A 14.7Mb/mm2 28nm FDSOI STT-MRAM with Current Starved Read Path, 52Ω/Sigma Offset Voltage Sense Amplifier and Fully Trimmable CTAT Reference

摘要

In this paper we present a read circuitry that tackles all STT-MRAM read challenges. First, a negative temperature coefficient (NTC) reference based on an MTJ in series with an “NTC” resistor circuit emulator is described. Then, an offset cancelled voltage sense amplifier using low read current and reference averaging is discussed. Measurement results show a maximum of 2% reference impedance error (vs. ideal) and 1.7% read error rate degradation (vs. technology intrinsic defectivity rate). A 14.7Mb/mm² memory density is also achieved, which is the best STT-MRAM published density for embedded applications.