Ai9943
Terminology
Differential Nonlinearity (DNL)
Power Supply Rejection (PSR)
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 10-bit
resolution indicates that all 1024 codes,
respectively, must be present over all
operating conditions.
The PSR is measured with a step change
applied to the supply pins. This represents
a very high frequency disturbance on the
Ai9943’s power supply. The PSR
specification is calculated from the change
in the data outputs for a given step change
in the supply voltage.
Peak Nonlinearity
Internal Delay for SHP/SHD
Peak nonlinearity, a full-signal chain
specification, refers to the peak deviation
of the output of the Ai9943 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 1/2 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.
The internal delay (also called aperture
delay) is the time delay that occurs from
the time a sampling edge is applied to the
Ai9943 until the actual sample of the input
signal is held. Both SHP and SHD sample
the input signal during the transition from
low to high, so the internal delay is
measured from each clock’s rising edge to
the instant the actual internal sample is
taken.
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 example, 1 LSB of the Ai9943 is
1.95 mV
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A1PROS [ A1 PROS CO., LTD. ]
