Two-step Precharge Control for DRAM Bit Line Speed and Oxide Protection
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Solution Overview
Problem
Current memory devices, particularly DRAM, face limitations in precharge time, which affects the overall speed of memory operations due to the risk of gate-oxide breakdown when applying high precharge voltages to precharge transistors.
Innovation Solution
A two-step voltage precharge control method is introduced to gradually increase the precharge voltage, reducing the risk of gate-oxide breakdown by using transistors with thicker gate insulating films and carefully managing the voltage levels to prevent exceeding the gate oxide withstand voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If high precharge voltage is applied to precharge transistors to decrease precharge time, then memory circuit speed is improved, but gate oxide breakdown risk increases
Solution Approach 1:
The precharge operation is divided into two distinct phases: a first precharge phase using a first precharge voltage, and a second precharge phase using a second precharge voltage. This segmentation allows the system to balance between speed and reliability by using different voltage levels at different times, avoiding gate oxide breakdown while still achieving fast precharge when needed.
Solution Approach 2:
The precharge voltage is made dynamic rather than static. The control circuit dynamically switches between the first precharge voltage and the second precharge voltage based on operational requirements. This dynamic adjustment allows the system to optimize performance by applying higher voltage only when necessary and safe, while using lower voltage during normal operation to protect the gate oxide.
2Loss of time
If precharge voltage is increased to improve precharge speed, then precharge time is decreased, but transistor damage risk increases
Solution Approach 1:
The control circuit is configured to apply the first precharge voltage in a preliminary phase before potentially applying the second precharge voltage. This preliminary action prepares the circuit in a safe state first, and only transitions to the higher voltage state when appropriate conditions are met, preventing premature voltage-induced damage while still achieving fast precharge when needed.
Solution Approach 2:
The patent changes the voltage parameter dynamically during precharge operations. By switching between two distinct voltage levels (first precharge voltage and second precharge voltage) based on operational conditions, the system optimizes the balance between precharge speed and transistor safety, reducing precharge time without causing voltage-induced damage.
Data Source
AI summary
Apparatus and methods are disclosed, including an apparatus having a first transistor configured to be coupled to a first bit line, and a control circuit configured to supply a gate of the first transistor with a first voltage to turn on the first transistor, and to supply the gate of the first transistor with a second voltage higher than the first voltage to strengthen a current drive capability of the first transistor.