DRAM Initialization Refresh for Stable Bit Line Sensing
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Solution Overview
Problem
During the initialization of dynamic random access memory, the charge amount in memory cells is not fixed due to coupling and static electricity, leading to unstable voltage states on bit lines, which results in slow sensing speed and high power consumption, with a risk of sensing failure.
Innovation Solution
A semiconductor memory device with an initialization method that includes an equalize circuit, refresh controller, and initialization controller to stabilize charge amounts in memory cells through periodic auto-refresh commands, using equalize and sense control voltages to enable equalize circuits and disable sense amplifiers during initialization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If no turn on voltage is applied to the word line during initialization, then the access transistor remains in an off state to maintain memory cell integrity, but the charge amount in each memory cell becomes unstable due to coupling and static electricity effects
Solution Approach 1:
The patent applies preliminary action by performing refresh operations on memory cells during the initialization period before normal operations begin. The refresh controller continuously refreshes memory cells during initialization, stabilizing their charge amounts before the access transistors are turned on for normal sensing operations. This preliminary stabilization prevents charge instability issues that would otherwise occur during initialization.
2Speed
If the memory cell charge amount is unstable during initialization, then the voltage on the bit line cannot enter a stable state quickly, resulting in slow sensing speed and higher power consumption
Solution Approach 1:
The refresh controller performs preliminary refresh operations during initialization to stabilize memory cell charges before normal sensing operations. This preliminary stabilization ensures that when sensing operations begin, the bit line voltages can quickly reach stable states, achieving fast sensing speed and low power consumption from the start of normal operations.
3Reliability
If the memory cell charge amount is unstable during initialization, then there is a chance of sensing failure
Solution Approach 1:
The refresh controller continuously refreshes memory cells during the initialization period, performing preliminary stabilization of charge amounts before normal sensing operations begin. This eliminates the charge instability that would otherwise cause sensing failures, ensuring high sensing reliability from the start of normal operations.
Data Source
AI summary
A semiconductor memory device and an initialization method thereof are provided. The semiconductor memory device includes a memory array, a refresh controller, and an initialization controller. The memory array has a plurality of equalize circuits and N memory cells. The equalize circuits are respectively coupled to the N memory cells via a plurality of bit line pairs. The refresh controller is configured to refresh initial data in sequence to the N memory cells according to an auto-refresh command. The initialization controller is configured to perform an initialization operation according to an initialization activation command. The initialization controller enables the equalize circuits and periodically generates the auto-refresh command during the initialization operation.