M87C257-90C1 STMicroelectronics, M87C257-90C1 Datasheet - Page 10

• Manufacturer Part Number: M87C257-90C1
• Description: IC OTP 256KBIT 90NS 32PLCC
• Manufacturer: STMicroelectronics

Specifications of M87C257-90C1

• Format - Memory: EPROMs
• Memory Type: OTP EPROM
• Memory Size: 256K (32K x 8)
• Speed: 90ns
• Interface: Parallel
• Voltage - Supply: 4.5 V ~ 5.5 V
• Operating Temperature: 0°C ~ 70°C
• Package / Case: 32-PLCC
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Device operation
2.9
2.10
10/22
Electronic signature
Erasure operation (applies for UV EPROM)
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
ambient temperature range that is required when programming the M87C257.
To activate the ES mode, the programming equipment must force 11.5V to 12.5V on
address line A9 of the M87C257, with V
sequenced from the device outputs by toggling address line A0 from V
address lines must be held at V
represents the manufacturer code and byte 1 (A0 = V
= V
M87C257, these two identifier bytes are given in
to Q0.
The erasure characteristics of the M87C257 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 M87C257 in about 3 years, while it would take approximately 1 week to
cause erasure when exposed to direct sunlight. If the M87C257 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 M87C257 window to prevent unintentional erasure. The recommended
erasure procedure for the M87C257 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/cm
15 to 20 minutes using an ultraviolet lamp with 12000 µW/cm
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.
ID
, AS need not be toggled to latch each identifier address. For the STMicroelectronics
IL
during Electronic Signature mode. Byte 0 (A0 = V
2
. The erasure time with this dosage is approximately
CC
= V
PP
Table 4
= 5V. Two identifier bytes may then be
IH
) the device identifier code. When A9
and can be read-out on outputs Q7
2
power rating. The M87C257
IL
to V
IH
. All other
M87C257
IL
)