AD9949 datasheet(8/36 Pages) AD

8 / 36 page

AD9949

Rev. B | Page 8 of 36

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.

Integral Nonlinearity (INL)

INL is the deviation of each individual code measured from a

true straight line from zero to full scale. 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.

Peak Nonlinearity

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

peak deviation of the output of the AD9949 from a 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

straight line reference. The error is then expressed as a

percentage of the 2 V ADC full-scale signal. The input signal is

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

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

verted 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 AD9949,

1 LSB is approximately 0.488 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.

AD9949 Datasheet(PDF) 8 Page - Analog Devices