RC Delay Circuit Reset Precharge for NBTI-Stable Timing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Semiconductor devices with RC delay circuits are vulnerable to negative bias temperature instability (NBTI) stress degradation, which affects the PMOS threshold voltage and drain current, leading to timing instability in control signals.
Innovation Solution
Incorporating a reset signal function into the RC delay circuit, specifically using a NAND gate with a reset function to precharge nodes to a voltage level during stand-by mode, reducing NBTI stress degradation by resetting each node to a high voltage level responsive to the reset signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If RC delay circuits are used to introduce delay into control signals, then timing adjustment capability is improved, but vulnerability to NBTI stress degradation increases
Solution Approach 1:
The patent applies preliminary action by precharging the output node of the RC delay circuit to a high voltage level using a precharge transistor before the normal delay operation begins. This precharging action prepares the circuit in advance to avoid the harmful low-voltage state that causes NBTI degradation, while still maintaining the required delay functionality through the RC time constant.
2Device complexity
If PMOS threshold voltage is allowed to fluctuate according to NBTI stress degradation, then device operation is simpler, but output timing stability deteriorates
Solution Approach 1:
The patent implements beforehand cushioning by introducing a precharge transistor that actively compensates for the threshold voltage fluctuations caused by NBTI stress. This transistor provides a cushioning effect by maintaining the output node at a high voltage level, thereby protecting the output timing from degradation despite the PMOS threshold voltage changes.
3Reliability
If reset signal function is incorporated into RC delay circuit, then NBTI stress degradation is reduced, but device complexity increases
Solution Approach 1:
The patent applies universality by designing the precharge transistor to serve multiple functions: it acts as a reset mechanism to clear the delay circuit state, functions as a precharge element to prepare the output node, and provides a pathway to mitigate NBTI stress degradation. This multi-functionality reduces the need for separate dedicated components.
Solution Approach 2:
The patent merges the reset function with the precharge function by using the same precharge transistor and control signal for both purposes. Instead of having separate reset circuitry and precharge circuitry, the invention combines these functions into a single integrated mechanism, thereby reducing overall device complexity while achieving the desired reliability improvement.
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 mitigates NBTI stress degradation, ensuring reliable operation by maintaining high voltage levels during stand-by modes and reducing timing instability in RC delay circuits, thereby enhancing the stability and reliability of semiconductor devices.
Implementation Method 1
the RC delay circuit 100 includes a first RC load inverter 106 and a second RC load inverter 120 having RC time constants
Implementation Method 2
Semiconductors often include resistive-capacitive (RC) delay circuits to introduce delay into control signals
Implementation Method 3
Negative bias temperature instability (NBTI) stress degradation, which affects the PMOS threshold voltage and drain current
Data Source
AI summary
Devices for generating a delay output signal are disclosed. A device may include a first delay circuit and a second delay circuit coupled in series between a first node and a second node in a delay path for the device, and having a third node therebetween. The device may also include a third circuit coupled to the third node and configured to charge the third node responsive to detecting a signal has passed through the first node and the third node. Associated semiconductor devices and methods are also disclosed.