Current-Comparison Voltage Supervisor With Low Off-State Current
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Solution Overview
Problem
Conventional voltage supervisors face issues with high off-state currents, slow response times, difficulty in realizing small threshold voltages, and large silicon area usage, making them inefficient for monitoring power supply voltages effectively.
Innovation Solution
A voltage supervisor circuit topology with four branches, utilizing two currents proportional to gate-to-source voltage differences and supply voltage differences, allowing for quick response, low off-state currents, and programmable threshold voltages, while maintaining a compact silicon area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional voltage supervisor circuits are used, then voltage monitoring function is provided, but off-state current is high
Solution Approach 1:
The patent changes the operating parameters of the transistors by utilizing the threshold voltage difference between enhancement mode and depletion mode MOSFETs. This parameter change enables the circuit to achieve low off-state current while maintaining reliable voltage monitoring through the unique electrical characteristics of the mixed-mode transistor configuration.
Solution Approach 2:
The patent employs a composite structure combining enhancement mode and depletion mode MOSFETs in a single circuit topology. This composite approach leverages the complementary characteristics of both transistor types to achieve low quiescent current operation while preserving the voltage supervision function.
2Speed
If conventional voltage supervisor circuits are used, then voltage threshold detection is provided, but response time is slow
Solution Approach 1:
The patent replaces conventional voltage comparison mechanisms with a current-based detection system. By converting voltage differences into current signals through the transistor network, the circuit achieves faster response times while maintaining detection accuracy through the direct relationship between current and voltage in the transistor operating region.
Solution Approach 2:
The patent changes the detection parameter from direct voltage comparison to current measurement. This parameter transformation enables faster response by utilizing the rapid current response characteristics of MOSFETs while maintaining accurate threshold detection through the consistent current-voltage relationship in the transistor operation.
3Adaptability or versatility
If conventional voltage supervisor circuits are used, then fixed threshold voltage is provided, but adaptability to different thresholds is poor
Solution Approach 1:
The patent creates a universal voltage supervisor circuit that can monitor multiple different voltage thresholds using the same basic topology. The circuit achieves this universality by utilizing the controllable threshold voltage characteristics of the depletion mode transistor, which can be adjusted to detect different voltage levels without requiring circuit redesign.
Solution Approach 2:
The patent introduces dynamic adjustability to the voltage threshold detection by leveraging the controllable properties of the depletion mode MOSFET. This dynamic characteristic allows the circuit to adapt to different voltage thresholds by changing the operating point or configuration of the depletion mode transistor, providing versatility without increasing fundamental circuit complexity.
4Area of stationary object
If conventional voltage supervisor circuits are used, then voltage monitoring is provided, but silicon area is large
Solution Approach 1:
The patent merges multiple functions into a single integrated transistor network. By combining the reference voltage generation, current comparison, and threshold detection functions within a compact transistor-resistor network, the circuit achieves accurate voltage monitoring with minimal silicon area utilization.
Solution Approach 2:
The patent employs a nested configuration where the depletion mode transistor is effectively nested within the enhancement mode transistor circuitry. This nested structure allows the circuit to achieve complex voltage supervision functionality in a compact form factor by sharing common circuit elements and transistor regions.
Data Source
AI summary
A voltage supervisor includes a first transistor coupled between a first supply voltage and a second supply voltage. The voltage supervisor includes a second transistor coupled between the first supply voltage and the second supply voltage. The voltage supervisor is configured to provide a first current proportional to a difference in gate-to-source voltages of the first transistor and the second transistor. The voltage supervisor is also configured to provide a second current proportional to a difference in the first supply voltage and the difference in gate-to-source voltages of the first transistor and the second transistor. The voltage supervisor is configured to compare the first current to the second current to determine a voltage value that changes a state responsive to the first supply voltage crossing a threshold.