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STM32F042x4 STM32F042x6
Electrical characteristics
89
Figure 26. ADC accuracy characteristics
Figure 27. Typical connection diagram using the ADC
1. Refer to
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 will downgrade conversion accuracy. To remedy
this, f
ADC
should be reduced.
General PCB design guidelines
Power supply decoupling should be performed as shown in
. The 10 nF capacitor should be ceramic (good quality) and it should be placed as
close as possible to the chip.
2. ADC Accuracy vs. Negative Injection Current: Injecting negative current on any of the standard (non-robust) analog input
pins should be avoided as this significantly reduces the accuracy of the conversion being performed on another analog
input. It is recommended to add a Schottky diode (pin to ground) to standard analog pins which may potentially inject
negative current.
Any positive injection current within the limits specified for I
INJ(PIN)
and
Σ
I
INJ(PIN)
does not affect the ADC
accuracy.
3. Better performance may be achieved in restricted V
DDA
, frequency and temperature ranges.
4. Data based on characterization results, not tested in production.
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