Hi there,
I just started playing around with the eval board and the bias current and load capacitance settings do not make sense to me.
Could somebody provide the datasheet or information on the 25 MHz Xtal used on the eval board? I do not have a great microscope, but I see the NDK logo, "25.000 MHz" and ".96", and a "59". I would be very grateful for a hint to the part number, so that I can figure this out for the target application.
Kind thanks,
Jan
Dear Hao,
Your response was a fantastic help! Now understanding the specified CL = 8 pF for this Xtal solved the mystery. By tuning the frequency over CL in the EVM (blue trace below), I was able to obtain 0 ppm crossing at around 5.8 pF. From this we can extract that the C_stray on the EVM to be around 2.2 pF (assuming here that the capacitors on the CDVE6214E-Q1 are "perfect"). With this and the tuning equation, e.g. EQ(10) provided by Statek in their excellent Tech note 30, and assuming a capacitance ratio Cr = C1/Co of 0.004, the results agree well with theory.
Many kind thanks for your help! This has been critical in understanding the CDCE6214E-Q1 for my work and the decision designing it in.
Kind regards,
Jan
