Table 37. Lse Oscillator Characteristics (F Lse = 32.768 Khz) - STMicroelectronics STM32F042G4 Manual

STM32F042xx
Low-speed external clock generated from a crystal resonator
The low-speed external (LSE) clock can be supplied with a 32.768 kHz crystal resonator
oscillator. All the information given in this paragraph are based on design simulation results
obtained with typical external components specified in
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).
Table 37. LSE oscillator characteristics (f
Symbol Parameter
I LSE current consumption
DD
Oscillator
g
m
transconductance
(3)
t Startup time
SU(LSE)
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 is the startup time measured from the moment it is enabled (by software) to a stabilized 32.768 kHz oscillation is
SU(LSE)
reached. This value is measured for a standard crystal and it can vary significantly with the crystal manufacturer
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.
(1)
Conditions
LSEDRV[1:0]=00
lower driving capability
LSEDRV[1:0]= 01
medium low driving capability
LSEDRV[1:0] = 10
medium high driving capability
LSEDRV[1:0]=11
higher driving capability
LSEDRV[1:0]=00
lower driving capability
LSEDRV[1:0]= 01
medium low driving capability
LSEDRV[1:0] = 10
medium high driving capability
LSEDRV[1:0]=11
higher driving capability
V is stabilized
DDIOx
DocID025832 Rev 2
Electrical characteristics
Table 37. In the application, the
= 32.768 kHz)
LSE
(2)
Min Typ
- 0.5
-
-
-
5
8
15
25
-
(2)
Max Unit
0.9
- 1
μA
- 1.3
- 1.6
- -
- -
μA/V
- -
- -
2 - s
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