A Dual-Bit Spin-Based Analog-to-Digital Converter With Double-Check Estimation

This letter presents a three-bit magnetic analog-to-digital converter (MADC) based on the spin Hall effect, which exploits the spin current flowing at both sides of a heavy metal (HM) layer. The shape of the HM can be adjusted to produce multiple switching thresholds. After the input signal is injected, the magnetization of both free layers in the top and bottom magnetic tunnel junctions (MTJs) can be switched simultaneously. The converted results could be quantified by the states of the corresponding MTJs. In order to improve the accuracy and reliability of quantization, a multilayer structure with a double-check estimation method inspired by or gate operation is designed. This dual-bit MADC can reach up to 667 MHz sampling rate with only 0.17 pJ energy consumption, which is well suited for nonvolatile computing based on magnetic devices.