Calculating probability of failure
For a single synchronizer Mean-Time Between Failure (MTBF) = exp ( tr / ? ) / ( T0 ??f ??a ) where a failure occurs if metastability persists beyond time tr after a clock edge
tr is the resolution time - extra time in clock period for settling
- Tclk - (tpd + TCL + tsetup)
f is the frequency of the FF clock
a is the number of asynchronous input changes per second applied to the FF
T0 and ? are constaints that depend on the FF's electrical characteristics (e.g., gain or steepness of curve)
- typical values are T0 = .4s and ? = 1.5ns (sensitive to temperature, voltage, cosmic rays, etc.).
Must add probabilities from all synchronizers in system 1/MTBFsystem = ? 1/MTBFsynch