I am currently testing a 50MHz 3.3V CMOS oscillator in my circuit, which is connected to two pins/loads - MCU pin and Ethernet PHY pin. The oscillator is rated for 15pF output load, which I could be exceeding by a few pF perhaps. Things are working fine in my circuit and so is the Ethernet Communication.
Now, the oscillator Vcc is supplied by 3.3V. When I am observing the waveform at the output pin of the oscillator, I am getting a 4V high, 0.8V low 50MHz sine waveform. I am wondering what is causing the voltage to go to 4V when my supply vltage is 3.3V? I have a 10R resistor at the oscillator output which is provided for termination adjustment.
Note: I am testing the waveform using an oscilloscope of 100MHz bandwidth, because I don't have any other oscilloscope at hand. But I think that should actually result in lesser amplitude.
Could anyone please help me in identifying the reasons for this higher output voltage?
Let me know if I missed providing any important information required for the analysis.
EDIT: The higher voltage is irrespective of Ethernet cable connection.