STM32F411 HSE Ceramic Resonator external resistor value

[Timothee]

Hello everyone,

I'm current creating my first STM32 design using STM32F411 and have a need for the USB function on the MCU. The datasheet states that it requires a 48 MHz clock generated by a PLL connected to the HSE oscillator.

And I've currently chosen the CSTNE8M00G520000R0 ceramic resonator by muRata with built in capacitors for HSE.

Now with my understanding of an2867, I need to calculate the external resistor value based on ESR for crystal based designs.

Based on this post, it seems that ceramic resonator require external resistor, too.

However, I couldn't seem to find the ESR or maximum DL value on the webpage or datasheet of the ceramic resonator.

So my question is if I need an external resistor, and if so, what value should be?

 

Sorry if I'm not clear enough and thanks in advance.

[STOne-32]

Dear @Timothee ,

Welcome in STCommunity !  

If in your application USB is required , I do not recommend to use that Ceramic resonator as you can see it’s datasheet it has 0,5% of precision at initial state . USB requires 500 PPM maximum of precision, So I suggest to use standard quartz of 8 or 16 , 24  etc MHz .

You need to have CL1 and CL2 capacitors and without a need for Rext . Very rare saw at our customers design .

Hope it helps you .

Regards, STOne-32

[Timothee]

Understood, thanks for the quick response.