ADC errors AN2834
14/49 DocID15067 Rev 3
Figure 11. Differential linearity error representation
1. The differential linearity error, E
D
, is shown in magenta.
If V
REF+
= 3.3 V, an analog input of 1.9998 V (0x9B1) can provide results varying between
0x9B0 and 0x9B2. Similarly, for an input of 2.0014 V (0x9B3), the results may vary between
0x9B2
and 0x9B4.
As a result, the total voltage variation corresponding to the 0x9B2 step is:
0x9B3 – 0x9B1, that is, 2.0014 V – 1.9998 V = 1.6 mV (1660 µV)
E
D
= 1660 µV – 805.6 µV
E
D
= 854.4 µV
E
D
= (854.4 µV/805.6 µV) LSB
E
D
= 1.06 LSB
Let us assume that no voltage greater than 2.0014 V will result in the 0x9B2 digital code
when the step width is
less than 1 LSB, E
D
is negative.
2.1.4 Integral linearity error
The integral linearity error is the maximum deviation between any actual transition and the
endpoint correlation line. The ILE is denoted by E
L
. It is represented in Figure 12.
The endpoint correlation line can be defined as the line on the A/D transfer curve that
connects
the first actual transition with the last actual transition. E
L
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.
The ILE is also known as the integral non linearity e
rror (INL). The ILE is the integral of the
DLE over the whole range.
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