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STM32L162VC, STM32L162RC
104
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
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 the user chooses a resonator with a load capacitance of C
L
= 6 pF and C
stray
=
2 pF, then C
L1
= C
L2
= 8 pF.
Figure 15. Typical application with a 32.768 kHz crystal
4. t
SU(LSE)
is the startup time measured from the moment it is enabled (by software) to a stabilized
32.768 kHz oscillation is reached. This value is measured for a standard crystal resonator and it can vary
significantly with the crystal manufacturer.
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