Datasheet

DocID17050 Rev 9 123/175
STM32F21xxx Electrical characteristics
174
Figure 49. ADC accuracy characteristics
1. Example of an actual transfer curve.
2. Ideal transfer curve.
3. End point correlation line.
4. E
T
= Total Unadjusted Error: maximum deviation between the actual and the ideal transfer curves.
EO = Offset Error: deviation between the first actual transition and the first ideal one.
EG = Gain Error: deviation between the last ideal transition and the last actual one.
ED = Differential Linearity Error: maximum deviation between actual steps and the ideal one.
EL = Integral Linearity Error: maximum deviation between any actual transition and the end point
correlation line.
Figure 50. Typical connection diagram using the ADC
1. Refer to Table 65 for the values of R
AIN
, R
ADC
and C
ADC
.
2. C
parasitic
represents the capacitance of the PCB (dependent on soldering and PCB layout quality) plus the
pad capacitance (roughly 7 pF). A high C
parasitic
value downgrades conversion accuracy. To remedy this,
f
ADC
should be reduced.
ai14395c
E
O
E
G
1L SB
IDEAL
4095
4094
4093
5
4
3
2
1
0
7
6
1 2 3 456 7
4093 4094 4095 4096
(1)
(2)
E
T
E
D
E
L
(3)
V
DDA
V
SSA
V
REF+
4096
(or depending on package)]
V
DDA
4096
[1LSB
IDEAL
=
ai17534
STM32F
V
DD
AINx
I
L
±1 µA
0.6 V
V
T
R
AIN
(1)
C
parasitic
V
AIN
0.6 V
V
T
R
ADC
(1)
C
ADC
(1)
12-bit
converter
Sample and hold ADC
converter