Under Voltage Tolerant Clamp for IC Substrate Protection
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Solution Overview
Problem
Integrated circuits (ICs) are vulnerable to degradation due to excessive voltage exposure from electrostatic discharge (ESD) and inadvertent exposure to high or low supply voltages, which can lead to structural degradation and current surges through parasitic diodes.
Innovation Solution
An apparatus comprising an IC with a voltage clamp circuit and an under voltage circuit that sets the IC substrate voltage to a first voltage within a normal operating range when the external connection voltage is within that range, and to a second voltage when it exceeds or drops below zero volts, using high voltage transistors and diodes to limit current through parasitic diodes and maintain reverse bias.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a voltage clamp circuit is used to protect ICs from excessive voltage, then reliability is improved, but the circuit becomes vulnerable to under voltage conditions where parasitic diodes conduct current
Solution Approach 1:
The substrate connection acts as an intermediary element that is selectively coupled to the negative voltage supply rail through the under voltage detection circuit. This intermediary connection allows the substrate to be isolated from harmful negative voltage conditions while maintaining its normal function, preventing current surge through parasitic diodes without affecting the overall voltage clamping protection
Solution Approach 2:
The harmful effect of negative voltage on the substrate is extracted and isolated by selectively coupling the substrate connection to the negative voltage supply rail only when under voltage conditions are detected. This separates the substrate protection function from the general voltage clamping function, allowing independent optimization of each protection mechanism
2Ease of operation
If the substrate is connected to ground to maintain normal operation, then ease of operation is improved, but current flows through parasitic diodes during negative voltage events causing degradation
Solution Approach 1:
The substrate connection dynamically switches between ground connection and negative voltage supply rail connection based on voltage detection. The under voltage detection circuit controls this dynamic reconfiguration, allowing the substrate to adapt its connection state to prevailing voltage conditions, thereby maintaining ease of operation during normal conditions while preventing degradation during negative voltage events
Solution Approach 2:
The voltage parameter of the substrate connection is changed from ground potential to negative supply rail potential when under voltage conditions are detected. This parameter change is controlled by the under voltage detection circuit and prevents harmful current flow through parasitic diodes while maintaining proper substrate biasing for device operation
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
Effectively protects ICs from over and under voltage events by limiting current through parasitic diodes, reducing leakage current, and sustaining device junctions without significant degradation, as demonstrated by simulations showing reduced current draw during negative voltage conditions.
Implementation Method 1
The voltage clamp circuit is configured to clamp the voltage supply of one or more circuits internal to the IC to within a normal operating voltage range when the voltage of the external IC connection exceeds the normal operating voltage range
Implementation Method 2
limit current through parasitic diodes and maintain reverse bias
Implementation Method 3
limit current through parasitic diodes
Data Source
AI summary
An apparatus comprises an integrated circuit (IC) comprising an external IC connection, an IC substrate connection, a voltage clamp circuit and an under voltage circuit. The voltage of the IC substrate connection is set to a first voltage when a voltage of the external connection of the IC is within a normal operating voltage range. The voltage clamp circuit is configured to clamp the voltage supply of one or more circuits internal to the IC to within a normal operating voltage range when the voltage of the external IC connection exceeds the normal operating voltage range. The under voltage circuit is communicatively coupled to the clamp circuit and configured to set the voltage of the substrate to a second voltage when the voltage at the external IC connection of the IC is less than zero volts.