CD74ACT540: How to convert reliability data

Sean Lee26

Prodigy 40 points

Part Number: CD74ACT540

Hi Everyone.

I have a question about the reliability data which are provided from the TI as the attached image below.

On the table, the confidence level is 60% and I want to convert to 90% or 95%.

Can anybody tell me how can I convert confidence level to get the corresponding MTBF or FIT values.

Thanks

Sean

over 5 years ago

0 Emrys Maier over 5 years ago

TI__Guru* 96681 points

Hi Sean,

There's a calculator at this link that you can use to estimate 90% confidence level DPPM. The equation used is located at the bottom of the page.

At 90%, the DPPM is estimated to be 5233 for the CD74ACT540E.

0 Sean Lee26 over 5 years ago in reply to Emrys Maier

Prodigy 40 points

Hi. Emrys

Thank you for your reply...

But still don't know how I can convert MTBF and FIT value using converted DPPM value...

Can you describe it for me if you know??

Thanks again..

Sean

0 Emrys Maier over 5 years ago in reply to Sean Lee26

TI__Guru* 96681 points

FIT := Failure In Time
MTBF := Mean Time Between Failure
DPPM := Defective Parts Per Million

26.5 FIT indicates that 26.5 failures will occur over 10^9 operating hours (~100000 years)

And MTBF of 3.77*10^7 hr tells us that failures are likely to have a spacing of ~4300 years.

The conversion between these two is:

10^9 / FIT = MTBF

Remember that the values are measured in 'hours' and you have to convert to years:

years ~= hours / (24 * 365)

For DPPM, this is really a measurement of ELFR (Early Life Failure Rate), and isn't exactly the same thing as the above mentioned values... I haven't been able to find a direct conversion, but I'll ask around and see if I can find something for you.

0 Emrys Maier over 5 years ago in reply to Emrys Maier

TI__Guru* 96681 points

Hey Sean,
I just wanted to let you know that I haven't given up looking for this. I'm currently waiting to hear back from some of my contacts in the reliability/quality team.

0 Emrys Maier over 5 years ago in reply to Emrys Maier

TI__Guru* 96681 points

Hey Sean,
It looks like there's no direct conversion - it's possible to make a bunch of assumptions and kind of get an estimation from one to the other, but one type of test is for early life failure (ie defective parts) while the other tests for failure over time of otherwise good parts.

Logic

Logic forum

CD74ACT540: How to convert reliability data