M27C512
ERASURE OPERATION (APPLIES FOR UV EPROM)
The erasure characteristics of the M27C512 is
such that erasure begins when the cells are ex-
posed to light with wavelengths shorter than ap-
proximately 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 ap-
proximately 1 week to cause erasure when ex-
posed 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 dos-
age is approximately 15 to 20 minutes using an ul-
traviolet 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 ]
