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https://designers-guide.org/forum/YaBB.pl Design >> RF Design >> Hooking up VCO and prescaler https://designers-guide.org/forum/YaBB.pl?num=1107802271 Message started by gogomi on Feb 7th, 2005, 10:51am |
Title: Hooking up VCO and prescaler Post by gogomi on Feb 7th, 2005, 10:51am Hi, I am working on a fractional-N PLL design and I am having trouble with the interface from VCO to prescaler. I used a complementary LC-VCO in my design, which has a 1/2 Vdd DC bias voltage at the output, and I used CML latches in the prescaler. If I hook them up directly, it looks the DC voltage from VCO puts the prescaler latches on all the time. I don't know if there is a good way to solve this kind of problem without degrading the performance too much. Thank you for your help! gogomi |
Title: Re: Hooking up VCO and prescaler Post by DReynolds on Apr 14th, 2005, 5:59am Gogomi, I am not sure I understand your problem: what is your vco output swing when you have the latches attached? Worst case, why not ac couple and set your dc level on the latches yourself? David Reynolds |
Title: Re: Hooking up VCO and prescaler Post by wued on Apr 21st, 2005, 10:48pm Hi, I donot think it is a good way to connected them together directly,why not use a buffer.The buffer may be a CML one,there is not level problem. |
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