How to calculate the vco input capacitor for HMC732?
Worst case (lowest) you can assume that it's about 15pF. This capacitance will vary across the tuning band of the VCO, with more capacitance at the lower end of the band. For PLL loop filter calculations you will want an external shunt capacitor about 1000x the input capacitance of the VCO, such that as the VCO tunes, it will not have any noticeable impact on the last pole of the filter.
Can you elaborate on your question?
I means, when I design the loop filter, I need to know the input capacitor of the VCO.
So, what's the input capacitor of HMC732?
It's 1.4pF or 15pF(1.4pF//13.6pF)?
Got it. Thank you so much.
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