LOW-VOLTAGE FAST-WRITE NVSRAM CELL

摘要

This invention discloses several embodiments of a low-voltage fast-write NVSRAM cells, made of either of a 2-poly floating-gate type flash cell or a 1-poly charge-trapping SONOS or MONOS flash cell with improvement by adding a Bridge circuit. This Bridge circuit is preferably inserted between each LV 6T SRAM cell and each HV Flash cell that comprises one paired complementary Flash strings. The Flash strings can be made of either 2T or 3T Flash strings. The tradeoff of using either a 2T or a 3T Flash string is subject to the gate area penalty and required design specs. One improvement for adding the Bridge circuit into the NVSRAM cell is to ensure the data writing between Flash cell and SRAM cell with the same polarity and to allow the operation down to low 1.2V Vdd.