AD9920ABBCZ datasheet(16/112 Pages) AD

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AD9920A

Rev. B | Page 16 of 112

TERMINOLOGY

Differential Nonlinearity (DNL)

An ideal ADC exhibits code transitions that are exactly 1 LSB

apart. DNL is the deviation from this ideal value. It is often

specified in terms of resolution for which no missing codes are

guaranteed. No missing codes guaranteed to 12-bit resolution

indicates that all 4096 codes, each for its respective input, must

be present over all operating conditions.

Integral Nonlinearity (INL)

INL is defined as the maximum deviation of the actual analog

output from the ideal output, determined by a straight line

drawn from zero scale to full scale.

Peak Nonlinearity

Peak nonlinearity, a full signal chain specification, refers to the

peak deviation of the output of the AD9920A from a true straight

line. The point used as zero scale occurs 0.5 LSB before the first

code transition. Positive full scale is defined as a level 1 LSB and

0.5 LSB beyond the last code transition. The deviation is measured

from the middle of each particular output code to the true straight

line. The error is then expressed as a percentage of the 2 V ADC

full-scale signal. The input signal is always appropriately amplified

to fill the ADC full-scale range.

Power Supply Rejection (PSR)

The PSR is measured with a step change applied to the supply

pins. The PSR specification is calculated from the change in the

data outputs for a given step change in the supply voltage.

Total Output Noise

The rms output noise is measured using histogram techniques.

The standard deviation of the ADC output codes is calculated

in LSB and represents the rms noise level of the total signal

chain at the specified gain setting. The output noise can be

converted to an equivalent voltage using the relationship

1 LSB = (ADC Full Scale/2n Codes)

where n is the bit resolution of the ADC.

For the AD9920A, 1 LSB = 0.244 mV.

AD9920ABBCZ Datasheet(PDF) 16 Page - Analog Devices