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

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.