Saturday, June 9, 2012

ST 24C02


I want to do a more detailed writeup at some point but here are some quick thoughts.  This 256 byte EEPROM chip was much larger than I was expecting.  Close up of some of the cells:

The charge pump can be seen in the lower right hand corner which is identified by the large capacitors:

 At a quick look what may be the output there appear to be a "high voltage" diode string:

Another interesting thing is that I'd expect a chip this small to be fully custom due to the volume market it targets.  You can see a fair amount of diagonal routing so presumably that's at least somewhat true.  However. one of the markings of a larger chip are standard cells.  Of course, even in a fully custom chip there are some regular patterns for repeated circuits so I'm really only talking about glue logic.  There are a few rows of what look like standard cells (highlighted in red):

However, notice the one highlighted in green has  slightly different width than the ones below it.  Additionally,the left and right bank don't actually have the same width as the right is a little narrower.  So if they did use standard cells and not so much a standard cell layout methodology they must be from several different sized libraries.

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