Datasheet

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STM32F051x4 STM32F051x6 STM32F051x8 Electrical characteristics
90
Note: For information on selecting the crystal, refer to the application note AN2867 “Oscillator
design guide for ST microcontrollers” available from the ST website www.st.com.
Figure 18. 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 ad
d one.
6.3.8 Internal clock source characteristics
The parameters given in Table 37 are derived from tests performed under ambient
temperature and supply voltage conditions summarized in Table 20: General operating
conditions. The provided curves are characterization results, not tested in production.
g
m
Oscillator
transconductance
LSEDRV[1:0]=00
lower driving capability
5- -
µA/V
LSEDRV[1:0]= 01
medium low driving capability
8- -
LSEDRV[1:0] = 10
medium high driving capability
15 - -
LSEDRV[1:0]=11
higher driving capability
25 - -
t
SU(LSE)
(3)
Startup time V
DDIOx
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 36. LSE oscillator characteristics (f
LSE
= 32.768 kHz)
Symbol Parameter Conditions
(1)
Min
(2)
Typ Max
(2)
Unit
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