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Design >> RF Design >> loop filter for a PLL design with Frac-N synthesizer and MMIC VCO
https://designers-guide.org/forum/YaBB.pl?num=1236694380

Message started by slate on Mar 10^th, 2009, 7:13am

Title: loop filter for a PLL design with Frac-N synthesizer and MMIC VCO
Post by slate on Mar 10^th, 2009, 7:13am

Hi everyody guys,

I'm designing a PLL, operating in the range (2-6 GHz), using a SKY72302 dual Frac-N synth, an Hittite wideband MMIC VCO (HMC586LC4B) and a fourth order passive loop filter; the problem is that the VCO's data sheet doesn't show the exact Kvco gain ( i only have a plot thet describes Vtune VS Freq and i can estimate something around 300 MHz/V) and i dont know the exact charge pump current.

Is there anyone has already used these components and can tell me the Icp i have to set?
Is the typical value (found on several papers) of 1mA correct for my application?

I hope my description is clear enough, contact me if u have more questions ;)

ps. the other parameters used for the designing of the loop filter are:
UGBW = 80 KHz, Fvco = 3.8 GHz, Fref = 24 MHz.

Best regards, Slate

Title: Re: loop filter for a PLL design with Frac-N synthesizer and MMIC VCO
Post by chenyan on Apr 16^th, 2009, 6:25am

Hi Slate,

I think you question is really difficult to answer since I don't know where you are stuck.

I would suggest you read some pll books (chapters or even application notes), get all the formulae at hand. Then post your questions when you find some thing difficult to solve or understand.