Datasheet

DocID025083 Rev 7 69/121
STM32F303x6/x8 Electrical characteristics
101
Note: For information on selecting the crystal, refer to the application note AN2867 “Oscillator
design guide for ST microcontrollers” available at the ST website www.st.com.
Figure 17. Typical application with a 32.768 kHz crystal
Note: An external resistor is not required between OSC32_IN and OSC32_OUT and it is forbidden
to add one.
6.3.8 Internal clock source characteristics
The parameters given in Table 42 are derived from tests performed under ambient
temperature and supply voltage conditions summarized in Table 20.
g
m
Oscillator
transconductance
LSEDRV[1:0]=00
lower-driving capability
5- -
µA/V
LSEDRV[1:0]=10
medium low-driving
capability
8- -
LSEDRV[1:0]=01
medium high-driving
capability
15 - -
LSEDRV[1:0]=11
higher-driving capability
25 - -
t
SU(LSE)
(3)
Startup time V
DD
is stabilized - 2 - s
1. Refer to the note and caution paragraphs below the table, and to the application note AN2867 “Oscillator
design guide for ST microcontrollers”.
2. Guaranteed by design, not tested in production.
3. 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 and it can vary significantly
with the crystal manufacturer.
Table 41. LSE oscillator characteristics (f
LSE
= 32.768 kHz) (continued)
Symbol Parameter Conditions
(1)
Min.
(2)
Typ. Max.
(2)
Unit
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