MTBF & number of flops in synchronizer

[ivlsi]

Hi All,

As far as I know, MTBF depends on the number of flops, which take part in the synchronizer (as many flops in the synchronizer as better)...

Could someone explain how does it work? How number of the flops in the synchronizer affect to MTBF?

Related to MTBF, how is the "Failure" defined? What does it mean in terms of MTBF?

Thank you!

 

[wtr]

Mean time between failure(MTBF) is a measure of how reliable your system is.

The failure itself is open to interpretation. In your instance you could say a bit flip is a failure.
Fortunately the synchronizer would most likely correct itself after a few clock cycles.

When doing safety and reliability on hardware the quantity of components is a useful in getting a measure of MTBF.

Reading up on Mil-hdbk-217K could give you further insight into the world of reliability.

 

[ivlsi]

What do you mean under "bit flip"? Sampling a data transaction from '0' to '1' in the flop input and still getting '0' in the flop output?

How does the third flop in the synchronizer decrease the MTBF?

 

[wtr]

Okay......Are you talking about metastability?

Rule of thumb more flipflops prevent an undesired state.

The flipflops can be used to deglitch a signal until you know it's stable.
The flipflops can be used to stop metastability.

 

[andre_luis]

Could someone explain how does it work? How number of the flops in the synchronizer affect to MTBF?

Related to MTBF, how is the "Failure" defined? What does it mean in terms of MTBF?

In general, the calculation of the MTBF takes into account aspects of physical failure of the component of the kind irreversible (damage), but it is not entirely clear if you are considering just flaws in operation, as wesleytaylor mentioned.

 

[FvM]

"Failure" in terms of metstability means a detectable occurrence of a metastable event, can be e.g. detected as a FF output voltage not reaching a defined high or low level at sampling time. At page 5 of the appended Altera application note, a test circuit to measure metastability is suggested.