A NAND-SPIN-Based Magnetic ADC

This brief introduces a 3-bit magnetic analog-to-digital converter (MADC) employing the NAND-SPIN based multi-bit device which has the same structure as the NAND-SPIN memory cell. By adjusting the physical shape of the heavy metal (HM) line, the all-in-one integrated NAND-SPIN device exhibits multiple switching thresholds which could quantify the input current into several states and store them into the corresponding Magnetic Tunnel Junctions (MTJs). In order to read data reliably, a read port is connected to each Spin Orbit Torque (SOT) MTJs so as to minimize Tunnel Magnetoresistance (TMR) degradation due to non-uniform heavy metal resistance. In addition, an HM size adjustment methodology is proposed to improve the conversion accuracy and switching reliability. Detailed micromagnetic simulation results show that the proposed MADC could achieve 5 GHz sampling rate with only 0.068∼pJ conversion energy, and in-memory conversion for higher bit resolution while provides the benefit of nonvolatility.