Capacitor Mesh Compute-in-Memory for Low-Latency MAC

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Solution Overview

Problem

Data movement between processor and memory in traditional computing systems presents a significant performance and energy bottleneck, particularly in applications like machine learning, due to the separation of data storage and computational tasks.

Innovation Solution

An apparatus comprising a capacitor mesh circuit and a bitcell array, where each bitcell stores a weight bit and multiplies it by an input bit, with the output coupled to a capacitor mesh forming a binary-weighted capacitive voltage divider, enabling partial multiply-accumulate operations and accumulating results in a sample-and-hold circuit for analog-to-digital conversion.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If data is stored in separate memory and processed by a separate processor, then data storage and computational tasks are clearly separated, but data movement between processor and memory becomes a significant performance and energy bottleneck

Engineering Contradiction:
Improveseparation of storage and computationVSAvoidprocessing performance
Core Design Contradiction:
Device complexityVSProductivity

Solution Approach 1:

The patent merges memory storage and computational processing into a single integrated structure. Bitcells that traditionally only store data are enhanced with multiplication units that can perform arithmetic operations directly within the memory array, eliminating the need to move data between separate memory and processor components.

Inventive Principle:
Principle #5Merging (Combining)

Solution Approach 2:

The bitcell structure is designed to serve multiple functions: it can store weight bits in its storage unit and simultaneously perform multiplication operations with input bits through its multiplication unit. This multi-functional design allows the same hardware structure to handle both data storage and data processing tasks.

Inventive Principle:
Principle #6Universality (Multi-functionality)

2Device complexity

If data is stored in separate memory and processed by a separate processor, then functional separation is maintained, but energy consumption increases due to data movement

Engineering Contradiction:
Improvefunctional separationVSAvoidenergy consumption
Core Design Contradiction:
Device complexityVSUse of energy by moving object

Solution Approach 1:

The patent merges memory storage and computational processing into a single integrated structure. Bitcells that traditionally only store data are enhanced with multiplication units that can perform arithmetic operations directly within the memory array, eliminating the need to move data between separate memory and processor components.

Inventive Principle:
Principle #5Merging (Combining)

3Ease of manufacture

If traditional separate memory and processor architecture is used, then modular design is simplified, but computational latency increases

Engineering Contradiction:
Improvemodular designVSAvoidcomputational latency
Core Design Contradiction:
Ease of manufactureVSLoss of time

Solution Approach 1:

The patent merges memory storage and computational processing into a single integrated structure. Bitcells that traditionally only store data are enhanced with multiplication units that can perform arithmetic operations directly within the memory array, eliminating the need to move data between separate memory and processor components.

Inventive Principle:
Principle #5Merging (Combining)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This approach reduces computational latency and energy consumption by performing arithmetic operations directly in memory, enhancing processing performance and efficiency in tasks like convolutional functions and machine learning algorithms.

Implementation Method 1

each signal line in the plurality of signal lines is electrically coupled such that the capacitor mesh circuit forms a binary-weighted capacitive voltage divider circuit between the plurality of signal lines

Methodology Applied
Scientific EffectCapacitive voltage division: Capacitance

Implementation Method 2

the output of each bitcell in a column of the bitcell array is coupled to corresponding signal line in the capacitor mesh circuit via at least one capacitor

Methodology Applied
Scientific EffectElectrical charge storage: Capacitance

Data Source

PatentEP4589478A1Compute-in-memory apparatus
Publication Date: 2025.07.23 NOKIA SOLUTIONS & NETWORKS OY
  • EP4589478A1 patent drawingFigure 1
  • EP4589478A1 patent drawingFigure 2A~2B
  • EP4589478A1 patent drawingFigure 3A

AI summary

According to an example embodiment, an apparatus comprises a capacitor mesh circuit comprising a plurality of signal lines and a bitcell array comprising a plurality of bitcells.