Memory Read Sensing Capacitor Calibration for Charge Coupling
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Solution Overview
Problem
Non-volatile memories with an All Bit Line (ABL) architecture are susceptible to incorrect reads due to charge coupling between bit lines, especially for long bit lines, leading to misreads when the induced charge exceeds the minimum switching charge threshold.
Innovation Solution
A calibration circuit determines a target sensing capacitance based on a calibration cell or cells, adjusting the sensing capacitance value to minimize the impact of coupled charges during read operations, ensuring accurate state detection by integrating a configurable sensing capacitance in the sensing circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a fixed sensing capacitance value is used in the sensing circuit, then the circuit design is simple, but read accuracy deteriorates due to charge coupling from adjacent bit lines
Solution Approach 1:
The sensing capacitance value is made dynamically adjustable through a calibration circuit that determines the optimal capacitance value based on actual switching charge characteristics. The calibration circuit measures the switching charge from a calibration cell and uses this information to set an appropriate sensing capacitance value, allowing the system to adapt to variations in charge coupling effects without requiring complex fixed circuit designs.
Solution Approach 2:
The invention changes the sensing capacitance parameter based on measured switching charge characteristics. By calibrating the sensing capacitance value to match the actual charge conditions in the memory array, the system optimizes read accuracy while maintaining a relatively simple circuit architecture. The calibration process establishes an appropriate capacitance value that compensates for charge coupling effects.
2Measurement precision
If the sensing capacitance is increased to reduce the impact of coupled charges, then read accuracy improves, but the minimum detectable switching charge decreases
Solution Approach 1:
The calibration circuit provides feedback by measuring the switching charge from a calibration cell and using this information to determine the optimal sensing capacitance value. This feedback mechanism allows the system to automatically adjust the sensing capacitance to an appropriate level that improves read accuracy without excessively reducing the minimum detectable charge threshold, as the adjustment is based on actual measured conditions rather than fixed increases.
3Measurement precision
If a calibration circuit is implemented to determine optimal sensing capacitance, then read accuracy improves, but device complexity and calibration time increase
Solution Approach 1:
The calibration circuit performs preliminary measurement and determination of the optimal sensing capacitance value before actual memory read operations. By establishing the appropriate capacitance value in advance based on calibration cell characteristics, the system enables accurate reads without requiring repeated calibration during operation, thus limiting time loss to a single calibration phase.
4Measurement precision
If the sensing capacitance is adjusted for each memory cell, then read accuracy improves, but the complexity of the sensing circuit increases
Solution Approach 1:
The calibration circuit serves multiple functions: it measures switching charge characteristics, determines the optimal sensing capacitance value, and provides calibration data for the sensing circuit. This multi-functional approach allows the system to achieve cell-specific optimization without requiring separate complex circuitry for each memory cell, as the calibration circuit provides universal calibration information that can be applied across the memory array.
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
The calibration circuit reduces the likelihood of misreads by adapting the sensing capacitance to the specific switching charge characteristics of individual memory cells, improving read accuracy by minimizing the effect of induced charges from adjacent bit lines.
Implementation Method 1
integrating a configurable sensing capacitance in the sensing circuit
Data Source
AI summary
Disclosed herein are devices, methods, and systems for calibrating a sensing capacitance value used by a sensing circuit when reading memory cells of a memory. The calibration circuit includes a calibration cell associated with a predefined programming state of the calibration cell. The calibration circuit also includes a read circuit configured to perform a read operation on the calibration cell that generates a calibration voltage based on the predefined programming state and convert the calibration voltage to a target capacitance value based on the calibration voltage. The read circuit is configured to provide the target capacitance value to the memory as the sensing capacitance for the sensing circuit to use when reading the memory cells of the memory.