ADC12DL080

SNAS345A – FEBRUARY 2006 – REVISED APRIL 2013

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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 intermodulation products to the total power in the original frequencies. IMD is usually expressed in dBFS.

LSB (LEAST SIGNIFICANT BIT) is the bit that has the smallest value or weight of all bits. This value is VFS/2

n,

where “VFS” is the full scale input voltage and “n” is the ADC resolution in bits.

MISSING CODES are those output codes that will never appear at the ADC outputs. The ADC12DL080 is

ensured not to have any missing codes.

MSB (MOST SIGNIFICANT BIT) is the bit that has the largest value or weight. Its value is one half of full scale.

NEGATIVE FULL SCALE ERROR is the difference between the actual first code transition and its ideal value of

½ LSB above negative full scale.

OFFSET ERROR is the difference between the two input voltages [(VIN+) – (VIN−)] required to cause a transition

from code 2047 to 2048.

OUTPUT DELAY is the time delay after the rising edge of the clock before the data update is presented at the

output pins.

OVER RANGE RECOVERY TIME is the time required after VIN goes from a specified voltage out of the normal

input range to a specified voltage within the normal input range and the converter makes a conversion with its

rated accuracy.

PIPELINE DELAY (LATENCY) See CONVERSION LATENCY.

POSITIVE FULL SCALE ERROR is the difference between the actual last code transition and its ideal value of

1½ LSB below positive full scale.

POWER SUPPLY REJECTION RATIO (PSRR) is a measure of how well the ADC rejects a change in the power

supply voltage. For the ADC12DL080, PSRR1 is the ratio of the change in Full-Scale Error that results from a

change in the d.c. power supply voltage, expressed in dB. PSRR2 is a measure of how well an a.c. signal riding

upon the power supply is rejected at the output.

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, of the rms total of the first nine harmonic

levels at the output to the level of the fundamental at the output. THD is calculated as

(2)

where f1 is the RMS power of the fundamental (output) frequency and f2 through f10 are the RMS power of the

first 9 harmonic frequencies in the output spectrum.

SECOND HARMONIC DISTORTION (2ND HARM) is the difference expressed in dB, between the RMS power in

the input frequency at the output and the power in its 2nd harmonic level at the output.

THIRD HARMONIC DISTORTION (3RD HARM) is the difference, expressed in dB, between the RMS power in

the input frequency at the output and the power in its 3rd harmonic level at the output.

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