Time-to-Digital Conversion in Compute-in-Memory Circuits
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Solution Overview
Problem
Current compute-in-memory (CIM) circuits face limitations in scaling and precision due to voltage-based sensing techniques, which lead to increased heat buildup and noise susceptibility as technology is scaled down, affecting the accuracy and efficiency of deep learning operations.
Innovation Solution
Implementing time-to-digital conversion (TDC) circuits within CIM systems, which convert the time it takes for bitline voltages to discharge into digital values, allowing for full-swing operations and improved noise immunity, enabling more precise and scalable computations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If voltage-based sensing techniques are used in CIM circuits, then the circuits can perform computations, but heat buildup increases and noise susceptibility increases as technology is scaled down
Solution Approach 1:
The patent replaces voltage-based sensing with time-based sensing. Instead of measuring voltage levels directly (electrical domain), the circuit measures the time duration of computational results (temporal domain). This substitution eliminates the heat and noise issues associated with voltage sensing while maintaining measurement precision through time-to-digital conversion circuits.
2Adaptability or versatility
If traditional voltage-based sensing is used, then the system can operate, but scalability is limited due to heat and noise issues
Solution Approach 1:
By substituting voltage-based operations with time-based operations, the patent enables scalable CIM circuits. The time-domain computational results can be sensed without the heat accumulation problems that limit voltage-based approaches, allowing the system to scale to larger sizes and higher densities.
3Measurement precision
If high-resolution voltage sensing is implemented to improve precision, then measurement accuracy improves, but energy consumption increases and heat buildup worsens
Solution Approach 1:
The patent substitutes energy-intensive high-resolution voltage sensing with low-power time-based sensing. The time-to-digital conversion process requires significantly less energy than achieving equivalent precision through voltage sensing, as it relies on temporal measurement rather than high-precision electrical analog measurement.
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
TDC circuits enhance the scalability and precision of CIM operations, reducing energy consumption and improving the accuracy of deep learning computations by eliminating the need for high-resolution voltage sensing, thus overcoming the limitations of traditional voltage-based methods.
Implementation Method 1
Implementing time-to-digital conversion (TDC) circuits within CIM systems, which convert the time it takes for bitline voltages to discharge into digital values
Data Source
AI summary
A memory circuit has compute-in-memory (CIM) circuitry that performs computations based on time-to-digital conversion (TDC). The memory circuit includes an array of memory cells addressable with column address and row address. The memory circuit includes CIM sense circuitry to sense a voltage for multiple memory cells triggered together. The CIM sense circuitry including a TDC circuit to convert a time for discharge of the multiple memory cells to a digital value. A processing circuit determines a value of the multiple memory cells based on the digital value.