IC Input Protection Circuit for Negative Voltage Interference
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Solution Overview
Problem
During negative current tests on integrated circuits (ICs), external negative voltage can disturb internal circuit signals and cause malfunctions by entering through the bonding pad.
Innovation Solution
A protection circuit comprising a transistor, voltage selector, inverter, resistor, and switch circuit is coupled to the input end, which outputs a lower voltage or boosts the output to a preset voltage when negative voltage is detected, preventing it from entering the internal circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If negative current test is performed on the bonding pad, then the bonding pad can be tested for current extraction, but negative voltage enters the internal circuit and causes malfunction
Solution Approach 1:
The patent introduces a protection circuit as an intermediary component between the bonding pad and the internal circuit. This protection circuit includes a transistor and associated circuitry that detects negative voltage at the bonding pad and activates to block or clamp the negative voltage before it can enter the internal circuit, thus mediating the interaction between the test equipment and the vulnerable internal circuitry
Solution Approach 2:
The protection circuit is designed to detect negative voltage conditions and activate preliminary protective actions before the negative voltage can cause damage to the internal circuit. The circuit monitors the bonding pad voltage and preemptively engages protection mechanisms such as transistor switching or voltage clamping to prevent the harmful negative voltage from propagating inward
2Reliability
If protection circuit is added to prevent negative voltage, then internal circuit is protected from malfunction, but device complexity increases
Solution Approach 1:
The protection circuit is designed to perform multiple functions within a single integrated structure. It not only protects against negative voltage but also maintains normal signal transmission during positive voltage operation, provides electrostatic discharge protection, and can be integrated with existing bonding pad structures, making it a multi-functional component that adds protection without proportionally increasing complexity
Solution Approach 2:
The protection circuit components are nested within the existing IC structure, with the protection circuitry integrated around the bonding pad input. The transistor, voltage selector, and associated components are arranged in a nested configuration where smaller components are embedded within larger structural elements, minimizing the overall footprint and reducing the apparent complexity increase
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 prevents negative voltage from entering the internal circuit, thereby avoiding malfunctions and ensuring normal operation without disturbing signal transmission or interfering with existing electrostatic discharge protection.
Implementation Method 1
The voltage selector is coupled to the transistor and the input end of the protection circuit, and outputs a lower one of a voltage at the input end of the protection circuit and a ground voltage to the transistor
Implementation Method 2
The inverter is coupled to the transistor... When the voltage at the input end is lower than 0, the second protection circuit boosts the output end to a preset voltage
Implementation Method 3
The switch circuit is coupled to the inverter, a preset voltage and an output end of the protection circuit and controlled by the inverter to connect the preset voltage to the output end of the protection circuit or to switch the output end of the protection circuit to a floating state
Implementation Method 4
The first protection circuit is coupled between the bonding pad and a ground end of the IC, so as to provide electrostatic discharge (ESD) protection
Data Source
AI summary
An input circuit suitable for an integrated circuit (IC) and a protection circuit in the input circuit are provided. The protection circuit includes a transistor, a voltage selector, an inverter, a resistor and a switch circuit. The transistor is coupled to an input end of the protection circuit. The voltage selector is coupled to the transistor and the input end of the protection circuit, and outputs a lower one of a voltage at the input end of the protection circuit and a ground voltage to the transistor. The inverter is coupled to the transistor. The resistor is coupled between a power supply voltage and the inverter. The switch circuit is coupled to the inverter, a preset voltage and an output end of the protection circuit and is controlled by the inverter to connect the preset voltage to the output end or to switch the output end to a floating state.