EEPROM耐用性指南(英文)(pdf 6頁)

The definition of “endurance” (as applied to EEPROMs)
contains various words and phrases that require clear
definition and understanding. As shown in the following
paragraphs, different manufacturers use different
standards. “Endurance cycling” is a test performed by
all manufacturers (and some customers) to determine
how many “write cycles” the product will achieve before
failing.
Microchip defines “endurance” as the minimum
number of write cycles the product can be subjected to
before it fails.
“Failure” is a somewhat arbitrary definition since a
device only truly fails when it no longer meets the
customer expectation and does not operate in his
system. A failure can be defined in this, the loosest of
definitions, or the most stringent of definitions (whereby
a device would fail if it did not meet any of the data
sheet parameters), as well as a wide range in between.
For example, if the device does not correctly store data
into a particular address that is not used, then the
device would work correctly for the customer but would
fail a functional test by the manufacturer. Likewise, if
the device draws more current than the data sheet
specifies after some time, but the customer application
could supply the current needed, the device would
work in the customer application but would fail a
parametric test set by the manufacturer.
Microchip uses the most stringent definition:
A failure occurs when the device fails to meet any
data sheet condition under any specified operating
condition of a temperature and voltage.
The number of devices that can fail before a particular
endurance criteria is not met is also somewhat flexible.
Even the most quality-conscious manufacturer will
occasionally have a failure, so a failure level is defined.
There are several industry standard conditions for
many types of reliability tests. For example, IEEE-Std-
1005-1998 defines a maximum cumulative failure rate
of 1%. JEDEC (The Joint Electronic Device Engineering
Council), JESD47, defines that if three lots of 77
units each have no fails (equivalent to an LTPD of 1%)
at a given endurance goal, then that goal has been……
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