Temperature-Compensated Precharge Control Signal Generator for Flash Memory
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Solution Overview
Problem
Conventional precharge control methods in flash memory devices face challenges in accurately reading data at high temperatures due to increased bit line leakage current, leading to Off cell failures and reduced read rates, as the precharge time is compromised by variations in cell characteristics and manufacturing processes.
Innovation Solution
A precharge control signal generator that adjusts precharge time based on operating temperature using a proportional to absolute temperature (PTAT) current or voltage, generating a precharge control signal to optimize precharge duration and mitigate bit line leakage current issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the precharge time is lengthened to meet desired Off cell detection characteristics, then the Off cell detection accuracy is improved, but the read rate decreases due to unnecessary precharge time
Solution Approach 1:
The precharge time is made dynamic by generating a temperature-dependent precharge control signal that adjusts the precharge duration based on operating temperature. At high temperatures where bit line leakage current increases, the precharge time is automatically extended to ensure accurate Off cell detection. At low temperatures where leakage is minimal, the precharge time is reduced to avoid unnecessary delays and maintain high read rates. This dynamic adjustment resolves the contradiction by adapting the precharge time to actual operating conditions rather than using a fixed conservative value.
2Reliability
If the precharge time is lengthened to account for degraded bit line precharge characteristic at specific locations, then the precharge reliability is improved, but the read rate is compromised
Solution Approach 1:
The patent applies local quality by providing temperature-compensated precharge control that addresses degradation at specific locations (high-temperature operating conditions) without affecting performance at other conditions. The temperature-dependent precharge control signal selectively extends precharge time only when and where it is needed (at high temperatures causing degradation), while maintaining optimal shorter precharge times at normal operating conditions, thus preserving read rate for the majority of operating scenarios.
3Measurement precision
If the precharge time is increased to prevent Off cell failure at high temperature, then the detection accuracy is improved, but unnecessary precharge time is incurred at lower temperatures
Solution Approach 1:
The patent changes the precharge time parameter dynamically based on temperature conditions. A temperature-dependent precharge control signal is generated that modifies the precharge duration according to the operating temperature. At high temperatures where bit line leakage current causes Off cell failures, the precharge time is automatically increased to ensure accurate detection. At lower temperatures where leakage is minimal, the precharge time is reduced to eliminate unnecessary delays. This parameter change based on operating conditions resolves the contradiction between detection accuracy and time loss.
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 solution effectively increases precharge time at higher temperatures to prevent Off cell failures and decrease precharge time at lower temperatures, enhancing data read accuracy and rate while minimizing unnecessary precharge time, thus improving product reliability and read performance.
Implementation Method 1
a proportional to absolute temperature (PTAT) current generating circuit which generates a PTAT current
Data Source
AI summary
A precharge control signal generator and a semiconductor memory device include a precharge control signal generating circuit which generates a precharge control signal and applies the precharge control signal to a sensing circuit, and a sensing circuit configured to precharge a bit line connected to a memory cell according to the precharge control signal and read data stored in the memory cell. The precharge control signal controls the sensing circuit so that a precharge time is adjusted according to operating temperature.