LDC3114-Q1: What is the difference between fit rate in the document "Functional safety information" and the fit rate in Quality, reliability & packaging data download

Florian,

Thank you for your post, and your interest in TI products.

The short answer is you should use the FIT numbers in your first table.

Some background:
The FIT data in your first table - from the LDC3114-Q1 Functional Safety FIT Rate, FMD and Pin FMA document - is based calculations specified in the industry standard IEC TR 62380 / ISO 26262 part 11 and represents the FIT rate for a billion hours of total device operation. Two extremes that represent this condition are a billion devices operating for an hour, or one device operating for a billion hours. Reality, of course is somewhere between these two extremes. For the details underlying the calculations, please see the standard.

The data in the second table are based on testing of 3777 devices over a thousand hours, for a total of 3.8 million hours of device operation, many orders of magnitude less than condition specified in the first table. For this reason, the FIT data in the second table should not be used for reliability/failure calculations. It merely serves to illustrate that the reliability of actual devices conform the standardized FIT calculations (e.g. the first table). As a counterpoint, if the measured FIT rate was above the rate presented in the first table, the device would not be released until the root cause for the failures was identified and corrected. 

I hope this helps. Please let me know if you have any questions.

Regards,
John