stm32 with 32 pins with FDCAN but without HSE?

[ricardos]

Hello

Im developing a CAN Bus node and with space constrains, so i ve looked in stm32 products and a qnf32 packages looked perfect for example stm32G0B1 has FDCAN. 

The problem...These QFN32 dont expose HSE pins. I just can use HSI with 16 MHz +- 1% wich is not reliable for FDCAN, especially for industrial applications with many nodes. 

I dont understand why the mcu hás 2 FDCAN peripherals if theres no reliable clock to Run them.

Im i missing some thing here? 

At are my alternatives? I now that QFN48 hás HSE, but i dont need só much io and the packages is bigger.

Help here

[TDK · Accepted solution]

> I dont understand why the mcu hás 2 FDCAN peripherals if theres no reliable clock to Run them.

> Im i missing some thing here? 

PC14 can be used as OSC_IN in HSE bypass mode and fed with a clock signal. Use a TCXO rather than a crystal.

[ricardos]

Thank you TDK. 

Never did that bypass and never used an TCXO. I'm civil engineer...

Do you have a schematic on how to connect a TCXO to the stm32 MCU with 32 pins? Do I need to connect something to OSC_EN pin?

Thanks a lot

[TDK]

A TXCO outputs a clock as a square wave. Connect the output to the OSC_IN pin. That's it. OSC_EN is not needed.

[ricardos]

Ok. Thanks. Beyond 100nF on vcc do I need a resistor on the osc line like
33 ohm? Can I neglect this? I think the idea is to reduce emi!