UTXQ512 Datasheet PDF

Aeroflex UTMC Application Note UTXQ512-AN-000 _______________________________________________ CONVERTING AEROFLEX UTMC UT9Q512 4M SRAM into an SEU IMMUNE 1M X 1 SRAM This application note describes how to use two UT9Q512 4M SRAMs and one UT54ACS151 logic device to mimic a 1Mx1 SRAM. As shown below, the single bit is written into three locations of the same. When the data is read out, it is used in a voting system to select either a 0 or a 1 output. This voting method virtually makes it immune to SEU hits. Since the bits of a word are not physically adjacent on the die, it is nearly impossible for one particle to cause two bits to flip in the same word. As such, it would require multiple particle hits to cause an upset. The system timing results in maximum read cycle of 48ns, (25ns SRAM read + 23ns input to Y). For better system performance Aeroflex UTMC can screen for memories with read cycles access times down to 17 ns. The timing analysis above assumes capacitive output loads of 50 pF or less.