US 6,661,708 B2 · Non-volatile memory with improved sensing and method therefor

Abstract

Floating gate memories such as EEPROM and flash EEPROM have the memory state of a memory cell thereof determined by sensing the conduction current of the cell. Inherent noise fluctuations in the conduction current during sensing are canceled out by averaging the sensing over a predetermined period of time. In one embodiment, as an integral part of the averaging process, the averaged conduction current is obtained directly as a digital memory state. Accuracy in sensing is therefore greatly improved by avoiding sensing noise with the current and avoiding having to resolve its memory state in the analog domain by comparison with another noisy reference current. In another embodiment, conventional sensing techniques are improved when sensing is made by comparison with a reference current by means of a symmetric, switched or non-switched capacitor differential amplifier.

Claims19

Dependent claims

In a non-volatile memory comprising an array of memory cells, each memory cell having a source, a drain, a charge storage and a control gate, said charge storage receptive to variable amount of charges being stored therein for designating one of a plurality of memory states, a method of sensing a group of memory cells in parallel, comprising:

applying predetermined voltages respectively to the source, the drain and the control gate of individual memory cells of said group in parallel, thereby producing a source-drain current relative to the amount of charges stored in the charge storage of each memory cell in the group, said source-drain current having an inherent noise fluctuation component;
and
obtaining an average value of said source-drain current over a predetermined period of sensing time sufficient for the noise fluctuation component therein to cancel to a predetermined level;
and
determining whether said average value of said source drain current is higher or lower than a predetermined value for each memory cell of the group.

2 more elements

A non-volatile memory comprising an array of memory cells, each memory cell having a source, a drain, a charge storage and a control gate, said charge storage receptive to variable amount of charges being stored therein for designating one of a plurality of memory states, said non-volatile memory further comprising:

means for applying predetermined voltages respectively to the source, the drain and the control gate of individual memory cells of a group of memory cells being sensed in parallel, thereby producing a source-drain current relative to the amount of charges stored in the charge storage of each memory cell in the group, said source-drain current having an inherent noise fluctuation component;
and
means for obtaining an average value of said source-drain current over a predetermined period of sensing time sufficient for the noise fluctuation component therein to cancel to a predetermined level for each memory cell of the group;
means for determining whether said average value of said source drain current is higher or lower than a predetermined value.

1 more element

Dependencies are inferred from the claim text.

Non-volatile memory with improved sensing and method therefor

Life of this patent

Non-volatile memory with improved sensing and method therefor

Life of this patent

Abstract

Claims19