Noise-shaping sense amplifier for MRAM cross-point arrays

• Published in: IEEE journal of solid-state circuits Vol. 41; no. 3; pp. 699 - 704
• Main Authors: Leslie, M.B., Baker, R.J.
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01.03.2006; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Amplifiers; Applied sciences; Arrays; Calibration; Circuit properties; Counting circuits; Current-mode sensing; Detection; Digital filters; Digital modulation; Electric, optical and optoelectronic circuits; Electronic circuits; Electronics; Exact sciences and technology; Integrated circuits; Integrated circuits by function (including memories and processors); Magnetic and optical mass memories; Magnetic modulators; magnetic random access memory (MRAM); magnetic tunnel junction (MTJ); Magnetic tunneling; Magnetoelectric, magnetostrictive, magnetoacoustic, magnetooptic and magnetothermal devices. Spintronics; Magnetoresistive random access memory; Modulators; Noise; Noise reduction; Noise shaping; noise-shaping modulator; Power supplies; self-referenced sensing; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; Sense amplifiers; Storage and reproduction of information; Tunnel junctions; Voltage; voltage-mode sensing; Magnetoresistive device; Memory devices; voltage-mode sensing; Noise reduction; Random access memory; Power supply; Magnetic storage; magnetic random access memory (MRAM); Digital filter; Current mode; Non volatile memory; Complementary MOS technology; Self control; Root mean square value; Voltage mode; magnetic tunnel junction (MTJ); Modulator; Amplifier; self-referenced sensing; noise-shaping modulator; Digital counter; Integrated circuit; Tunnel junction; Signal to noise ratio; Current-mode sensing
• ISSN: 0018-9200; 1558-173X
• DOI: 10.1109/JSSC.2005.864103

A sensing technique using a voltage-mode architecture, noise-shaping modulator, and digital filter (a counter) is presented for use with cross-point MRAM arrays and magnetic tunnel junction memory cells. The presented technique eliminates the need for precision components, the use of calibrations, and reduces the effects of power supply noise. To obviate the effects of cell-to-cell variations in the array, a digital self-referencing scheme using the counter is presented. Measured experimental results in a 180-nm CMOS process indicate an RMS sensing noise of 20 /spl mu/V for a 5-/spl mu/s sense time. Further increases in sense time are shown to increase the signal-to-noise ratio. The current used by the sense amplifier and counter was measured as 10 /spl mu/A when running at 100 MHz or 10 mA when 1000 sense amplifiers are used with a memory subarray having 1000 bitlines.