Datasheet

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A++A

log20=THD

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ADC122S101

SNAS286D –MARCH 2005–REVISED MARCH 2013

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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 that are present at

the output and are not present at the input and result from two sinusoidal frequencies being applied to the

ADC input at the same time. It is defined as the ratio of the power in the intermodulation products to the

total power in one 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 ADC122S101 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.

TOTAL HARMONIC DISTORTION (THD) is the ratio, expressed in dB or dBc, of the rms total of the first five

harmonic components at the output to the rms level of the input signal frequency as seen at the output.

THD is calculated as

(2)

where A

is the RMS power of the input frequency at the output and A

through A

are the

RMS power in the first 5 harmonic frequencies. Accurate THD measurement requires a

spectrally pure sine wave (monotone) at the ADC input.

THROUGHPUT TIME is the minimum time required between the start of two successive conversion. It is the

acquisition time plus the conversion time. In the case of the ADC122S101, this is 16 SCLK periods.

Product Folder Links: ADC122S101