Crystal drive level for STM32F030

[ECost]

Hello, I am trying to select a crystal for a design but I am having some difficulty. The data sheet provides little information and AN2867, too much but not very useful IMO. AN2867 depends on taking measurements to determine DL and I do not have the required resources. Right now I am working o the schematics.

I am prone to picking a HCS-49S-ish part as they support high drive levels but, before doing it, I would like to know if a crystal of 100uW (most of smaller SMD parts) would work. The layouts of the some of the evaluation boards show a not loaded HCS-49-ish but, unfortunately, whatever the crystal meant for the position, there is not specifics on the BOM.

EDIT: I forgot to mention the crystal is for the HSE, 8MHz.

I would appreciate some specific guidance about this matter, if possible.

Thanks in advance.

[Uwe Bonnes]

If you care for lowest power consumption, highest precission, lowest drift, wide temperature range and highest manufacturing yield, you need to understand AN2867 and select an appropriate quarz. If some more ppm of frequency offset and drive don't harm you, use a standard quarz with "standard" capacitors and things will work for most requirements in most cases.

[ECost]

Hello, Uwe,

Frequency accuracy, precision and stability as well as the lowest possible power consumption are not critical in my application . In fact, I am adding the cristal just in case as the internal oscillator may suffice.

It is the first time I have to dig into such a detailed analysis to have a crystal oscillator to work. Usually, data sheets indicate requirements such as ESR, load capacitance and maximum drive level.

I doubt the typical users of STM32F0 needs to extract every uW and every ppm out of the HSE oscillator and they would benefit from having typical values for guidance. Those requiring higher specs would then be directed to AN2867. Of course, this is just my opinion.

I tried to play with the formulae on the AN to estimate DL. The problem is I have no idea of what is the level of the signal on the input side of the oscillator, which is required to estimate the current/power through the crystal. I do not have a STM32F0 board at the moment or a low capacitance probe available at the moment. Does anyone know this level for a typical 8MHz crystal?