IQD IQOV-164-4 OCXO input impedance

The IQOV-164-4 1ppb OCXO spec sheet (order code 2443062) says it has an input impedance of >100k ohms, but I need to drive that VCO input with a 50 microamp charge pump from an HMC1031 using my Rubidium source as reference. How can I find the actual input characteristics? My other OCXOs typically have 1.5nF to ground at the VCO pin, then a 270k resistor to the varicap bias point, and 180nF to ground from there. I will be using a loop bandwidth of a few hundred milliHertz, so the 270k/180nF doesn't have a major effect, but I want to ensure my PLL characteristics don't have an unwanted pole which might cause instability, or a DC bias which might push the charge pump to the point where spurs are created.

Neil

0 Nick over 8 years ago

Hi Neil,

Interesting question. In 12 years of working in this industry your the first to ask.
The best way to answer this is perhaps to give you the input circuit for the voltage control line. Excuse my drawing skills, but here you go.

Also I note that your enquiry has gone unanswered on this forum for several months. again, I can only apologies for this, the activity on this form for us is very very low hence we missed your question.
Should you have any further enquiries I can recommend the chat function on our website, we aim to respond to enquiries on this format within seconds (Although during a few hours of the nigh it is unmanned, and we would pick up the following morning)

Good luck with your project
Nick
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