Adiabatic SRAM with a shared access port using a controlled ground line and step-voltage circuit

An adiabatic 64-kb SRAM circuit with shared reading and writing ports was designed, which enables gradual charging and discharging while maintaining a large VDD so that the problems of V_T variation and electromigration in the nanocircuit can be solved. In the writing mode, the voltage of the memory cell ground line is increased to VDD/2 gradually, and the nMOSFET is turned off so that the memory cell ground line is set in a high-impedance state. Data can then be written easily by decreasing the voltage of one bit line adiabatically, while the voltage of the other bit line remains high. For reading, using the shared reading port, the voltage swing of the global bit-line can be decreased to VDD/4 so that the problems of electromigration can be solved. The reading method enables a gradual current flow in the memory cell. We designed the cell layout and confirmed that the number of transistors in the cell is quasi-six. In addition, two types of new step voltage circuits with tank capacitors are proposed. One is for producing the memory cell ground line voltage and the other for charging the word line voltage adiabatically. Spontaneous step voltage formation is confirmed experimentally.