Patent Number: 8,879,344

Title: Phase change memory with flexible time-based cell decoding

Abstract: Methods and systems for time-based cell decoding for PCM memory. Generally, the higher the PCM element resistance, the longer it takes for a read output to change state. PCM memory output is determined using differentiated timings of read outputs changing state, rather than differentiated values of read outputs. In some single-bit single-ended sensing embodiments, a reference, with resistance between the resistances corresponding to a pair of adjacent logical states, is stored in multiple reference cells; a "vote" unit emits a clock signal when a majority of the reference cell read outputs transition at the vote unit. Timing units produce different binary outputs depending on whether a data read output or the clock signal changes state first at the timing unit. Time-based decoding provides advantages including improved temperature and drift resilience, improved state discrimination, improved reliability of multibit PCM, and fast and reliable sensing.

Inventors: Willey; Aaron D. (Burlington, VT), Jurasek; Ryan (Burlington, VT)


International Classification: G11C 7/00 (20060101)

Expiration Date: 2019-11-04 0:00:00