STM32L071X8 Datasheet, PDF (78/136 Pages) STMicroelectronics – Access line ultra-low-power 32-bit MCU ARM-based Cortex-M0+, up to 192KB Flash, 20KB SRAM, 6KB EEPROM, ADC

Electrical characteristics
STM32L071xx
Low-speed external clock generated from a crystal/ceramic resonator
The low-speed external (LSE) clock can be supplied with a 32.768 kHz crystal/ceramic
resonator oscillator. All the information given in this paragraph are based on
characterization results obtained with typical external components specified in Table 45. In
the application, the resonator and the load capacitors have to be placed as close as
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).
Symbol
Table 45. LSE oscillator characteristics⁽¹⁾
Parameter
Conditions⁽²⁾
Min⁽²⁾ Typ
Max Unit
f_LSE LSE oscillator frequency
LSEDRV[1:0]=00
lower driving capability
- 32.768 - kHz
-
-
0.5
G_m
Maximum critical crystal
transconductance
LSEDRV[1:0]= 01
medium low driving capability
LSEDRV[1:0] = 10
medium high driving capability
-
-
0.75
µA/V
-
-
1.7
t_SU(LSE)(3) Startup time
LSEDRV[1:0]=11
higher driving capability
V_DD is stabilized
-
-
2.7
-
2
-
s
1. Guaranteed by design.
2. Refer to the note and caution paragraphs below the table, and to the application note AN2867 “Oscillator design guide for
ST microcontrollers”.
3.
Gtouaarsatanbteileizdedby3c2h.7a6ra8ckteHrzizoasticoinllarteiosnulitss.rte_{SaUc(hLSeEd).}
is the startup
This value is
time measured
measured for a
from the moment it is enabled (by software)
standard crystal resonator and it can vary
significantly with the crystal manufacturer. To increase speed, address a lower-drive quartz with a high- driver mode.
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 24. Typical application with a 32.768 kHz crystal
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Note:
069
An external resistor is not required between OSC32_IN and OSC32_OUT and it is forbidden
to add one.
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