ESD Protection Circuit High Voltage Tolerance
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Solution Overview
Problem
Existing high voltage tolerant electrostatic discharge (ESD) protection circuits are limited by the voltage rating of their components, restricting the maximum operational voltage and thus failing to effectively protect integrated circuits from high voltage electrostatic discharges.
Innovation Solution
An ESD protection circuit incorporating an NPN transistor with a diode connection to ground, a PMOS transistor, and an R-C network with a voltage divider circuit, allowing the circuit to operate beyond its component voltage ratings by regulating gate voltages and providing a path for electrostatic discharges through the NPN transistor to ground.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the ESD protection circuit uses standard components (buffer, PFET, capacitor), then the circuit structure is simple and easy to manufacture, but the maximum operational voltage is limited to the voltage rating of the components
Solution Approach 1:
The ESD protection circuit is divided into multiple functional segments: a voltage detection circuit that monitors voltage levels, a control circuit that manages transistor switching, and a discharge path circuit that provides ESD protection. This segmentation allows each segment to be optimized for its specific function, enabling the overall circuit to operate at voltages higher than individual component ratings by distributing voltage stress across multiple components.
Solution Approach 2:
A control circuit acts as an intermediary between the voltage source and the discharge path transistor. This intermediary monitors voltage levels and selectively activates the discharge path only when needed, allowing the circuit to operate at high voltages during normal conditions while providing protection when voltage exceeds safe levels, without requiring all components to be rated for the maximum voltage.
2Reliability
If the circuit components are rated for high voltage to increase maximum operational voltage, then the reliability improves, but the device complexity and manufacturing difficulty increase
Solution Approach 1:
The circuit employs dynamic switching of the discharge path transistor based on real-time voltage detection. The transistor remains in a high-impedance state during normal operation to minimize circuit interference and power consumption, then switches to a low-impedance state when ESD conditions are detected. This dynamic behavior allows standard-voltage-rated components to be used while achieving high-voltage protection capability.
Solution Approach 2:
The circuit changes the operational parameters of the discharge path transistor based on detected voltage conditions. During normal operation, the transistor is biased to have high output impedance, effectively disconnecting it from the circuit. When voltage exceeds the threshold, the transistor parameter changes to low impedance, enabling ESD current to flow through the discharge path. This parameter switching allows components to operate within their voltage ratings while protecting against higher voltage transients.
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 enables protection of integrated circuits from electrostatic discharges beyond the voltage ratings of individual components, effectively safeguarding against high voltage pulses by utilizing a voltage divider circuit to regulate voltages and ensure proper transistor operation.
Implementation Method 1
allow an electrostatic discharge at the voltage source to flow through the NPN transistor to the ground
Implementation Method 2
The R-C circuit supplies the first gate voltage to the PMOS transistor when there is no electrostatic discharge to turn off the PMOS transistor and supplies the second gate voltage to the PMOS transistor responsive to the electrostatic discharge
Data Source
AI summary
An electrostatic discharge (ESD) protection circuit includes an NPN transistor having a collector terminal connected to a voltage source and an emitter terminal connected to the ground via a diode. The NPN transistor includes a base terminal for receiving a base current to turn on the NPN transistor to allow an electrostatic discharge at the voltage source to flow through the NPN transistor to the ground. The ESD protection circuit further includes a PMOS transistor having a source terminal coupled to the voltage source and a drain terminal coupled to the base terminal of the NPN transistor. The PMOS transistor includes a gate terminal for receiving a first and a second gate voltage. The ESD protection circuit further includes an R-C circuit coupled between the source voltage and the ground. The R-C circuit is configured to supply the first gate voltage to the PMOS transistor when there is no electrostatic discharge to turn off the PMOS transistor and the second gate voltage responsive to the electrostatic discharge to turn on the PMOS transistor for a predetermined time period. The ESD protection circuit further includes a voltage divider circuit coupled between the voltage source and the ground and coupled to the R-C circuit.