Negative Voltage Clamp for Single-Supply Over-Voltage Protection
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Solution Overview
Problem
Current over-voltage protection circuits for integrated chips rely on external supply voltages, which are costly and complex, and introduce inefficiencies and noise, while also requiring multiple independent voltage sources.
Innovation Solution
A single-supply system with a negative voltage clamp that generates a negative reference voltage from a positive supply, using a current limiting resistor and a voltage clamp circuit to prevent over-voltage by shunting current to the positive supply, eliminating the need for external negative supplies and reducing noise and inefficiencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If external supply voltages are used for over-voltage protection, then protection capability is improved, but system complexity and cost increase
Solution Approach 1:
The patent combines the over-voltage protection function with the existing single positive supply voltage, eliminating the need for separate external supply voltages. The clamp circuit uses the available positive supply to establish both the operating range and protection threshold, merging multiple functions into a unified approach that reduces component count and system complexity.
Solution Approach 2:
The positive supply voltage serves dual purposes: it provides the operating voltage for the circuit and simultaneously establishes the reference for over-voltage protection. This multi-functional use of a single supply eliminates the need for dedicated protection voltages, reducing the number of independent sources required while maintaining comprehensive protection capability.
2Reliability
If input attenuation resistors are used, then over-voltage protection is improved, but noise and linearity errors increase
Solution Approach 1:
The patent introduces a clamp circuit as an intermediary protective element that activates only when over-voltage conditions occur. This mediator provides protection without being continuously present in the signal path, thereby avoiding the continuous noise and linearity degradation caused by attenuation resistors while still preventing damage during voltage excursions.
Solution Approach 2:
The clamp circuit dynamically transitions between high-impedance (inactive) and low-impedance (active) states based on the input voltage level. During normal operation, the clamp remains high-impedance and does not affect signal integrity, but automatically activates when voltage exceeds the threshold, providing dynamic protection without the continuous signal degradation inherent in resistive attenuation approaches.
3Measurement precision
If multiple independent voltage sources are used, then protection accuracy is improved, but power consumption and cost increase
Solution Approach 1:
The system uses its own single positive supply voltage to establish the protection threshold, eliminating the need for external reference voltages. The clamp circuit derives its reference directly from the operating supply, making the system self-sufficient and reducing power consumption associated with multiple independent voltage sources while maintaining accurate protection relative to the actual operating conditions.
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
Provides accurate over-voltage protection in both positive and negative directions with a single positive supply, simplifying driver circuitry and reducing costs while maintaining reliability and power efficiency.
Implementation Method 1
A voltage clamp circuit, in shunt with the current limiting resistor, performs clamping on the input by transitioning from high impedance to low impedance when the input voltage to the integrated circuit exceeds a maximum voltage level threshold or reference either in the positive or negative direction
Implementation Method 2
A current limiting resistor, coupled to the external voltage input, is designed to protect the integrated circuit from voltages that exceed the maximum voltage level threshold of the integrated circuit by causing a voltage drop across the resistor
Implementation Method 3
A reference generator generates a reference voltage wherein a voltage inverting charge pump inverts the reference voltage around ground in the circuit
Implementation Method 4
A clamp detector detects a negative voltage that exceeds a corresponding threshold voltage and, in response thereto, shunts current from the voltage node to the positive supply such that the negative voltage is clamped
Data Source
AI summary
A system, apparatus and a method are described that provide a voltage clamp for a single-supply system. In particular, a negative voltage clamp prevents a negative over-voltage in a system having only a positive independent voltage source. For example, certain analog-to-digital converters and other circuits allow input signals below the negative supply, or ground in single-supply systems, either by direct sampling or using input attenuation resistors. The negative clamp allows the circuit to provide accurate negative over-voltage protection and the absence of this claim would result in over-voltage protection in positive voltage directions only.