AD9929BBCZ datasheet(7/64 Pages) AD

7 / 64 page

AD9929

Rev. A | Page 7 of 64

TERMINOLOGY

Differential Nonlinearity (DNL)

An ideal ADC exhibits code transitions that are exactly 1 LSB

apart. DNL is the deviation from this ideal value. Thus every

code must have a finite width.“No missing codes guaranteed to

12-bit resolution” indicates that all 4096 codes, respectively,

must be present over all operating conditions.

Peak Nonlinearity

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

peak deviation of the output of the AD9929 from a true straight

line. The point used as zero scale occurs 1/2 LSB before the first

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

1/2 LSB beyond the last code transition. The deviation is mea-

sured 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 appro-

priately gained up to fill the ADC’s full-scale range.

Total Output Noise

The rms output noise is measured using histogram techniques.

The standard deviation of the ADC output codes is calculated

in LSBs, 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) when N is the bit resolution

of the ADC. For the AD9929, 1 LSB is 0.5 mV.

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.

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