M48Z09PC datasheet(10/13 Pages) STMICROELECTRONICS

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Calculating Storage Life

The following formula can be used to predict stor-

age life:

{[(TA1/TT)/SL1]+[(TA2/TT)/SL2]+...+[(TAN/TT)/SLN]}

where,

– TA1, TA2, TAN = time at ambient temperature

1, 2, etc.

– TT = total time = TA1+TA2+...+TAN

– SL1, SL2, SLN = storage life at temperature 1,

2, etc.

For example an M48Z09,19 is exposed to tempera-

tures of 55

°C or less for 8322 hrs/yr, and tempera-

tures greater than 60

°C but less than 70°C for the

remaining 438 hrs/yr. Reading predicted t1% values

from Figure 9,

– SL1

≅ 200 yrs, SL2 = 28 yrs

– TT = 8760 hrs/yr

– TA1 = 8322 hrs/yr, TA2 = 438 hrs/yr

Predicted storage life

≥

{[(8322/8760)/200]+[(431/8760)/28]}

or 154 years.

As can be seen from these calculations and the

results, the expected life time of the M48Z09, 19

should exceed most system requirements.

Estimated System Life

Since either storage life or capacity consumption

can end the battery’s life, the system life is marked

by which ever occurs first.

Reference for System Life

Each M48Z09,19 is marked with a nine digit manu-

facturing date code in the form of H99XXYYZZ. For

example, H995B9431 is:

H = fabricated in Carrollton, TX

9 = assembled in Muar, Malaysia,

9 = tested in Muar, Malaysia,

5B = lot designator,

9431 = assembled in the year 1994, work week 31.

AI01399

TEMPERATURE (Degrees Celsius)

t50% (AVERAGE)

t1%

Figure 9. Predicted Battery Storage Life versus Temperature

10/13

M48Z09, M48Z19

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