HD6475328CG Datasheet, PDF (316/459 Pages) Hitachi Semiconductor – Manual Gives a Hardware Description

17.3.4 Erasing of Data
The windowed package enables data to be erased by illuminating the window with ultraviolet
light. Table 17-7 lists the erasing conditions.
Table 17-7 Erasing Conditions
Item
Ultraviolet wavelength
Minimum illumination
Value
253.7nm
15W·s/cm²
The conditions in table 17-7 can be satisfied by placing a 12000µW/cm² ultraviolet lamp 2 or 3
centimeters directly above the chip and leaving it on for about 20 minutes.
17.4 Handling of Windowed Packages
1. Glass Erasing Window: Rubbing the glass erasing window of a windowed package with a
plastic material or touching it with an electrically charged object can create a static charge on
the window surface which may cause the chip to malfunction.
If the erasing window becomes charged, the charge can be neutralized by a short exposure to
ultraviolet light. This returns the chip to its normal condition, but it also reduces the charge
stored in the floating gates of the PROM, so it is recommended that the chip be reprogrammed
afterward.
Accumulation of static charge on the window surface can be prevented by the following
precautions:
(1) When handling the package, ground yourself. Don’t wear gloves. Avoid other possible
sources of static charge.
(2) Avoid friction between the glass window and plastic or other materials that tend to
accumulate static charge.
(3) Be careful when using cooling sprays, since they may have a slight ion content.
(4) Cover the window with an ultraviolet-shield label, preferably a label including a
conductive material. Besides protecting the PROM contents from ultraviolet light, the label
protects the chip by distributing static charge uniformly.
2. Handling after Programming: Fluorescent light and sunlight contain small amounts of
ultraviolet, so prolonged exposure to these types of light can cause programmed data to invert.
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