W

THD = 20 log10

Af1

2



Af2

2

+

+ Af6

2

ADC101S021

www.ti.com

SNAS307G – JULY 2005 – REVISED JANUARY 2014

MISSING CODES are those output codes that will never appear at the ADC outputs. The ADC101S021 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 to the rms

value of the sum of all other spectral components below one-half the sampling frequency, not including

harmonics or d.c.

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

where

•

Af1 is the RMS power of the input frequency at the output

•

Af2 through Af6 are the RMS power in the first 5 harmonic frequencies

(1)

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

acquisition time plus the conversion time.

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