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STM32F050K6U6 Datasheet, PDF (55/97 Pages) STMicroelectronics – Low- and medium-density advanced ARM™-based 32-bit MCU with up to 32 Kbytes Flash, timers, ADC and comm. interfaces
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STM32F050xx
Electrical characteristics
Figure 14. Typical application with an 8 MHz crystal
2ESONATORWITH
INTEGRATEDCAPACITORS
#,
-( Z
RESONATOR
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CON TROLLED
GAIN
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2%84 /3#?/5 4
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1. REXT value depends on the crystal characteristics.
Low-speed external clock generated from a crystal resonator
-36
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 Table 32. 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).
Table 32. LSE oscillator characteristics (fLSE = 32.768 kHz)
Symbol
Parameter
Conditions(1)
Min(2) Typ Max(2) Unit
IDD LSE current consumption
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
- 0.5 0.9
-
-
1
µA
-
-
1.3
-
-
1.6
5
-
-
gm
Oscillator
transconductance
LSEDRV[1:0]= 01
medium low driving capability
LSEDRV[1:0] = 10
medium high driving capability
8
-
15
-
-
µA/V
-
LSEDRV[1:0]=11
higher driving capability
25
-
-
tSU(LSE)(3) Startup time
VDD 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. tSU(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
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.
Doc ID 023683 Rev 1
55/97
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