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select crystal to STM32F207

Question asked by on Sep 4, 2014
Latest reply on Nov 2, 2015 by Clive One
Hello,I am a student that is designing  a prototype with STM32F207VC. I'm trying to choose a 25 MHz crystal oscillator to have ethernet, with AN2876 guide. I see in this guide the recommend crystal STS25ASM , but when I do the calculations of the guide the results are not valid.The external capacitors values are 30 pF, and the result of the gain margin, assuming the gm is 5, is 2.15. Why this crystal is recommend?Other question, which is the typical value of vpp value in calculating drive level?thank you,