M27V402 Ver la hoja de datos (PDF) - STMicroelectronics
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M27V402 Datasheet PDF : 15 Pages
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M27V402
Electronic Signature
posed to light with wavelengths shorter than ap-
The Electronic Signature (ES) mode allows the proximately 4000Å. It should be noted that sunlight
reading out of a binary code from an EPROM that and some type of fluorescent lamps have wave-
will identify its manufacturer and type. This mode lengths in the 3000-4000Å range. Research
is intended for use by programming equipment to shows that constant exposure to room level fluo-
automatically match the device to be programmed rescent lighting could erase a typical M27V402 in
with its corresponding programming algorithm. about 3 years, while it would take approximately 1
The ES mode is functional in the 25°C ± 5°C am- week to cause erasure when exposed to direct
bient temperature range that is required when pro- sunlight. If the M27V402 is to be exposed to these
gramming the M27V402. To activate the ES mode, types of lighting conditions for extended periods of
the programming equipment must force 11.5V to time, it is suggested that opaque labels be put over
12.5V on address line A9 of the M27V402 with the M27V402 window to prevent unintentional era-
VPP = VCC = 5V. Two identifier bytes may then be
sequenced from the device outputs by toggling ad-
sure. The recommended erasure procedure for
the M27V402 is exposure to short wave ultraviolet
dress line A0 from VIL to VIH. All other address
lines must be held at VIL during Electronic Signa-
ture mode. Byte 0 (A0 = VIL) represents the man-
ufacturer code and byte 1 (A0 = VIH) the device
identifier code. For the STMicroelectronics
M27V402, these two identifier bytes are given in
) Table 4 and can be read-out on outputs Q7 to Q0.
t(s ERASURE OPERATION (applies to UV EPROM)
uc The erasure characteristics of the M27V402 is
Obsolete Product(s) - Obsolete Prod such that erasure begins when the cells are ex-
light which has a wavelength of 2537Å. The inte-
grated dose (i.e. UV intensity x exposure time) for
erasure should be a minimum of 15 W-sec/cm2.
The erasure time with this dosage is approximate-
ly 15 to 20 minutes using an ultraviolet lamp with
12000 µW/cm2 power rating. The M27V402
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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