K60 Clock Requirements

Carl_7 · ‎07-05-2012

I am configuring my board to use an external 25MHz crystal for the main clock. Is it absolutlely necessary to also have a 32kHz crystal on your board even if you are not using an RTC?

comsosysarch · ‎07-05-2012

No. You do not need the 32k clock unless you specifically use it for some device module.

I've been using a custom dev board with only a 50 MHz high speed EXTAL for about 18 months no problem (well, no oscillator problems).

You can leave XTAL32 float, we've grounded EXTAL32 thru a 10M resistor, but I think that is just overkill for possible noise reduction, I do not believe it is required to actually do that. In fact it might be better without. I think the designer just did it so Altium would not complain it was a floating "input".

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comsosysarch · ‎07-05-2012

No. You do not need the 32k clock unless you specifically use it for some device module.

I've been using a custom dev board with only a 50 MHz high speed EXTAL for about 18 months no problem (well, no oscillator problems).

You can leave XTAL32 float, we've grounded EXTAL32 thru a 10M resistor, but I think that is just overkill for possible noise reduction, I do not believe it is required to actually do that. In fact it might be better without. I think the designer just did it so Altium would not complain it was a floating "input".