Cycling endurance

AN4434

8/17

DocID025810 Rev 3

devices specified as 4 million cycles, a word can be cycled 4 million times).

1.2.4

Overall number of write cycles

When evaluating the cycling performances of an application, it must be stressed out that the

number of cycles can be defined either for each memory cell or for the overall number of

cycles decoded by the whole memory:

–

the max cycling value defined in the datasheet is the max number of cycles for

each byte

–

the overall number of cycles is the number of cycles correctly decoded and

executed by the device, spread over all addressed locations in the memory.

The characterization trials performed on automotive CMOS F8H products

(MXXxxx-A125/A145) equal or larger than 32Kbit have demonstrated that the overall

number of write cycles exceeds 128 million cycles, at 25°.

1.3

Cycling strategy in the end application

In order to ensure the safest EEPROM cycling conditions, it is strongly recommended to

evaluate the number of write cycles and the relative temperature profile of the cycling

performed by the EEPROM during the life of the application, that is:

Number of cycles at temp i

()

Max Number of cycles specified at temp i

()

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

1

≤

i1

=

n

∑

•

define the main temperature ranges at which the EEPROM is operating in the end

application,

•

for each temperature range, estimate the number of write cycles executed for each

data block,

•

for each data block (with different cycling profiles), calculate the cumulated cycling

effect using the following equation or Table 3.

1. The table can be adapted according to the temperature profile by taking care of putting down the maximum

cycling for each temperature

Temperature

2. w,x,y and z are forecast number of cycles for a specific data block

% of the max cycling value specified in Table 2

25°C

w

(w/4M) x 100 = a %

55°C

x

(x/2.3M) x 100 = b %

85°C

y

(y/1.2M) x 100 = c %

125°C

z

(z/600K) x 100 = d %

Total

w + x + y + z

(a + b + c + d) %