Power-On Reset Circuit Using Quadratic and Logarithmic Currents
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Solution Overview
Problem
Typical power on reset (POR) circuits are prone to inaccuracy due to component variations and are susceptible to noise, with existing methods relying on voltage-centric comparisons that are not reliable or cost-effective for generating precise POR signals.
Innovation Solution
A method and apparatus using a current architecture that compares a first quadratic current with a second logarithmic current in relation to the power supply voltage to generate a reliable POR signal, allowing for voltage threshold monitoring and improving the accuracy of POR signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If voltage-centric comparison methods are used in POR circuits, then the circuit structure is simple, but the measurement precision and reliability of POR signals deteriorate due to component variations and noise susceptibility
Solution Approach 1:
The patent changes the comparison parameter from voltage to current, specifically comparing a quadratic current (proportional to the square of supply voltage) with a logarithmic current. This parameter transformation fundamentally improves measurement precision by creating current ratios that are inherently more stable and less sensitive to component variations and noise, while maintaining reasonable circuit complexity through standard current mirror and comparator implementations
Solution Approach 2:
The patent substitutes the traditional voltage-based detection mechanism with a current-based detection mechanism. By using current mirrors to generate proportional currents and comparing them through a current comparator, the system achieves superior noise immunity and precision. The current-based approach replaces the vulnerable voltage comparison with a more robust electrical quantity comparison that is less affected by parasitic elements and noise
2Ease of manufacture
If traditional voltage comparison methods are used, then the implementation is cost-effective, but the reliability of POR signals deteriorates due to susceptibility to noise and component variations
Solution Approach 1:
The patent transforms the detection parameter from voltage to current, using quadratic and logarithmic current relationships. This change maintains cost-effectiveness by utilizing standard semiconductor components and current mirror circuits, while dramatically improving reliability through current ratios that are inherently immune to supply voltage variations and noise, and less sensitive to component tolerance variations
3Device complexity
If voltage-centric POR circuits are used, then the device complexity is low, but the measurement precision deteriorates due to component variations
Solution Approach 1:
The patent changes from voltage comparison to current ratio comparison, where the quadratic current is proportional to the square of the supply voltage and the logarithmic current provides a reference. This parameter transformation achieves high manufacturing precision because the POR threshold is determined by the ratio of currents rather than absolute voltage levels, making it insensitive to component variations and process tolerances
Solution Approach 2:
The patent employs feedback mechanisms through current mirrors that automatically adjust the quadratic and logarithmic currents based on the supply voltage. This feedback ensures that the current ratios remain stable and accurate across varying operating conditions, improving manufacturing precision without requiring complex external calibration circuits
Data Source
AI summary
Aspects of the present invention include a method, apparatus and device for generating a power on reset (POR) signal in relation to the crossing point of two currents wherein at least one current is a quadratic function and the other is a logarithmic function, where each has a mathematical correlation to a function of the power supply voltage.