Information

• Integral non-linearity (INL): This error is defined as the highest-value the (absolute
value of the) running sum of DNL achieves. More simply, this is the worst-case
difference of the actual transition voltage to a given code and its corresponding ideal
transition voltage, for all codes.
• Total unadjusted error (TUE): This error is defined as the difference between the
actual transfer function and the ideal straight-line transfer function and includes all
forms of error.
31.6.2.6 Code jitter, non-monotonicity, and missing codes
Analog-to-digital converters are susceptible to three special forms of error. These are
code jitter, non-monotonicity, and missing codes.
Code jitter is when, at certain points, a given input voltage converts to one of two values
when sampled repeatedly. Ideally, when the input voltage is infinitesimally smaller than
the transition voltage, the converter yields the lower code (and vice-versa). However,
even small amounts of system noise can cause the converter to be indeterminate (between
two codes) for a range of input voltages around the transition voltage.
This error may be reduced by repeatedly sampling the input and averaging the result.
Additionally, the techniques discussed in Noise-induced errors reduces this error.
Non-monotonicity is defined as when, except for code jitter, the converter converts to a
lower code for a higher input voltage. Missing codes are those values never converted for
any input value.
In 8-bit or 10-bit mode, the ADC is guaranteed to be monotonic and have no missing
codes.
Chapter 31 Analog-to-Digital Converter (ADC)
K20 Sub-Family Reference Manual, Rev. 2, Feb 2012
Freescale Semiconductor, Inc. 631