27C256/27C512 SOIC.TSOP EEPROMS QUESTION

[mikeb]

HELLO ONCE MORE AND AGAIN THIS TIME MY REQUEST IS A SIMPLE ONE, IM LOOKIN FOR SOME INFO ON SOIC OR TSOP 27C256 OR 27C512 EEPROMS. ACTUALLY I HAVE DATA BUT ALL THE IC'S IM FINDING ARE OTP TYPES, I TRYING TO FIND OUT IF THE SOIC OR TSOP, 27C256 OR 27C512 EEPROMS ARE EVEN MADE TO BE ERASED AND REPORGRAMMED, IF SO IF ANY ONE KNOWS OF A GOOD WEBSITE OR SOURCE TO GET EM AND CAN PASS IT ON ID REALLY APPRECIATE THE INFO.

[rshayes]

The 27Cxxx series parts are not EEPROMS. They are EPROMS. An EEPROM is an electrically erasable, programmable read only memory. An EPROM is an erasable, programmable read only memory. An EEPROM can be erased electrically, an EPROM is erased with ultraviolet light.<p>Erasable EPROMs are packaged in ceramic packages with a quartz window to allow ultraviolet light to reach the chip. One-Time-Programmable devices are the same chips packaged in plastic. Once programmed, they can't be erased, since the plastic is opaque to ultraviolet light. Most surface mount packages are plastic. There might be a few devices packaged in ceramic packages with quartz windows, but these may be hard to find.<p>Atmel (www.atmel.com) lists a series of parts with AT28Cxxx part numbers. These may be what you are looking for, since they are described as EEPROMs.

[Chris Foley]

The parts you're looking for (27C256, 27C512) are available in ceramic DIP, plastic DIP, SOIC, TSOP, and PLCC packages. However, the erasure window is only available in the CERDIP package, as far as I can tell. These EPROMS are called OTP, for one-time programmable. Somewhere along the line long ago, the manufacturers discovered that only a very small percentage of EPROMS were actually getting pulled from circuits, erased, and reprogrammed. So, by losing the window, they made it so you could program them, but not erase them, and save some bucks (the molding process for the other IC packages is not conducive to a large open space for the chip as well as the lens on top). Sorry, but I think you're out of luck finding the other packages with the erasure lens.<p>By the way, are you intending to put the whole board in the EPROM eraser? 8-o