Datasheet

ADC122S051

SNAS257E –NOVEMBER 2004–REVISED MARCH 2013

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EFFECTIVE NUMBER OF BITS (ENOB, or EFFECTIVE BITS) is another method of specifying Signal-to-Noise

and Distortion or SINAD. ENOB is defined as (SINAD − 1.76) / 6.02 and says that the converter is equivalent to

a perfect ADC of this (ENOB) number of bits.

FULL POWER BANDWIDTH is a measure of the frequency at which the reconstructed output fundamental

drops 3 dB below its low frequency value for a full scale input.

FULL SCALE ERROR (FSE) is a measure of how far the last code transition is from the ideal 1½ LSB below

REF

and is defined as:

FSE

= V

max

+ 1.5 LSB – V

REF

(1)

where V

max

is the voltage at which the transition to the maximum code occurs. FSE can be expressed in Volts,

LSB or percent of full scale range.

GAIN ERROR is the deviation of the last code transition (111...110) to (111...111) from the ideal (V

REF

− 1.5

LSB), after adjusting for offset error.

INTEGRAL NON-LINEARITY (INL) is a measure of the deviation of each individual code from a line drawn from

negative full scale (½ LSB below the first code transition) through positive full scale (½ LSB above the last code

transition). The deviation of any given code from this straight line is measured from the center of that code value.

INTERMODULATION DISTORTION (IMD) is the creation of additional spectral components as a result of two

sinusoidal frequencies being applied to the ADC input at the same time. It is defined as the ratio of the power in

the second and third order intermodulation products to the sum of the power in both of the original frequencies.

IMD is usually expressed in dB.

MISSING CODES are those output codes that will never appear at the ADC outputs. These codes cannot be

reached with any input value. The ADC122S051/ADC122S051Q is ensured not to have any missing codes.

OFFSET ERROR is the deviation of the first code transition (000...000) to (000...001) from the ideal (i.e. GND +

0.5 LSB).

SIGNAL TO NOISE RATIO (SNR) is the ratio, expressed in dB, of the rms value of the input signal at the

converter output to the rms value of the sum of all other spectral components below one-half the sampling

frequency, not including d.c. or harmonics included in the THD specification.

SIGNAL TO NOISE PLUS DISTORTION (S/N+D or SINAD) Is the ratio, expressed in dB, of the rms value of the

input signal to the rms value of all of the other spectral components below half the clock frequency, including

harmonics but excluding d.c.

SPURIOUS FREE DYNAMIC RANGE (SFDR) is the difference, expressed in dB, between the desired signal

amplitude to the amplitude of the peak spurious spectral component, where a spurious spectral component is

any signal present in the output spectrum that is not present at the input and may or may not be a harmonic.

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