M27W402 View Datasheet(PDF) - STMicroelectronics
Part Name
Description
Manufacturer
M27W402 Datasheet PDF : 15 Pages
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M27W402
On-Board Programming
The M27W402 can be directly programmed in the
application circuit. See the relevant Application
Note AN620.
Electronic Signature
The Electronic Signature (ES) mode allows the
reading out of a binary code from an EPROM that
will identify its manufacturer and type. This mode
is intended for use by programming equipment to
automatically match the device to be programmed
with its corresponding programming algorithm.
The ES mode is functional in the 25°C ± 5°C am-
bient temperature range that is required when pro-
gramming the M27W402. To activate the ES
mode, the programming equipment must force
11.5V to 12.5V on address line A9 of the
M27W402 with VPP = VCC = 5V. Two identifier
bytes may then be sequenced from the device out-
puts by toggling address line A0 from VIL to VIH. All
other address lines must be held at VIL during
Electronic Signature mode. Byte 0 (A0 = VIL) rep-
resents the manufacturer code and byte 1
(A0 = VIH) the device identifier code. For the
STMicroelectronics M27W402, these two identifier
bytes are given in Table 4 and can be read-out on
outputs Q7 to Q0.
Note that the M27W402 and M27C4002 have the
same identifier bytes.
ERASURE OPERATION (applies to UV EPROM)
The erasure characteristics of the M27W402 are
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 fluo-
rescent lighting could erase a typical M27W402 in
about 3 years, while it would take approximately 1
week to cause erasure when exposed to direct
sunlight. If the M27W402 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 M27W402 window to prevent unintentional
erasure. The recommended erasure procedure for
the M27W402 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 era-
sure time with this dosage is approximately 15 to
20 minutes using an ultraviolet lamp with 12000
µW/cm2 power rating. The M27W402 should be
placed within 2.5cm (1 inch) of the lamp tubes dur-
ing the erasure. Some lamps have a filter on their
tubes which should be removed before erasure.
9/15
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