Adaptive Precharge Current Sensing Circuit for Nonvolatile Memory
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Solution Overview
Problem
NAND flash memory devices face challenges in maintaining accurate data retention at high temperatures due to increased leakage currents, which can cause on-cells to be mistaken for off-cells, reducing the sense margin and affecting the reliability and performance of nonvolatile memory devices.
Innovation Solution
A sensing circuit with a precharge current generator, an adjusting transistor, and an adaptive control voltage generator is implemented, which adjusts the precharge current based on temperature to compensate for leakage currents, ensuring sufficient precharging at high temperatures and preventing over-precharging at low temperatures, thereby enhancing the sense margin.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the process is refined and operation voltage is lowered, then power consumption is reduced, but leakage currents of bit line increase at high temperature
Solution Approach 1:
The patent changes the precharge current parameter dynamically based on temperature conditions. The precharge current is increased at high temperatures to compensate for increased leakage currents, while being reduced at low temperatures to maintain low power consumption. This parameter adaptation resolves the contradiction between power efficiency and leakage current management.
2Reliability
If precharge current is increased to compensate for leakage currents, then sense margin is improved, but power consumption increases
Solution Approach 1:
The patent implements dynamic adjustment of precharge current based on temperature conditions. The precharge current generator receives temperature information and dynamically changes the precharge current level accordingly. This dynamic approach ensures sufficient sense margin at high temperatures while minimizing power consumption at low temperatures, resolving the contradiction between reliability and power usage.
3Measurement precision
If precharge current is increased at high temperature, then data retention accuracy is improved, but device complexity increases
Solution Approach 1:
The patent applies preliminary action by pre-charging the bit line to a higher voltage level before the read operation when high temperature is detected. This preliminary precharge compensates for the expected leakage currents that will occur during the operation, ensuring accurate data retention detection without requiring complex real-time compensation circuits.
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 compensates for temperature-induced leakage currents, improving the reliability and performance of nonvolatile memory devices by maintaining accurate data retention and increasing read speed.
Implementation Method 1
The adaptive control voltage generator generates a control current which is proportional to an operating temperature of the nonvolatile memory device, in response to the precharge signal and a second control voltage and boosts a level of the first control voltage in proportion to the operating temperature, based on the control current
Data Source
AI summary
A sensing circuit of nonvolatile memory device includes a precharge current generator, an adjusting transistor, and an adaptive control voltage generator. The precharge current generator connected to a sensing node and generates a precharge current provided to a bit-line of the nonvolatile memory device, in response to a precharge signal. The adjusting transistor, connected between the sensing node and a first node, adjusts an amount of the precharge current provided to the bit-line in response to a first control voltage. The adaptive control voltage generator generates a control current proportional to an operating temperature, in response to the precharge signal and a second control voltage and boosts a level of the first control voltage in proportion to the operating temperature. The second control voltage is inversely proportional to the operating temperature.