Memory Array Bit-Line Conversion for Linear Low-Power IMC

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Solution Overview

Problem

Existing in-memory computing chips face challenges with non-linear and energy-hungry analog-to-digital converting operations, necessitating innovative designs for low power consumption and high linearity.

Innovation Solution

The proposed solution involves an in-memory computing apparatus with a memory array structure that includes complementary bit lines and a comparator to generate average voltages, performing incremental steps to determine digital codes through controlled switch operations, enhancing linearity and reducing power consumption using one-step or binary-search incremental methods.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If existing analog-to-digital converting operation is used in in-memory computing chips, then the converting function is achieved, but the operation is non-linear and energy hungry

Engineering Contradiction:
Improvelinearity of converting operationVSAvoidpower consumption of converting operation
Core Design Contradiction:
Measurement precisionVSUse of energy by moving object

Solution Approach 1:

The patent replaces the traditional mechanical/electronic analog-to-digital converter with a neural network-based computational system. The neural network processes analog signals from the memory array directly through software algorithms, eliminating the need for hardware ADC circuits. This substitution achieves linear converting characteristics through controlled incremental operations while significantly reducing power consumption by performing computations in the digital domain rather than requiring energy-intensive analog circuitry.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

2Measurement precision

If higher linearity is achieved in analog-to-digital converting, then measurement precision is improved, but power consumption increases

Engineering Contradiction:
Improvelinearity of digital outputVSAvoidpower consumption of converting circuit
Core Design Contradiction:
Measurement precisionVSUse of energy by stationary object

Solution Approach 1:

The patent segments the analog-to-digital conversion process into multiple incremental steps, where the analog signal is converted through a series of smaller voltage steps rather than a single large conversion. Each step involves comparing the analog voltage with a reference voltage and adjusting incrementally. This segmentation achieves high linearity by breaking down the non-linear conversion into linear incremental operations, while the energy consumption is distributed across multiple low-power comparison operations rather than requiring a high-power single-step converter.

Inventive Principle:
Principle #1Segmentation

3Adaptability or versatility

If traditional analog-to-digital converter is used, then converting function is provided, but device complexity and energy consumption are high

Engineering Contradiction:
Improveconverting function capabilityVSAvoidcomplexity of converting circuit
Core Design Contradiction:
Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent implements a universal computing platform where the memory array serves multiple functions: it acts as both the data storage medium and the computational element for analog-to-digital conversion. The same memory structure that stores data is used to perform the converting operation through controlled voltage adjustments and comparisons. This eliminates the need for separate, complex ADC circuitry, reducing device complexity while maintaining full converting functionality through the multi-functional memory array system.

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

Data Source

PatentUS10692549B1Memory array structure, in-memory computing apparatus and method thereof
Publication Date: 2020.06.23 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD
  • US10692549B1 patent drawing
  • US10692549B1 patent drawing
  • US10692549B1 patent drawing

AI summary

A memory array structure that includes memory columns having first bit lines and second bit lines is introduced. Each of the memory columns includes a bit line pair, a pre-charge switch pair and a first switch pair. Output voltages from the first bit lines and the second bit lines are used to generated a first average voltage and a second average voltage, respectively. One of the first average voltage and the second average voltage is a lower average voltage and another one of the first average voltage and the second average voltage is a higher average voltage. The pre-charge switch pair and the first switch pair of a selected memory column among the plurality of memory columns are controlled to repeatedly perform an incremental step to increment the lower average voltage by a step voltage until the lower average voltage is greater than the higher average voltage.