Datasheet

STM32L100C6, STM32L100R8/RB Electrical characteristics
DocID024295 Rev 1 63/102
Note: For C
L1
and C
L2
, it is recommended to use high-quality ceramic capacitors in the 5 pF to
15 pF range selected to match the requirements of the crystal or resonator (see Figure 13).
C
L1
and C
L2,
are usually the same size. The crystal manufacturer typically specifies a load
capacitance which is the series combination of C
L1
and C
L2
.
Load capacitance C
L
has the following formula: C
L
= C
L1
x C
L2
/ (C
L1
+ C
L2
) + C
stray
where
C
stray
is the pin capacitance and board or trace PCB-related capacitance. Typically, it is
between 2 pF and 7 pF.
Caution: To avoid exceeding the maximum value of C
L1
and C
L2
(15 pF) it is strongly recommended
to use a resonator with a load capacitance C
L
≤ 7 pF. Never use a resonator with a load
capacitance of 12.5 pF.
Example: if you choose a resonator with a load capacitance of C
L
= 6 pF and C
stray
= 2 pF,
then C
L1
= C
L2
= 8 pF.
Figure 13. Typical application with a 32.768 kHz crystal
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