How is the effective number of bits (ENOB) for an ADC conversion calculated?

For AC applications such as MCP3918, the effective number of bits (ENOB) is calculated from the signal-to-noise and distortion ratio (SINAD), per equation ENOB = (SINAD - 1.76 dB) / 6.02. For DC Applications such as MCP3553, the ENOB is calculated as the ratio of device output noise to full-scale input range, where output noise is the standard deviation (Σ) of the output code distribution.

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