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sommer2
sommer2
Associate
May 23, 2017
Question

Can I use a max HSE clock 24 MHz input with a 26 MHz crystal oscillator?

  • May 23, 2017
  • 2 replies
  • 865 views
Posted on May 23, 2017 at 11:39

Hi, I'm using the STM32L152C8U6-A MCU. I want to use the high speed external clock signal (HSE). The HSE is specified for frequencies from 1-24 MHz. I have an 26 MHz c

rystal oscillator

. What happen, if I still use the HSE with my 26 MHz

c

rystal oscillator

? Can I use the clock anyway? What are the consequences of this fix? 

Thank you, best regards.

#hse #clock #stm32l152c8u6-a #oscillator
This topic has been closed for replies.

2 replies

Max
Max
ST Employee
May 24, 2017
Posted on May 24, 2017 at 05:22

If you use the HSE out of the specification:

  • there is no guaranty the oscillator will start
  • In case it does start, the oscillator may stop whenever the conditions are changing (temperature, noise, ...)
  • There might be differences from device to device regarding the oscillator behavior (some may work, some won't)
  • You may not be able to configure CubeMx for it, you will need to modify the code manually
  • It's at your own risk, I do not recommend to go in production with this
waclawek.jan
waclawek.jan
Super User
May 24, 2017
Posted on May 24, 2017 at 09:04

Max,

I believe Remo meant an external oscillator, as in HSE bypass.

Remo,

Please have a look at 6.3.6  External clock source characteristics in the datasheet.

JW

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