Posted on May 17, 2011 at 13:37Hello All,
I'm actually working on STM32F107 in an Ethernet application that requires a 25 Mhz crystal
I used AN2867 as a reference for the quartz selection but I found some problem in following the indications about the selection of REXT.
The STM3210C evaluation board is fitted with an HOSONIC quartz ( whose characteristics are summarized in table 9 at pag. 16 of AN2867) with a 220 Ohm REXT (R63).
If I perform the gain margin check including REXT as indicated at page 13 of the AN2867, it turn out that the gain margin is 3.3 < 5 and so the oscillation startup criteria is not satisfied. Can someone help me about this ?
Can someone provide some suitable pn in 3.2x2.5mm or 5x3.2 mm case ?
Thanks in advance !!
