MOS Power-On Reset Circuit With Zero-Temp-Coefficient Reference
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Solution Overview
Problem
Existing power-on reset (POR) circuits and reference signal generators using bandgap circuits composed of bipolar transistors are complex, consume high operating current, and are costly.
Innovation Solution
A POR circuit and reference signal circuit utilizing MOS transistors with specific threshold voltages and bias currents to generate signals with zero temperature coefficient, achieving low power consumption and simplified design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If bandgap circuits composed of bipolar transistors are used to generate POR threshold or reference voltage, then low temperature coefficient is achieved, but circuit complexity increases, operating current increases, and cost increases
Solution Approach 1:
The patent changes the operating parameters of MOS transistors by biasing them in the subthreshold region and carefully selecting aspect ratios and bias currents to achieve zero temperature coefficient. This replaces the need for complex bipolar bandgap circuits while maintaining temperature stability through parameter optimization of simpler MOS devices.
Solution Approach 2:
The patent substitutes bipolar transistor-based bandgap circuits with MOS transistor-based circuits. This replacement eliminates the need for bipolar device complexity while achieving the same temperature compensation function through MOS transistor characteristics and circuit topology design.
2Stability of the object's composition
If bandgap circuits composed of bipolar transistors are used to generate POR threshold or reference voltage, then low temperature coefficient is achieved, but operating current increases
Solution Approach 1:
The patent exploits the subthreshold region operation of MOS transistors, which inherently consumes much lower current than bipolar transistors. By operating in this specific parameter region and optimizing bias currents, the circuit achieves zero temperature coefficient with dramatically reduced operating current consumption.
3Stability of the object's composition
If bandgap circuits composed of bipolar transistors are used to generate POR threshold or reference voltage, then low temperature coefficient is achieved, but cost increases
Solution Approach 1:
The patent replaces expensive bipolar transistor fabrication processes with standard MOS transistor processes. This substitution leverages the simpler, more cost-effective MOS manufacturing technology while achieving the same temperature stability function through circuit design and parameter optimization.
Solution Approach 2:
The patent uses standard MOS transistors, which are cheaper and more readily available than bipolar transistors. By optimizing the circuit design to achieve zero temperature coefficient with these simpler, less expensive devices, the overall manufacturing cost is reduced while maintaining performance.
4Use of energy by moving object
If MOS transistors are biased in subthreshold region to reduce power consumption, then operating current decreases, but transistor threshold voltage variability increases
Solution Approach 1:
The patent employs feedback mechanisms through the circuit topology where the threshold voltage differences between matched MOS transistors are compensated. The circuit is designed to sense and compensate for threshold voltage variations, ensuring stable operation despite the inherent variability of subthreshold MOS transistors.
Solution Approach 2:
The patent carefully selects specific aspect ratios and bias currents for individual MOS transistors to optimize their characteristics. By tailoring the local parameters of each transistor (W/L ratios, bias currents) and operating them in the subthreshold region, the circuit achieves both low power consumption and stable threshold voltage behavior through localized parameter optimization.
Data Source
AI summary
A power-on reset (POR) circuit includes: a signal generator circuit for generating a first and a second signal according to an input voltage, and a comparator circuit. The comparator circuit, having a non-zero input offset, includes a first MOS transistor with a first conductive type and having a first conductive type gate and a first threshold voltage, and a second MOS transistor with a first conductive type and having a second conductive type gate and a second threshold voltage. The input offset relates to a difference between the first and the second threshold voltage. The first and the second signal control the first and the second MOS transistors respectively to generate a POR signal. When the input voltage exceeds a POR threshold which relates to a predetermined multiple or ratio of the input offset, the POR signal transits its state.