Instruction Manual

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Specification Definitions

APERTURE DELAY is the time after the rising edge of the

clock to when the input signal is acquired or held for conver-

sion.

APERTURE JITTER (APERTURE UNCERTAINTY) is the

variation in aperture delay from sample to sample. Aperture

jitter manifests itself as noise in the output.

COMMON MODE VOLTAGE (V

) is the d.c. potential

present at both signal inputs to the ADC.

CONVERSION LATENCY See PIPELINE DELAY.

DIFFERENTIAL NON-LINEARITY (DNL) is the measure of

the maximum deviation from the ideal step size of 1 LSB.

DUTY CYCLE is the ratio of the time that a repetitive digital

waveform is high to the total time of one period. The speci-

fication here refers to the ADC clock input signal.

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.

GAIN ERROR is the deviation from the ideal slope of the

transfer function. It can be calculated as:

Gain Error = Positive Full Scale Error − Offset Error

INTEGRAL NON LINEARITY (INL) is a measure of the

deviation of each individual code from a best fit straight line.

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 power in one of the

original frequencies. IMD is usually expressed in dBFS.

MISSING CODES are those output codes that will never

appear at the ADC outputs. The ADC12L080 is guaranteed

not to have any missing codes.

NEGATIVE FULL SCALE ERROR is the difference between

the input voltage (V

+−V

−) just causing a transition from

negative full scale to the first code and its ideal value of 0/5

LSB.

OFFSET ERROR is the input voltage that will cause a tran-

sition from a code of 01 1111 1111 to a code of 10 0000 0000/

OUTPUT DELAY is the time delay after the rising edge of

the clock before the data update is presented at the output

pins.

PIPELINE DELAY (LATENCY) is the number of clock cycles

between initiation of conversion and when that data is pre-

sented to the output driver stage. Data for any given sample

is available at the output pins the Pipeline Delay plus the

Output Delay after the sample is taken. New data is available

at every clock cycle, but the data lags the conversion by the

pipeline delay.

POSITIVE FULL SCALE ERROR is the difference between

the actual last code transition and its ideal value of 1

⁄

LSB

below positive full scale.

POWER SUPPLY REJECTION RATIO (PSRR) is a mea-

sure of how well the ADC rejects a change in the power

supply voltage. PSRR1 is the ratio of the change in Full-

Scale Gain 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 compo-

nents below half the clock frequency, including harmonics

but excluding d.c.

SPURIOUS FREE DYNAMIC RANGE (SFDR) is the differ-

ence, expressed in dB, between the rms values of the input

signal and the peak spurious signal, where a spurious signal

is any signal present in the output spectrum that is not

present at the input.

TOTAL HARMONIC DISTORTION (THD) is the ratio, ex-

pressed in dBc, 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

where A

is the RMS power of the fundamental (output)

frequency and A

through A

f10

are the RMS power in the first

9 harmonic frequencies.

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.

ADC12L080