ESD Protection SCR with Dynamic Impedance Control
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Solution Overview
Problem
Current electrostatic discharge (ESD) protection circuits for integrated circuits are inadequate in effectively diverting large ESD currents and maintaining a low-impedance state without introducing leakage or requiring multiple diodes, limiting their applicability to low-voltage applications.
Innovation Solution
A protection circuit utilizing a silicon-controlled rectifier with a control circuit that places the device in a high-impedance state during power-on and a low-impedance state during power-off, utilizing a diode as a low-resistance ballast to manage current surges and divert ESD currents efficiently, with a turn-on voltage of less than 0.6 volts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a silicon-controlled rectifier is used to divert ESD currents, then the ESD protection capability is improved, but the device introduces leakage current and requires multiple diodes
Solution Approach 1:
The control circuit pre-biases the n-well to a first voltage level during powered operation to maintain the silicon-controlled rectifier in a high-impedance blocking state, preventing premature conduction and reducing leakage current before ESD events occur
Solution Approach 2:
The silicon-controlled rectifier dynamically transitions between high-impedance blocking state during powered operation and low-impedance conductive state during unpowered operation, adapting its electrical characteristics based on power supply conditions to optimize both leakage reduction and ESD protection
2Reliability
If the silicon-controlled rectifier is kept in low-impedance state to divert ESD currents, then ESD protection is improved, but leakage current increases during normal operation
Solution Approach 1:
The protection circuit dynamically adjusts the impedance state of the silicon-controlled rectifier based on power supply conditions: maintaining high-impedance blocking state during powered operation to minimize leakage, and transitioning to low-impedance conductive state during unpowered operation for optimal ESD protection
Solution Approach 2:
The control circuit monitors the power supply state and provides feedback control to the n-well bias voltage, automatically switching between blocking and conductive states to optimize the balance between leakage current reduction and ESD protection capability
3Reliability
If multiple diodes are used to maintain low-impedance state, then ESD protection is improved, but device complexity increases
Solution Approach 1:
The invention merges the ESD protection function with a single silicon-controlled rectifier device controlled by a compact control circuit, replacing the need for multiple discrete diodes and simplifying the overall circuit structure while maintaining effective ESD protection capability
Solution Approach 2:
The silicon-controlled rectifier serves multiple functions: it acts as a protective element during ESD events, a controlled switch for impedance management, and integrates with the control circuit to provide adaptive protection, reducing the need for separate dedicated components
4Adaptability or versatility
If the turn-on voltage is reduced to less than 0.6 volts, then the applicability to low-voltage applications is improved, but the ability to block normal signals may be compromised
Solution Approach 1:
The control circuit pre-biases the n-well to a first voltage level during powered operation that maintains the silicon-controlled rectifier in a high-impedance blocking state, preventing premature conduction at low voltages and ensuring normal signal blocking capability
Solution Approach 2:
The protection circuit dynamically adjusts the turn-on characteristics of the silicon-controlled rectifier based on power supply conditions, maintaining high blocking capability during powered operation with low turn-on voltage during unpowered operation to enable low-voltage application compatibility
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 solution provides effective ESD protection with reduced leakage and lower trigger voltage, enabling reliable operation across a wider voltage range and improving the safety window for ESD protection in integrated circuits.
Implementation Method 1
Electrostatic discharge (ESD) events can direct potentially large and damaging ESD currents to the sensitive integrated circuits of a chip
Implementation Method 2
The silicon-controlled rectifier triggers a shunting device to enter a low-impedance, conductive state. The ESD current is directed through the shunting device to ground
Implementation Method 3
supplying a first control logic to a well that includes an anode of a silicon-controlled rectifier such that the silicon-controlled rectifier is placed in a blocking state
Implementation Method 4
supplying a second control logic to the well that places the silicon-controlled rectifier in a low impedance state
Implementation Method 5
utilizing a diode as a low-resistance ballast to manage current surges and divert ESD currents efficiently, with a turn-on voltage of less than 0.6 volts
Data Source
AI summary
Circuits and methods of fabricating circuits that provide electrostatic discharge protection, as well as methods of protecting an integrated circuit from an electrostatic discharge event at an input/output pin. The protection circuit includes a silicon-controlled rectifier having a well and an anode in the well. The anode is coupled with the input/output pin. The protection circuit further includes a control circuit coupled with the well. The control circuit is configured to supply a first control logic voltage to the well that places the silicon-controlled rectifier in a blocking state, and a second control logic voltage to the well that places the silicon-controlled rectifier in a low impedance state. When placed in its low impedance state, the silicon-controlled rectifier is configured to divert current from the electrostatic discharge event at the input/output pin away from the integrated circuit.