M27C512
Erasure operation (applies for UV EPROM)
3
Erasure operation (applies for UV EPROM)
The erasure characteristics of the M27C512 is such that erasure begins when the cells are
exposed to light with wavelengths shorter than approximately 4000 Å. It should be noted
that sunlight and some type of fluorescent lamps have wavelengths in the 3000-4000 Å
range.
Research shows that constant exposure to room level fluorescent lighting could erase a
typical M27C512 in about 3 years, while it would take approximately 1 week to cause
erasure when exposed to direct sunlight. If the M27C512 is to be exposed to these types of
lighting conditions for extended periods of time, it is suggested that opaque labels be put
over the M27C512 window to prevent unintentional erasure. The recommended erasure
procedure for the M27C512 is exposure to short wave ultraviolet light which has wavelength
2537 Å. The integrated dose (i.e. UV intensity x exposure time) for erasure should be a
minimum of 15 W-sec/cm
2
. The erasure time with this dosage is approximately 15 to 20
minutes using an ultraviolet lamp with 12000 µW/cm
2
power rating. The M27C512 should be
placed within 2.5 cm (1 inch) of the lamp tubes during the erasure. Some lamps have a filter
on their tubes which should be removed before erasure.
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STMICROELECTRONICS [ STMICROELECTRONICS ]
