DocID15067 Rev 3 23/49
AN2834 How to get the best ADC accuracy
48
To filter high-frequency noise, a ferrite inductance in series with the power supply can be
used. This solution leads to very low (negligible) DC loss unless the current is high because
the series resistance of the wire is very low. At high frequencies, however, the impedance is
high.
STM32 microcontroller side
In most STM32 microcontrollers, the V
DD
and V
SS
pins are placed close to each other. So
are the V
REF+
and V
SSA
pins. A capacitor can therefore be connected very close to the
microcontroller with very short leads. For multiple V
DD
and V
SS
pins, use separate
decoupling capacitors.
The V
DDA
pin must be connected to two external decoupling capacitors (10 nF Ceramic +
1 µF Tantalum or Ceramic). Refer to F
igure 20 and Figure 21 for decoupling examples.
For STM32 microcontrollers delivered in 100/144-pin packages, it is possible to improve the
ac
curacy on low-voltage inputs by connecting a separate external ADC reference voltage
input on V
REF+
(refer to Section 3.2.5). The voltage on V
REF+
may range from 2.4 V to
V
DDA
. If a separate, external reference voltage is applied on V
REF+
, two 10 nF and 1 µF
capacitors must be connected on this pin. In all cases, V
REF+
must be kept between 2.4 V
and V
DDA
.
Figure 20. Power supply and reference decoupling for 100- and 144-pin packages
Figure 21. Power supply decoupling for 36-, 48- and 64-pin packages
To Next Page
Loading...
Need help?
General
