M27V401 View Datasheet(PDF) - STMicroelectronics

Part Name

Description

Manufacturer

M27V401

4 Mbit (512Kb x 8) Low Voltage UV EPROM and OTP EPROM

STMicroelectronics 

M27V401

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 M27V401. To activate the ES mode,

the programming equipment must force 11.5V to

12.5V on address line A9 of the M27V401, with

VPP = VCC = 5V. Two identifier bytes may then be

sequenced from the device outputs by toggling ad-

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 manufacturer

code and byte 1 (A0 = VIH) the device identifier

code. For the STMicroelectronics M27V401, these

two identifier bytes are given in Table 4 and can be

read-out on outputs Q7 to Q0. Note that the

M27V401 and M27C4001 have the same identifier

bytes.

ERASURE OPERATION (applies to UV EPROM)

The erasure characteristics of the M27V401 is

such that erasure begins when the cells are ex-

posed to light with wavelengths shorter than ap-

proximately 4000Å. It should be noted that sunlight

and some type of fluorescent lamps have wave-

lengths in the 3000-4000Å range. Research

shows that constant exposure to room level fluo-

rescent lighting could erase a typical M27V401 in

about 3 years, while it would take approximately 1

week to cause erasure when exposed to direct

sunlight. If the M27V401 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 M27V401 window to prevent unintentional era-

sure. The recommended erasure procedure for

the M27V401 is exposure to short wave ultraviolet

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

12000µW/cm2 power rating. The M27V401 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 era-

sure.

9/15

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