STM32L4 datasheet(11/33 Pages) STMICROELECTRONICS

部件名	STM32L4

功能描述	This module presentation presents the key differences between the STM32L4 and the STM32L476/L486 devices.

PDF	33 Pages

Scroll/Zoom	100%

制造商	STMICROELECTRONICS [STMicroelectronics]

网页	http://www.st.com

标志

11 / 33 page

System Clock Selection

• Switching from Low to High speed or from High to Low speed system

clock, it is recommended to use a transition state with a medium speed

clock for at least 1us.

• Clock source switching conditions:

• Switching from HSE or HSI or MSI to PLL with AHB frequency ( HCLK) higher than

80MHz.

• Switching from PLL with HCLK higher than 80MHz to HSE or HSI or MSI

• Transition state:

• Set the AHB prescaler HPRE[3:0] bits to divide System frequency by 2

• Switch system clock to PLL

• Reconfigure AHB prescaler bits to needed HCLK frequency

In STM32L4+ Series devices, it is recommended to use a

transition state while switching from Low to High speed or

from High to Low speed system clock. This slide presents

the recommended sequence for the transition state.

STM32L4 数据表(PDF) 11 Page - STMicroelectronics