Doubt flash memory Nor retention

[ÍStef.1]

NOR flash memory chips behave the same as other types of flash memory. If I energize NOR flash once a year, will it prevent any data loss? The datasheet says retention 20 years. If I energize it after 19 years, will it prolong data retention?
in my case the storage temperature varies between 33-36C, write cycles are few, I use it more for reading
the chip is ST M29W640FT 70N6H in its datasheet it says that the retention is for 20 years. I don't know if the storage temperature is the data retention temperature or the flash chip storage temperature. Maximum rating is -65 to 150 °C

in my case the storage temperature varies between 33-36C and 15 eraser and no more what is the average number of years of 100% data retention? my chip in pcb some storage

[TDK]

Per the datasheet, the manufacturer guarantees data retention for 20 years at operating conditions, which includes the range of -40 C to 85 C. Storage temperature is listed under absolute maximum ratings. Devices should not be at absolute maximum ratings, as stated in the datasheet.

In reality, data will be retained far longer than 20 years under less stressing ambient conditions (i.e. lower than 85 C).

It is difficult for the manufacturer to estimate average lifespan when the lifespan is over 20 years.

[Peter BENSCH]

Well, the M29W were once a product of ST, but the entire product line was spun off in 2007 as NUMONYX, which was later bought by Micron. But even there they have obviously been obsolete for a long time.

However, NOR Flash does not have the problem of NAND Flash, which has to be refreshed more or less regularly in order to preserve the data. As long as the last write operation was completed correctly, you shouldn't have a data problem in this respect. The 20 years mentioned apply to the full temperature range, with your moderate 33...36°C you can assume significantly more. However, I no longer have FIT data for these very old devices, so I cannot calculate the service life at your temperature (keyword Arrhenius).

The storage temperature is the storage temperature of the flash chip without being powered. The ambient temperature, usually -40...+85°C, is probably more interesting for your application.

Hope that answers a bit your questions?

Regards
/Peter

[ÍStef.1]

1) Does the NOR flash memory need to be energized once a year to preserve 100% of the data?

2) in the case of my mentioned chip ST M29W640FT 70N6H  and soldered on PCB, 20 years of retention is it within the mentioned temperature range or at the temperature extremes in that range?

3) 33-36C what is the average number of years of retention of all data for this chip mentioned? Currently I do not copy any new data to this chip

[Peter BENSCH]

1. As already mentioned: one successful write is sufficient for at least 20 years.

2. as @TDK also mentioned, the (minimum) 20 years mentioned apply to the full ambient temperature range, not the storage temperature range.

3. I already mentioned that you could calculate this with FIT (Failure in Time) data. However, I don't have any FIT data for the M29W640FT70N6H, so I can't make a more precise statement. However, I could well imagine (no guarantee or official statement) that 25 years or more is not a problem.

[ÍStef.1]

1) The extreme temperature data retention range for test chip are -65c to 150c or -40 to 85c?

2) my temperature ranges from 33-36c and is within the range if the temperature were lower or higher than mine the years of retention would be more or less years or any temperature within the range the years of retention will always be 20 years regardless of any temperature within the range?

3) many flash memories lose data after a few years without power, it is recommended to power up at least once a year, in the case of flash memory the retention is 20 years without power or 20 years by powering up frequently

[Peter BENSCH]

Your questions seem to go back to the same problem you discussed with @Tesla DeLorean in 2021.

However, you want statements on devices that have been cancelled for ages. Everything that can be said now has already been said.

By the way, I would like to clarify another misconception: even with NAND flash (what you call other types of flash), it is not enough to just switch it on, i.e. apply voltage, it must be actively addressed by a host so that the cells are refreshed.

[TDK]

1+2) Already answered previously.

3) Data sheet says 20 years minimum, no restrictions. I have no reason to doubt this.

[ÍStef.1]

Does NOR flash not lose data if it remains unpowered for 20 years?

Does 10 degrees cooler than 85C double the data retention time?

the number of writes influences the retention time, in my case files were copied to this chip a maximum of 10 times after just one annual read