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PDF M27C256B Data sheet ( Hoja de datos )
| Número de pieza | M27C256B | |
| Descripción | 256 Kbit (32Kb x 8) UV EPROM and OTP EPROM | |
| Fabricantes | STMicroelectronics | |
| Logotipo |  |
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M27C256B
256 Kbit (32Kb × 8) UV EPROM and OTP EPROM
Feature summary
■ 5V ± 10% supply voltage in Read operation
■ Access time: 45ns
■ Low power consumption:
– Active Current 30mA at 5MHz
– Standby Current 100µA
■ Programming voltage: 12.75V ± 0.25V
■ Programming time: 100µs/Word
■ Electronic signature
– Manufacturer Code: 20h
– Device Code: 8Dh
■ ECOPACK® packages available
28
1
FDIP28W (F)
28
1
PDIP28 (B)
PLCC32 (C)
May 2006
Rev 2
1/24
www.st.com
1
1 page  
M27C256B
1 Summary description
Summary description
The M27C256B is a 256 Kbit EPROM offered in the two ranges UV (ultra violet erase) and
OTP (one time programmable). It is ideally suited for microprocessor systems and is
organized as 32,768 by 8 bits.
The FDIP28W (window ceramic frit-seal package) has a transparent lid which allows the
user to expose the chip to ultraviolet light to erase the bit pattern. A new pattern can then be
written to the device by following the programming procedure.
For applications where the content is programmed only one time and erasure is not
required, the M27C256B is offered in PDIP28 and PLCC32 packages.
In order to meet environmental requirements, ST offers the M27C256B in ECOPACK®
packages.
ECOPACK packages are Lead-free. The category of second Level Interconnect is marked
on the package and on the inner box label, in compliance with JEDEC Standard JESD97.
The maximum ratings related to soldering conditions are also marked on the inner box label.
ECOPACK is an ST trademark. ECOPACK specifications are available at: www.st.com.
Figure 1. Logic diagram
VCC VPP
15
A0-A14
8
Q0-Q7
E M27C256B
G
VSS
AI00755B
5/24
5 Page 
M27C256B
Device operation
2.10
Erasure operation (applies for UV EPROM)
The erasure characteristics of the M27C256B is such that erasure begins when the cells are
exposed to light with wavelengths shorter than approximately 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 M27C256B in about 3 years, while it would take approximately 1 week to
cause erasure when exposed to direct sunlight. If the M27C256B 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 M27C256B window to prevent unintentional erasure. The recommended
erasure procedure for the M27C256B is exposure to short wave ultraviolet light which has
wavelength 2537Å. 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 dosage is approximately
15 to 20 minutes using an ultraviolet lamp with 12000 µW/cm2 power rating. The M27C256B
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.
Table 2. Operating modes(1)
Mode
E
Read
Output Disable
Program
Verify
Program Inhibit
Standby
Electronic Signature
VIL
VIL
VIL Pulse
VIH
VIH
VIH
VIL
1. X = VIH or VIL, VID = 12V ± 0.5V.
Table 3. Electronic signature
Identifier
A0 Q7 Q6
Manufacturer’s
Code
VIL 0
0
Device Code
VIH 1
0
G
VIL
VIH
VIH
VIL
VIH
X
VIL
Q5 Q4
10
00
A9
X
X
X
X
X
X
VID
Q3 Q2
00
11
VPP Q7-Q0
VCC Data Out
VCC Hi-Z
VPP Data In
VPP Data Out
VPP Hi-Z
VCC Hi-Z
VCC Codes
Q1 Q0 Hex Data
00
20h
0 1 8Dh
11/24
11 Page | ||
| Páginas | Total 24 Páginas | |
| PDF Descargar | [ Datasheet M27C256B.PDF ] | |
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