deh_fuhrer said:
you'll still have the option left to use three flip-flops as synchronizer(generally used for very high frequency aplication when 2 flop is also metastable)..
Does three flops really help?
Suppose the frequency is very high (like you said), and it takes more than 1 cycle for the signal to settle, then the signal going into the 2nd flop will still be metastable.
As a result, the 2nd flop will also send out a metastable signal to 3rd flop, and just like the metastable signal that came out of the 1st flop, this 2nd metastable signal will take more than one cycle to settle, so the signal will still be metastable when it arrives at the 3rd flop.
So, adding a flop does not help, right?
What you need should be more time to settle (i.e. longer cycle time); putting another flop will just push the metastable signal a cycle forward.
Please correct me if I am wrong.