Datasheet

Electrical characteristics STM32F100xC, STM32F100xD, STM32F100xE
52/105 DocID15081 Rev 8
Figure 14. Typical application with a 32.768 kHz crystal
5.3.7 Internal clock source characteristics
The parameters given in Table 24 are derived from tests performed under the ambient
temperature and V
DD
supply voltage conditions summarized in Table 9.
Table 23. LSE oscillator characteristics (f
LSE
= 32.768 kHz)
(1)
Symbol Parameter Conditions Min Typ Max Unit
R
F
Feedback resistor 5 MΩ
C
L1
C
L2
(2)
Recommended load capacitance
versus equivalent serial
resistance of the crystal (R
S
)
(3)
R
S
= 30 KΩ 15 pF
I
2
LSE driving current
V
DD
= 3.3 V
V
IN
= V
SS
1.4 µA
g
m
Oscillator transconductance 5 µA/V
t
SU(LSE)
(4)
Startup time
V
DD
is
stabilized
T
A
= 50 °C 1.5
s
T
A
= 25 °C 2.5
T
A
= 10 °C 4
T
A
= 0 °C 6
T
A
= -10 °C 10
T
A
= -20 °C 17
T
A
= -30 °C 32
T
A
= -40 °C 60
1. Based on characterization, not tested in production.
2. Refer to the note and caution paragraphs above the table.
3. The oscillator selection can be optimized in terms of supply current using an high quality resonator with small R
S
value for
example MSIV-TIN32.768 kHz. Refer to crystal manufacturer for more details
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 and it can vary significantly with the crystal manufacturer
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