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Background

I am a software developer trying to calculate data retention rate of a NAND memory ic. I have minimal knowledge/experience with electronics.

I have a constraint on data retention, 15 years. I am trying to calculate data retention rate of a 256 MB SLC NAND with ECC. This NAND will be used alongside with a host controller for a custom module.

I have the following application parameters:

  • Operating temperature range is commercial, 0 - 40 Centigrade Celsius.
  • 512 bytes of data will be written to a fixed address range sequentially on NAND 3 times per day
  • 31 Bytes of data will be written to a fixed address range sequentially on NAND 10 times per day
  • 512 bytes of data will be written to a fixed address range sequentially on NAND once daily.

Issue

Datasheet for NAND IC includes just a graph with logarithmic scales under Reliability:

enter image description here

Also I found the following article: Understanding Life Expectancy of Flash Storage, unfortunately I cant make a connection between parameters mentioned in article and my application parameters.

Questions

What is Write/Erase Endurance Cycles?

How is related to application parameters mentioned above?

Is there a formula to calculate data retention rate based on application parameters mentioned above?

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  • \$\begingroup\$ You need to write < 2.56kB per day to a 256MB store. That means it will take 100,000 days or well over 250 years before you have filled it once and have to worry about even a single erase cycle. (If it's written one page at a time and you only pack 31 bytes per page, then you lose some of that, of course). \$\endgroup\$
    – user16324
    Commented Sep 11, 2020 at 11:52
  • \$\begingroup\$ @BrianDrummond I am writing starting from where previous writes end. So I am writing on the same page until it is full. Does this mean that everytime I try to write, I am erasing the page and rewrite with appended data? Can you elaborate on how to calculate if this the case? \$\endgroup\$
    – raidensan
    Commented Sep 11, 2020 at 12:14
  • 2
    \$\begingroup\$ No, multiple writes to different locations in the same page don't involve erases. \$\endgroup\$
    – user16324
    Commented Sep 11, 2020 at 12:21

1 Answer 1

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You didn't link the device datasheet, but a typical SLC NAND will use 512 byte pages, giving a total of 524288 pages in a 256 MB device. You are writing 14 pages per day, so it will take 102 years to completely fill the device.

Since your design spec is only 15 years, you will never erase anything and could actually use memory that was not reprogrammable if such were available.

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