27C512 datasheet(8/22 Pages) STMICROELECTRONICS

8 / 22 page

M27C512

8/22

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/cm2. The erasure time with this dos-

age is approximately 15 to 20 minutes using an ul-

traviolet lamp with 12000 µW/cm2 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.

27C512 Datenblatt(PDF) 8 Page - STMicroelectronics