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STM32F051K4U6 Datasheet, PDF (60/104 Pages) STMicroelectronics – Low- and medium-density advanced ARM™-based 32-bit MCU with 16 to 64 Kbytes Flash, timers, ADC, DAC and comm. interfaces
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STM32F051x
Electrical characteristics
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 Table 37. 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 37. LSE oscillator characteristics (fLSE = 32.768 kHz)
Symbol
Parameter
Conditions(1)
Min(2) Typ Max(2) Unit
LSEDRV[1:0]=00
lower driving capability
- 0.5 0.9
IDD LSE current consumption
LSEDRV[1:0]= 01
medium low driving capability
LSEDRV[1:0] = 10
medium high driving capability
-
-
1
µA
-
-
1.3
LSEDRV[1:0]=11
higher driving capability
-
-
1.6
LSEDRV[1:0]=00
lower driving capability
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 022265 Rev 3
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