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Electrical characteristics
4.
t
SU(LSE)
32.768 kHz oscillation is reached. This value is measured for a standard crystal resonator and it can vary
significantly with the crystal manufacturer.
Note:
For C
and C
L1
15 pF range selected to match the requirements of the crystal or resonator (see
C
and C
L1
capacitance which is the series combination of C
Load capacitance C
C
is the pin capacitance and board or trace PCB-related capacitance. Typically, it is
stray
between 2 pF and 7 pF.
Caution:
To avoid exceeding the maximum value of C
to use a resonator with a load capacitance C
capacitance of 12.5 pF.
Example: if the user chooses a resonator with a load capacitance of C
2 pF, then C
80/134
is the startup time measured from the moment it is enabled (by software) to a stabilized
, it is recommended to use high-quality ceramic capacitors in the 5 pF to
L2
are usually the same size. The crystal manufacturer typically specifies a load
L2,
has the following formula: C
L
= C
= 8 pF.
L1
L2
Figure 17. Typical application with a 32.768 kHz crystal
DocID025433 Rev 8
STM32L151xE STM32L152xE
and C
.
L1
L2
= C
x C
/ (C
L
L1
L2
and C
(15 pF) it is strongly recommended
L1
L2
≤ 7 pF. Never use a resonator with a load
L
Figure
17).
+ C
) + C
where
L1
L2
stray
= 6 pF and C
L
stray
=
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