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STM32F412xE/G Electrical characteristics
161
possible to the oscillator pins in order to minimize output distortion and startup stabilization
time. Refer to the crystal resonator manufacturer for more details on the resonator
characteristics (frequency, package, accuracy).
The LSE high-power mode allows to cover a wider range of possible crystals but with a cost
of higher power consumption.
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.
For information about the LSE high-power mode, refer to the reference manual RM0383.
Figure 30. Typical application with a 32.768 kHz crystal
Table 41. LSE oscillator characteristics (f
LSE
= 32.768 kHz)
(1)
1. Guaranteed by design, not tested in production.
Symbol Parameter Conditions Min Typ Max Unit
R
F
Feedback resistor - - 18.4 - MΩ
I
DD
LSE current consumption
Low-power mode
(default)
--1
µA
High-drive mode - - 3
ACC
LSE
(2)
2. This parameter depends on the crystal used in the application. Refer to the application note AN2867.
LSE accuracy - -500 - 500 ppm
G
m
_crit_max Maximum critical crystal g
m
Startup, low-power
mode
--0.56
µA/V
Startup, high-drive
mode
--1.50
t
SU(LSE)
(3)
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 guaranteed by characterization and not tested in
production. It is measured for a standard crystal resonator and it can vary significantly with the crystal
manufacturer.
startup time V
DD
is stabilized - 2 - s
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