Power-Up Signal Circuit Hysteresis for Stable Reset Thresholds
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Solution Overview
Problem
Conventional power up signal generation circuits in semiconductor devices experience significant variations in target voltage levels due to process, voltage, and temperature conditions, leading to unpredictable resets or failure to detect power off states, causing malfunctions.
Innovation Solution
A power up signal generation circuit with a first and second voltage detection unit to set predetermined target voltage levels, using a control signal to maintain or reset the power up signal, ensuring stable operations by fixing the second target voltage level through a control signal generated based on the external power supply voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single target voltage level is used for power up signal transition, then the circuit structure is simple, but the power up signal may be reset unexpectedly due to voltage drops or may not reset properly during power off
Solution Approach 1:
The single target voltage level is segmented into two distinct levels: a first target voltage level for power-on detection and a second target voltage level for power-off detection. This segmentation allows the circuit to differentiate between power-on and power-off states, preventing unexpected resets during voltage drops and ensuring proper reset during power-off, thereby resolving the reliability issue without significantly increasing circuit complexity.
Solution Approach 2:
The circuit dynamically adjusts the target voltage level based on the operational state. During power-on, the first target voltage level is used; during power-off, the second target voltage level is used. This dynamic adjustment enables the circuit to adapt to different operational conditions, improving the stability and reliability of the power up signal while maintaining a relatively simple circuit structure.
2Reliability
If the target voltage level is designed with hysteresis characteristic to prevent unexpected resets, then the power up signal stability is improved, but the circuit complexity increases due to additional detection units
Solution Approach 1:
The voltage detection function is segmented into two separate units: a first voltage detection unit for detecting the first target voltage level and a second voltage detection unit for detecting the second target voltage level. This segmentation enables the circuit to implement hysteresis characteristic by using different detection thresholds for power-on and power-off states, improving power up signal stability while keeping the circuit structure manageable through functional division.
Solution Approach 2:
The voltage detection units are designed to perform multiple functions: the first voltage detection unit detects the first target voltage level during power-on, and the second voltage detection unit detects the second target voltage level during power-off. This multi-functionality allows the circuit to achieve hysteresis characteristic and improve reliability without requiring entirely separate detection circuits, thereby controlling the increase in circuit complexity.
3Device complexity
If the second target voltage level is determined by NMOS transistor characteristics, then the circuit is simple, but the target voltage level varies with process, voltage, and temperature conditions
Solution Approach 1:
The circuit employs feedback mechanisms where the detected voltage levels are fed back to control the power up signal transitions. The first and second voltage detection units continuously monitor the power supply voltage and provide feedback signals to the control logic, ensuring that the target voltage levels remain consistent despite variations in process, voltage, and temperature conditions. This feedback approach maintains manufacturing precision without significantly increasing circuit complexity.
Solution Approach 2:
The circuit changes the detection parameter from relying solely on NMOS transistor characteristics to using explicitly defined first and second target voltage levels. By setting these voltage levels as fixed reference points rather than depending on transistor threshold variations, the circuit achieves consistent target voltage levels across different process, voltage, and temperature conditions, thereby improving manufacturing precision while maintaining circuit simplicity.
Data Source
AI summary
A power up signal generation circuit transits a power up signal at a predetermined target voltage level by providing a predetermined hysteresis characteristic to the target voltage level of a power supply voltage corresponding to the power up signal. The power up signal generation circuit includes a first voltage detection unit that detects a first target voltage level of a power supply voltage to output a detection signal. The circuit also includes a second voltage detection unit that detects a second target voltage level of the power supply voltage in response to a power up signal to output a control signal, wherein the second target voltage level is lower than the first target voltage level. A power up signal drive unit of the circuit activates the power up signal in response to the detection signal and drives the power up signal in response to the control signal.