Depletion-Type Voltage Drivers for Low-Energy Memory Polarity Transitions

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Solution Overview

Problem

Voltage drivers for memory cells experience high energy consumption during polarity transitions, particularly in cross-point memory systems where phase-change memory devices are absent, leading to inefficiencies in programming and reading operations.

Innovation Solution

The implementation of depletion-type voltage drivers that reduce energy consumption by minimizing voltage swings during polarity transitions, using configurations where voltage drivers apply selection and de-selection voltages of opposite polarities, thereby reducing energy expenditure.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If inverter-type voltage drivers are used to drive polarity transitions in memory cells, then the memory operations can be performed, but energy consumption becomes excessively high (over 120 pJ per transition)

Engineering Contradiction:

Improveenergy consumption during polarity transitionVSAvoidmemory operation efficiency

Core Design Contradiction:

Use of energy by moving objectVSEase of operation

Solution Approach 1:

The patent changes the operating parameters of the voltage driver by transitioning from inverter-type to depletion-type transistor operation. This parameter change reduces the voltage swing required during polarity transitions, thereby reducing energy consumption from over 120 pJ to about 2-3 pJ per transition while maintaining memory operation functionality.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent inverts the conventional approach by using depletion-type transistors instead of the standard inverter-type logic. This inversion allows the voltage driver to operate with reduced voltage swings during polarity transitions, achieving significant energy savings while maintaining the required memory cell driving capability.

Inventive Principle:

Principle #13The other way round (Inversion)

2Reliability

If voltage drivers apply full voltage swings during polarity transitions, then memory cells can be properly programmed and read, but power consumption increases significantly

Engineering Contradiction:

Improvememory cell programming and reading accuracyVSAvoidpower consumption during polarity transition

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The patent modifies the voltage driver parameters by using depletion-type transistors that require smaller voltage swings to achieve the same memory cell state transitions. This parameter change maintains reliable programming and reading operations while reducing power consumption by minimizing unnecessary energy dissipation during voltage transitions.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS11527286B2Voltage drivers with reduced power consumption during polarity transition

Publication Date: 2022.12.13 MICRON TECHNOLOGY INC

AI summary

An integrated circuit memory device having: a memory cell; and a voltage driver of depletion type connected to the memory cell. In a first polarity, the voltage driver is powered by a negative voltage relative to ground to drive a negative selection voltage or a first de-selection voltage; In a second polarity, the voltage driver is powered by a positive voltage relative to ground to drive a positive selection voltage or a second de-selection voltage. The voltage driver is configured to transition between the first polarity and the second polarity. During the transition, the voltage driver is configured to have a control voltage swing for outputting de-selection voltages smaller than a control voltage swing for output selection voltages.