ESD Protection Circuit With Adjustable RC Time Constant
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Solution Overview
Problem
Existing ESD protection circuits face challenges in effectively draining ESD current during different tests and for various products, as the ESD stress duration varies across component-level and system-level tests, requiring an adjustable time constant to ensure effective protection.
Innovation Solution
An ESD protection circuit comprising resistors, capacitors, a driving circuit, and an ESD clamping device, with programmable switches that adjust the RC time constant based on the specific test or product requirements, allowing the ESD clamping device to selectively bypass ESD current according to a driving signal generated by the circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fixed RC time constant is used in the ESD protection circuit, then the circuit structure is simple, but the circuit cannot effectively drain ESD current for different test types and products with varying ESD stress durations
Solution Approach 1:
The patent applies the dynamics principle by making the RC time constant adjustable rather than fixed. Multiple resistors and capacitors are connected via switches that can be controlled to change the time constant value dynamically. This allows the ESD protection circuit to adapt its response characteristics to match different ESD stress durations for various test types (HBM, ESD gun, EFT, surge) and products, thereby improving protection effectiveness without requiring a completely different circuit design for each scenario.
Solution Approach 2:
The patent implements parameter changes by providing multiple discrete values for the RC time constant through different combinations of resistors and capacitors. The control circuit selectively connects specific resistor-capacitor pairs based on the required protection scenario, changing the electrical parameters of the circuit to optimize ESD current drainage for different stress durations and test conditions.
2Productivity
If the RC time constant is adjusted to match different ESD stress durations, then ESD current drainage effectiveness is improved, but the circuit complexity increases due to multiple resistors, capacitors, and switches
Solution Approach 1:
The patent applies segmentation by dividing the ESD protection circuit into multiple modular resistor-capacitor units, each contributing to the overall time constant. Instead of using one large complex RC network, the circuit is segmented into smaller discrete components that can be independently selected and combined. This modular approach allows flexible configuration to achieve different time constants while maintaining manageable circuit complexity through systematic component arrangement.
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 adjustable RC time constant enables effective ESD current drainage across different tests and products, ensuring robust protection for internal circuits by optimizing the response to varying ESD stress durations.
Implementation Method 1
a first node of each of a plurality of capacitors is connected a second supply voltage VSS, and a second node of each of at least a portion of capacitors C1 to CM is selectively connected to the input node Nin via a corresponding switch SWC2 to SWCM, respectively
Implementation Method 2
a first node of each of a plurality of resistors is connected to a first supply voltage VDD, and second nodes of the resistors R1 to RN are selectively connected to the input node Nin via corresponding switches SWR2 to SWRN, respectively
Implementation Method 3
the ESD clamping device 120 is arranged to selectively bypass an ESD current according to the driving signal VD
Data Source
AI summary
An ESD protection circuit includes a plurality of resistors, at least a capacitor, a driving circuit and an ESD clamping device, wherein a first node of each resistor is connected to a first supply voltage, and a second node of each of at least a portion of the resistors is selectively connected to an input node via a corresponding switch respectively, and a first node of the capacitor is connected to a second supply voltage, and a second node of the capacitor is connected to the input node; the driving circuit is arranged to generate a driving signal according to a voltage on the input node; and the ESD clamping device is coupled to the driving circuit, and connected between the first supply voltage and the second supple voltage, and the ESD clamping device is arranged to selectively bypass an ESD current according to the driving signal.