Need recommendation for EPROM eraser

[brouhaha]

(09-07-2023 07:38 PM)JoeG Wrote:  It looks interesting. I just don’t know the detailed specifics of what he ordered, and what power source he uses (milliwatts?). So I asked those questions via YouTube.

Seven years ago purchased a 1W short wave UV LED (dangerous!), and it took somewhere around 15 minutes to erase a microcontroller that normally took 45 minutes in a Logical Devices Ultralite (as shown by someone else earlier in this thread). The particular microcontroller part was an outlier for erase times. Most normal EPROMs erase much faster in the Ultralite, though there is considerable variation between vendors, part numbers, and even individual chips.

Intel specified the integrated dose to erase the original 2716 EPROM (circa 1977) at 15Ws/cm^2 at 253.7nm (a mercury emission line, used by common germicidal bulbs). The exact wavelength doesn't matter, though longer wavelengths may take longer. Wavelengths between 200nm and 300nm work well. Note that you won't get perfect coupling of the light source to the die, and you will be illuminating a larger area than just the die, so a 1W UV point source over the EPROM window will not erase the 2716 EPROM in 15s.

You should erase EPROMs longer than the absolute minimum time that satisfies an erasure check, because at that point the bits aren't actually FULLY erased. The floating gate memory cell is analog, and is amplified and compared to a threshold. At the minimum time that the part reads as erased, some of the floating gates have almost enough charge to read as programmed. You have to have some margin against temperature and voltage variations, and other unpredictable causes of variation.

Some people have used unfiltered quartz envelope xenon flash tubes to erase EPROMs with a single flash. It works, but repeated use damages the chip in fewer erase cycles than more conventional erasers.

WARNING:

Short wave UV can burn your eyes and skin, and cause DNA damage, which is how it kills bacteria. Never operate a shortwave UV (under 300nm) light source except in a light-sealed container. All UV erasers should have a safety interlock switch that cuts power when the enclosure is opened.