Voltage Regulator Protection Circuit for Thin Oxide CMOS
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Solution Overview
Problem
Integrated circuits (ICs) with thin oxide devices are vulnerable to damage from voltage overshoots during battery insertion, as existing protection circuits fail to address voltage transients immediately after battery connection, and ICs lacking significant internal capacitance are particularly susceptible to excessive voltage overshoots.
Innovation Solution
A protection circuit comprising a capacitor, resistor, and transistor is coupled to the output of the voltage regulator, sensing the supply voltage to limit the output voltage to a regulated level during battery insertion, preventing damage to thin oxide devices by charging the capacitor quickly to prevent voltage overshoots.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the analog drive device is activated during battery insertion, then the regulator can quickly respond to power supply, but the output voltage overshoots the regulated level and damages thin oxide devices
Solution Approach 1:
The protection circuit applies preliminary anti-action by detecting battery insertion before the regulator fully activates and preemptively limiting the output voltage. The protection circuit monitors the power supply voltage and activates a clamping mechanism that prevents voltage overshoot before it can damage thin oxide devices, countering the harmful effect in advance.
Solution Approach 2:
The protection circuit acts as an intermediary between the regulator output and the thin oxide devices. It includes a detection circuit that monitors voltage conditions and a clamping circuit with a transistor that mediates the voltage level, allowing the regulator to operate at full speed while the intermediary protection circuit ensures the voltage never exceeds safe levels for thin oxide devices.
2Object-affected harmful factors
If significant internal capacitance is added to the regulator output, then voltage overshoots are reduced, but die area and current drain increase
Solution Approach 1:
Instead of changing the capacitance parameter of the regulator output, the invention changes the operational parameters of a protection circuit. It uses a transistor with controlled gate voltage and a resistor-capacitor time constant that is much smaller than traditional bulk capacitance would require. This achieves voltage overshoot protection through dynamic parameter control rather than static capacitance increase.
Solution Approach 2:
The invention extracts the voltage regulation function from the main regulator and places it in a separate protection circuit. This allows the regulator to maintain its original design without large output capacitance, while the extracted protection function handles voltage overshoot prevention independently, avoiding the die area penalty of adding bulk capacitance to the regulator.
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
The protection circuit effectively limits voltage overshoots during battery insertion, protecting thin oxide devices and allowing ICs without significant internal capacitance to operate safely, while having no impact on current drain or die area, and enabling the elimination of the power-out pin.
Implementation Method 1
A protection circuit (260) coupled to an output (230) of the voltage regulator (208). The protection circuit (260) comprises a capacitor (312), a resistor (324), and a transistor (316).
Data Source
AI summary
A circuit includes a voltage regulator (208) for outputting a voltage at a regulated level, a protection circuit (260), and a load circuit (210) coupled to the voltage regulator. The protection circuit includes means for preventing the voltage regulator from outputting a voltage at a level higher than the regulated level during a start-up period of the voltage regulator.