Lynn Reed at Hi-Tec 2014

Last month, Tekmos presented a paper at the  HiTec conference. HiTec is dedicated to high temperature electronics, ranging from the relatively cool 175C up to the 1200C range for Silicon Carbide.  It also covers high temperature materials and passive components.

The Tekmos paper investigated the use of refresh cycles to assist with data retention in EEPROMS.  We are developing a new 256K, high temperature, and high reliability EEPROM.  At elevated temperatures, the charge stored in the memory leaks away, and must be replenished.  While an EEPROM at 85C can be expected to hold the data for 10 years, at higher temperatures (~200C), the data retention time is measured in days.  Restoring the data is made more complicated since the number of times that an Erase-Write cycle can be used also decreases with temperature.  The 100,000 cycles guaranteed at lower temperatures becomes 100s of cycles at high temperature.

We get around this by using a refresh cycle.  A refresh cycle does not do an erase prior to the write, and so can only be used to re-write the same data.  We were concerned that repeated refresh cycles could also cause damage, but our experiments showed that a refresh cycle is safe.

To prove this, we set up a system using our TK68HC11E1 devices, which contain 512 bytes of EEPROM.  This is the same basic EEPROM cell that we will use in our 256K EEPROM.  We attached 77 of the microcontrollers to a board, and configured them so that we could communicate with a specific microcontroller.  Then we downloaded programs into the microcontrollers, and ran experiments.  The experiments included such things as determining the number of Erase-Write cycles it took to burn out an oxide, or just giving the part a fixed number of refresh cycles.  This made it easy to collect a large amount of high quality data that was the basis of our paper.

For the first time, Tekmos had an exhibit at HiTec.  We showed our TK68HC811E2 high temperature microcontroller, and our 250C ASICs.  We also provided a preview of our 256K EEPROM, our 250C TK80H51 microcontroller, and theTKH4003 FPGA.  These last three products are under development, and we will be introducing them over the next year.

One advantage of exhibiting at a conference is that it provides feedback about what customers really want to see in products.  It also shows what the competition is doing.  Together, that provides invaluable marketing guidance for our own efforts.

The conference is small, with about 300 attendees.  Still, this was one of the best shows that we have ever exhibited at.  The crowd what highly focused, and almost every booth conversation was of high quality.  We have been to shows that were 30 times larger, and gone away with a fraction of the leads we got from HiTec.

We will definitely be exhibiting at the HiTen conference next year in England.

The Effects of Repeated Refresh Cycles on the Oxide Integrity of EEPROM Memories at High Temperature 

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