How to obtain 17 MHz for STM32F100?

Anand Krishnan · ‎2017-04-05

Posted on April 05, 2017 at 15:55

In STM32F100 If we are connecting 32MHz external Clock, How do we obtain 17MHz System clock?

By using PREDIV and PLLMUL

#pll #clock

Amel NASRI · ‎2017-04-05

Posted on April 05, 2017 at 16:18

Hi

krishnan.anand

‌,

Please note that the maximum allowed value for external clock source is 24 MHz (refer 'External clock source characteristics' sections in

http://www.st.com/content/ccc/resource/technical/document/datasheet/dd/87/fd/2a/fb/3f/48/5c/CD002517pdf/files/CD002517pdf/jcr:content/translations/en.CD002517pdf

).

I advise you to use

http://www.st.com/content/st_com/en/products/development-tools/software-development-tools/stm32-software-development-tools/stm32-configurators-and-code-generators/stm32cubemx.html

that should help you to calculate PLL mul and div factors depending on your input clock source and the expected output value.

-Amel

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Tesla DeLorean · ‎2017-04-05

Posted on April 05, 2017 at 16:20

It might be challenging as the options are limited, and 17 is a prime number

You'd have more options with an F2 or F4 part.

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AvaTar · ‎2017-04-05

Posted on April 05, 2017 at 16:24

Perhaps with a PLL factor of two, if you manage to find a 8,500 MHz quartz.

But as said, never from 32MHz.