Reprogrammable IP for High Temperature ASICs

Tekmos makes ASICs, which are definitely not programmable. But sometimes, customers need a little bit of programmability in an ASIC. Just look at the increase in FPGAs in modern SOC design. So, we decided to add reprogrammable IP to our high temperature ASIC product offering.

But what type of programmable IP? The high temperature process we use has limits, and one of the main limits is density. So, we decided to start with something small like a PAL. PALs (Programmable Array Logic) have been around for years. They were one of the first programmable devices, and lead the way into the development of FPGAs.

We have one other issue with our technology, and that is it does not support non-volatile memories. Stored charge memories leak away at high temperature. So, we decided to make a RAM based PAL. We chose to make a 22V10 equivalent PAL.

Starting with PALs has several advantages. First, the schematic is known, which simplifies the reverse engineering. Most of the work involves replacing the fuse array with a RAM. One interesting engineering point was the design of the wired-AND gate that the fuses are attached to. Most PALS used a pull-up resistor, and allowed the inputs to pull it low. This has the simplest layout, but continuously draws high current. And we were concerned that the increased leakages experienced at high temperature would cause this architecture to fail. So, we instead opted to build a discrete, 44-input AND gate. The layout is more complicated, but it has superior performance.

Another advantage of copying existing PALs is that the programming instructions are a JEDEC standard. If we maintain fuse compatibility, there are a number of existing software programs that can be used to develop circuits. And most of these programs are available at no cost. In some cases, the source code is also available.

Interfacing IP to the rest of the design is always an important issue. Our IP is designed to appear as a RAM to the rest of the ASIC. So, the interface becomes just a DMA into that RAM. We can set the data bus width to 8, 16, or 32 bits in size. Internally, the RAM is organized as 133 words of 44 bits.

Call us and find out how you can add reprogrammability to your next high temperature ASIC. Contact Tekmos Sales

Date

2017-12-11