STM32F429 HSE Crystal Amplitude

[ralphj]

Posted on April 13, 2016 at 17:00

Has anyone ever had any problems with the amplitude of a clock signal when using an external crystal in HSE mode?

I have a board that I built that oscillates reliably and accurately, but the amplitude of the signal is too small.  It is centered about the midpoint voltage of 3.3, about 1.7 volts.  However, the peaks of the wave only reach about half a volt above and below the midpoint.  The DISCO board crystal is centered the same, but practically reaches the rails.  Playing with the values of the external capacitors has virtually no effect on the amplitude.  Are there any hardware or software configurations that would cause this.  Almost seems like the inverter in the microcontroller doesn't have the right supply, but I'm not sure how that could be. #stm32-crystal-clock

[Mark Edwards]

Posted on April 14, 2016 at 01:35

Application note AN2867 may help.

http://www.st.com/st-web-ui/static/active/en/resource/technical/document/application_note/CD00221665.pdf?s_searchtype=keyword