Sense amplifier for Stpin-Torque Transfer Magnetic Random Access Memory (STT-MRAM) using Bit-line feedback

초록

Conventional reference sense scheme for Spin-Torque Transfer Magnetic Random Access Memory (STT-MRAM) always set a reference resistor for sensing bit state. It is hard to get a suitable resistance value because of the resistance distribution where RAP has a large range than RP. To set a reference resistor with the middle value between RAP and RP, it always need at least 2 MTJ with AP and P state, respectively, and the current through the reference resistors houldbe twice of MRAM cell. This will result waste of chip area and power consumption. In this paper, to solve these problems, we proposed a method and circuit that set a fixed reference voltage value (e.g.Vhalf=VDD/2) instead of a reference resistor. A read current is supplied through the MRAM cell to get a bit-line voltage comparing with the reference voltage for sensing. And the current varies following the bit-line voltage using bit-line feedback.