Capacitive Voltage Detection Circuit for Low-Current Power-On Reset
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Solution Overview
Problem
Conventional voltage detection circuits in semiconductor devices face challenges in reducing area and current consumption while preventing erroneous operation due to unstable reference voltages and ongoing current flow, which leads to inefficient power-on reset functions.
Innovation Solution
A voltage detection circuit incorporating a capacitive element coupled with a current mirror circuit and switching elements, where the capacitive element is charged only when the input voltage exceeds a threshold, delaying the enable signal activation and reducing current consumption after charging is complete.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional voltage detection circuits use resistive elements to maintain stable reference voltage detection, then detection reliability is improved, but semiconductor chip area is largely occupied
Solution Approach 1:
The patent changes the detection mechanism from resistive voltage division to capacitive charging time measurement. By measuring the time required for a capacitor to charge to a threshold voltage through a known current source, the circuit detects voltage stability without requiring large resistive elements. This parameter change from spatial (resistance value) to temporal (charging time) domain resolves the area-reliability contradiction.
Solution Approach 2:
The patent replaces the resistive voltage detection mechanism with a capacitive timing mechanism controlled by switching elements. Instead of using resistors to establish voltage levels, the circuit uses a capacitor charging process controlled by switches to detect when the reference voltage becomes stable. This substitution eliminates the need for large resistive elements while maintaining detection reliability.
2Reliability
If conventional voltage detection circuits use series circuits with resistive elements and diodes to detect voltage rising, then voltage detection function is achieved, but current consumption continues to flow
Solution Approach 1:
The patent implements periodic action through switching elements that periodically charge and discharge the capacitive element based on voltage threshold detection. The switching elements activate only when the reference voltage exceeds predetermined thresholds, creating periodic charging cycles instead of continuous current flow. This periodic operation maintains voltage detection functionality while eliminating continuous current consumption.
Solution Approach 2:
The patent extracts the continuous current path by introducing switching elements that isolate the capacitive charging circuit from the power supply when voltage thresholds are met. The switching elements effectively remove the charging current path from the active circuit, stopping current flow while preserving the voltage detection capability through the charged state of the capacitive element.
3Area of stationary object
If voltage detection circuit uses small electrostatic capacitance to reduce area, then area is reduced, but delay time for enable signal activation may be insufficient
Solution Approach 1:
The patent changes the controlling parameter from capacitive value to current magnitude. By using a larger current to charge a small capacitor, the circuit achieves the required delay time without increasing capacitance. The delay time is determined by the ratio of capacitance to current (t = C×V/I), so increasing the current allows the use of smaller capacitors while maintaining the same charging time. This parameter change resolves the area-time contradiction.
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
This configuration effectively reduces both area and current consumption, minimizing erroneous operations and ensuring accurate activation of the reference voltage and current supply, thereby enhancing the reliability of power-on reset functions in semiconductor devices.
Implementation Method 1
a capacitive element coupled in series to the current mirror circuit, and charged with the current flowing through the switching element
Data Source
AI summary
A voltage detection circuit includes a reference voltage and current supply configured to generate a reference voltage and a reference current; a switching element configured to shift from an off-state to an on-state when the reference voltage is higher than a predetermined threshold voltage; a current mirror circuit allowing a current corresponding to the reference current to flow through the switching element in the on-state; a capacitive element coupled in series to the current mirror circuit and charged with the current flowing through the switching element; and an inverter configured to output an enable signal activated based on a terminal voltage of the capacitive element.