EPROM erase times and lifespan

Ethan Dicks ethan.dicks at gmail.com
Thu Jan 29 12:39:19 CST 2009


On Thu, Jan 29, 2009 at 1:16 PM, Dave McGuire <mcguire at neurotica.com> wrote:
> On Jan 29, 2009, at 10:27 AM, Jules Richardson wrote:
>> Presumably more expensive erasers do things in-place - i.e. periodically
>> do a blank-check during the erase cycle?
>
>  I've never seen nor heard of an EPROM eraser that does this, in nearly 30
> years of using EPROMs.

I have never seen that either... the ones I've worked with
professionally have had a variety of features including timers,
conductive plastic rails at 0.6" spacing for ESD reasons and easy
loading, but I've never seen any sort of eraser that applies power to
the chips in any way.

I myself did some experiments a couple of years ago at the South Pole
when I didn't have a proper UV-A bulb (I just had a UV inspection
lamp)... I could get the chips to superficially erase, but when I
built a rig out of sockets and a trim pot to turn down Vcc to the
EPROM for testing, I could reliably read the former contents at
voltages below 5V even when the chips appeared empty at exactly 5V.
In the end, I gave up on trying to use the lamp I had.  Fortunately I
had a couple of 1MBit FLASH chips and was able to muddle through, but
in the future, I'd probably pack some 27F256s or pack a real EPROM
eraser and use ordinary EPROMs.

-ethan



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