Data retention

AN4434

14/17

DocID025810 Rev 3

filters out extrinsic defaults and pushes the data retention limit far beyond the limit of the first

extrinsic failing bit.

second bit could be located in the same byte is equal to

:

–

() 64

⁄

=

Where:

–

k is the number of bits of the word (for ECCx1: 1 bytes and 4 ECC bits, this leads

to k = 12)

–

n is the number of bits of the whole memory.

byte cannot be recovered by the ECC logic).

2.3

Data retention strategy in the end application

The data retention time is defined in the datasheets with specific temperatures. In order to

ensure the safest EEPROM data retention, it is wise to evaluate the amount of time during

which the end application remains within some temperature range to evaluate the data

retention profile, that is:

Number of years at temp i

()

Max Number of years specified for temp i

()

------------------------------------------------------------------------------------

1

≤

i1

=

n

∑

•

define the time (in year) during which the EEPROM remains inside each temperature

range (that is a typical temperature profile of the end application),

•

for each temperature range, estimate the data retention value, in percentage, as

defined in the following equation or in Table 7.

Table 6. ECCx1 memories: probability that one byte is not correctly read

Memory capacity

1. ppm: part per million

16 Kbit

0.001

8 Kbit

0.001

4 Kbit

0.000

2 Kbit

0.000

1 Kbit

0.000