STM32 MCO1/2 Driving a second chip XTAL input

[meir3]

Posted on August 07, 2017 at 06:36

Hello all,

In my project, I'm using the STM32F411CEU6, with a 9.6MHz External TCXO as a clock source. I would like to use the same clock to feed another chip in the board.

I was thinking of using the MCO1 or 2 in order to rout out the 9.6MHz to the other chip.

The other chip XTAL input characteristics are:

Can MCO1 or 2 drive an input load of 150k / 20pF @ 9.6MHz?

Thank you all,

Chen

#stm32f411ceu6 #mco1

[Vangelis Fortounas]

Posted on August 07, 2017 at 08:03

hello!

Yes it can drive the 9600 KHZ

At Datasheet @I/O AC characteristics,  and @Output voltage characteristics,   you can find it.

[meir3]

Posted on August 07, 2017 at 08:17

Hi Vangelis,

I did looked at the I/O AC characteristics table, but I wasn't sure that the I/O characteristics also refers to the MCO  characteristics.

Anyway, just to be sure...

If I use a 3.3V supply, and OSPEEDRy bits are ''01'', I can reach up to 12.5MHz under 50pF load?

Thanks again!

Chen

[meir3]

Posted on August 07, 2017 at 09:57

Great!  many thanks!

Chen

[Vangelis Fortounas]

Posted on August 07, 2017 at 08:42

Hello again

For every GPIO pin (except otherwise specified) the output capability is not depend from internal circuitry but from output driver circuit.

At RM0383  @6.2.10 Clock-out capability, the mco functionality, is just an alternate output function of a GPIO pin.