ADC12DL040

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SNAS250D – FEBRUARY 2005 – REVISED APRIL 2013

Specification Definitions

APERTURE DELAY is the time after the rising edge of the clock to when the input signal is acquired or held for

conversion.

APERTURE JITTER (APERTURE UNCERTAINTY) is the variation in aperture delay from sample to sample.

Aperture jitter manifests itself as noise in the output.

CLOCK DUTY CYCLE is the ratio of the time during one cycle that a repetitive digital waveform is high to the

total time of one period. The specification here refers to the ADC clock input signal.

CONVERSION LATENCY is the number of clock cycles between initiation of conversion and when that data is

presented 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.

CROSSTALK is coupling of energy from one channel into the other channel.

DIFFERENTIAL NON-LINEARITY (DNL) is the measure of the maximum deviation from the ideal step size of 1

LSB.

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

− Negative Full Scale Error

(1)

Gain Error can also be expressed as Positive Gain Error and Negative Gain Error, which are:

PGE = Positive Full Scale Error

− Offset Error

(2)

NGE = Offset Error

− Negative Full Scale Error

(3)

GAIN ERROR MATCHING is the difference in gain errors between the two converters divided by the average

gain of the converters.

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

MISSING CODES are those output codes that will never appear at the ADC outputs. The ADC12DL040 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.

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.

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

rated accuracy.

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