DocID16612 Rev 6

5/24

AN3101

System clock for STM8L05xxx/15xxx, STM8L162xx and STM8AL31xx/3Lxx

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System clock for STM8L05xxx/15xxx, STM8L162xx

and STM8AL31xx/3Lxx

The STM8L05xxx/15xxx, STM8L162xx and STM8AL31xx/3Lxx microcontrollers offer

different clock sources that can be used to drive the system clock:

•

16 MHz high-speed internal (HSI) factory-trimmed RC clock

•

1 to 16 MHz high-speed external (HSE) oscillator clock

•

32.768 kHz low-speed external (LSE) oscillator clock

•

38 kHz low-speed internal (LSI) low-consumption clock

The internal RC oscillators (HSI and LSI) have the advantage of providing a low-cost clock

source (no external components required). It also has a faster startup time than the external

oscillator. However, even with calibration, the internal RC oscillator frequency is less

accurate than the frequency of an external crystal oscillator or ceramic resonator.

Note:

The internal oscillator can also be used as backup source (auxiliary clock) if the external

oscillator fails.