Joint memory cell to replace DRAM

Joint memory cell to replace DRAM
Richard Ball Hitachi and Cambridge University researchers have designed a memory cell aimed at replacing DRAM, flash and SRAM. Called PLEDM, or phase-state low electron-number drive memory, the memory cell uses two transistors to store a bit. But unlike DRAM it does not lose data when power is removed. “The area is half that of DRAM, is smaller vertically and simpler to manufacture,” said Dr David Williams at the Hitachi Cambridge Labs. PLEDM is also fast – a few tens of nanoseconds per cycle – and, unlike flash, individual bits can be erased. “Because it is non-volatile, we think it takes over from both DRAM and flash,” said Williams. “A lot of people think DRAM will run out of steam in the next ten years.” One main reason for this is that the number of electrons needed to store one bit of data is not decreasing as the memory cell size shrinks. This is because the DRAM cell has no internal amplification and the electrons are needed to retain a sufficiently high signal to noise ratio. Today’s DRAMs typically need half a million electrons per bit, while the PLEDM uses 1,000. This will decrease further as the PLEDM shrinks.


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