Scintera Networks Interview Question: Why do we need the "DOWN" pul... | Glassdoor

Interview Question

Analog Design Engineering Interview Sunnyvale, CA

Why do we need the "DOWN" pulse in Hogge detector? Can we

  get by not using it?
hogge phase detectors, cdr

Interview Answer

1 Answer


My answer was we don't need to use it. But we have to change our filter structure. Using UP and DOWN fit well to charge pump and passive RC filter topology. Since DOWN is always 50% duty cycle when there is data transition, it acts as a reference. However, if we took the UP pulse alone, feed it to an active filter with one pole ar zero and one zero at a non- zero frequency we preserve the loop dynamics.

Interview Candidate on Jul 6, 2010

Add Answers or Comments

To comment on this, Sign In or Sign Up.