AN1636 Datasheet, PDF (32/42 Pages) STMicroelectronics – UNDERSTANDING AND MINIMISING ADC CONVERSION ERRORS

UNDERSTANDING AND MINIMISING ADC CONVERSION ERRORS
E_D= (5.12mV/4.88mV) LSB
E_D= 1.04 LSB
Here we assume that any voltage greater than 1.010 V will not result in the digital code equal
to CDh.
When the step width is less than 1LSB, DLE will be negative.
5.4 INTEGRAL LINEARITY ERROR
Integral Linearity Error is maximum deviation between any actual transition and the endpoint
correlation line. ILE is represented as E_L.
The endpoint correlation line can be defined as the line on the A/D transfer curve that con-
nects the first actual transition and last actual transition. ILE is the deviation from this line for
each transition. The endpoint correlation line thus corresponds to the actual transfer curve and
has no relation to the ideal transfer curve.
ILE is also known as INL, Integral Non linearity Error. ILE is the integral of DLE over the full
range.
Figure 30. Integral error representation
1023
Digital
output
(Decimal
steps)
1
Endpoint correlation
Line
E_L
E_L = Integral linearity error
Actual
transfer curve
V_SSA
V_IN
Example:
If we get the first transition from 0 to 1 at 10mV ( offset error ) and we get the last transition
(3FE to 3FF) at 4.990V (gain error) then the line on transfer curve connecting the actual digital
code 1 and the actual digital code 3FF will be the endpoint correlation line.
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