AD9942BBCZ datasheet(11/36 Pages) AD

11 / 36 page

AD9942

Rev. A | Page 11 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. Therefore,

every code must have a finite width. No missing codes

guaranteed to 12-bit resolution indicates that all 4096 codes

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 AD9942 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 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

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 AD9942,

1 LSB is approximately 122.0 μV.

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.

Matching Error

The matching error refers to the Channel A to Channel B

mismatch after post-ADC correction calibration has been

applied to remove gain error between Channel A and

Channel B.

Crosstalk

The crosstalk is measured while applying a full-scale step to

one channel and measuring the interference on the opposite

channel.

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Crosstalk

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