Adaptive reference scheme for magnetic memory applications

摘要

A structure and method is described for an adaptive reference used in reading magnetic tunneling memory cells. A collection of magnetic tunneling memory cells are used to form a reference circuit and are coupled in parallel between circuit ground and a reference input to a sense amplifier. Each of the magnetic memory cells used to form the reference circuit are programmed to a magnetic parallel state or a magnetic anti-parallel state, wherein each different state produces a different resistance. By varying the number of parallel states in comparison to the anti-parallel states, where each of the two states produce a different resistance, the value of the reference circuit resistance can be adjusted to adapt to the resistance characteristics of a magnetic memory data cell to produce a more reliable read of the data programmed into the magnetic memory data cell.

主权项

1. An adaptive reference circuit for reading a magnetic memory cell, comprising:
a) a magnetic memory cell connected to a data input of a sense amplifier; b) a reference circuit formed by a plurality of pairs of magnetic memory cells, numbering at least four memory cells, and coupled in parallel to a reference input of the sense amplifier, wherein an impedance value of the plurality of pairs of magnetic memory cells averaged together to provide an adaptive reference signal for reference input to the sense amplifier; c) each of the magnetic memory cells of said reference circuit programmed to adjust an average value of the reference circuit, wherein the adaptive reference signal formed from memory cells designated as reference cells and individually programmed to adjust to variations in a separation between parallel and anti-parallel states of memory cells; and d) said reference circuit programmed to optimize read performance of the magnetic memory cell and to correct for a change in temperature dependence in the reference circuit.