₂

where V₁ is the fundamental amplitude, and V₂ through
V₅ are the amplitudes of the 2nd- through 5th-order
harmonics, respectively.
Spurious-Free Dynamic Range
Spurious-free dynamic range (SFDR) is the ratio of RMS
amplitude of the fundamental (maximum signal compo-
nent) to the RMS value of the next-largest distortion
component.
Chip Information
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