M48Z08-150PC1 查看數據表（PDF） - STMicroelectronics
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M48Z08-150PC1 Datasheet PDF : 18 Pages
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M48Z08, M48Z18
Cell Storage Life
Storage life is primarily a function of temperature.
Figure 9 illustrates the approximate storage life of
the M48Z08/18 battery over temperature. The re-
sults in Figure 9 are derived from temperature
accelerated life test studies performed at SGS-
THOMSON. For the purpose of the testing, a cell
failure is defined as the inability of a cell stabilized
at 25°C to produce a 2.4V closed circuit voltage
across a 250 kΩ load resistor. The two lines, t1%
and t50%, represent different failure rate distribu-
tions for the cell’s storage life. At 70°C, for example,
the t1% line indicates that an M48Z08/18 has a 1%
chance of having a battery failure 28 years into its
life while the t50% shows the part has a 50% chance
of failure at the 50 year mark. The t1% line repre-
sents the practical onset of wear out and can be
considered the worst case Storage Life for the cell.
The t50% can be considered the normal or average
life.
Calculating Storage Life
The following formula can be used to predict stor-
age life:
1
{ [ (TA 1/TT)/SL 1] +[ (TA 2/TT)/SL 2] +...+[ (TA N/TT)/SL N] }
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 M48Z08/18 is exposed to tem-
peratures of 55°C or less for 8322 hrs/yr, and
temperatures 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 ≥
1
{[(8322/8760)/200]+[(431/8760)/28]}
or 154 years.
As can been seen from these calculations and the
results, the expected lifetime of the M48Z08/18
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 M48Z08/18 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.
POWER SUPPLY DECOUPLING and UNDER-
SHOOT PROTECTION
ICC transients, including those produced by output
switching, can produce voltage fluctuations, result-
ing in spikes on the VCC bus. These transients can
be reduced if capacitors are used to store energy,
which stabilizes the VCC bus. The energy stored in
the bypass capacitors will be released as low going
spikes are generated or energy will be absorbed
when overshoots occur. A ceramic bypass capaci-
tor value of 0.1µF (as shown in Figure 10) is
recommended in order to provide the needed filter-
ing.
In addition to transients that are caused by normal
SRAM operation, power cycling can generate
negative voltage spikes on VCC that drive it to
values below VSS by as much as one Volt. These
negative spikes can cause data corruption in the
SRAM while in battery backup mode. To protect
from these voltage spikes, it is recommeded to
connect a schottky diode from VCC to VSS (cathode
connected to VCC, anode to VSS). Schottky diode
1N5817 is recommended for through hole and
MBRS120T3 is recommended for surface mount.
Figure 10. Supply Voltage Protection
VCC
0.1µF
VCC
DEVICE
VSS
AI02169
10/18
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