Bidirectional ESD Clamp Circuit for LIN Signal Passage
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Solution Overview
Problem
Conventional ESD protection circuits are inadequate for protecting against both positive and negative electrostatic discharge (ESD) events over a broad range of voltages, particularly in automotive electronics interfaced through a Local Interconnect Network (LIN) bus, where they must maintain high impedance during normal operation and switch to low impedance quickly during ESD events without external control.
Innovation Solution
An ESD protection circuit incorporating a p-channel field-effect transistor (PFET) clamp and an n-channel field-effect transistor (NFET) clamp, with a bias network that includes a Voltage Higher-Driver node to bias the DN-well, allowing the circuit to clamp both positive and negative ESD events by switching between high and low impedance modes as needed, while passing signal voltages without interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional ESD protection circuits are used, then protection against ESD events is provided, but they cannot protect against both positive and negative ESD events over a broad voltage range while maintaining signal passage capability
Solution Approach 1:
The ESD protection circuit is segmented into multiple specialized clamp circuits: a positive voltage clamp (PFET-based) for clamping positive ESD events, a negative voltage clamp (NFET-based) for clamping negative ESD events, and a bidirectional clamp for handling both polarities. Each clamp is optimized for specific voltage ranges and ESD scenarios, allowing the system to effectively protect against both positive and negative ESD events across a broad voltage range while maintaining signal passage capability during normal operation
Solution Approach 2:
The protection circuit employs universal clamp structures that can handle multiple functions: the PFET clamp serves both as a positive ESD protector and a signal passage path, the NFET clamp provides negative ESD protection while allowing negative signal passage, and the bidirectional clamp offers comprehensive protection for both polarities. This multi-functionality enables a single integrated circuit to protect against both positive and negative ESD events over a broad voltage range (−28V to +42V) while maintaining full signal passage capability during normal LIN bus operation
2Speed
If the protection circuit stays open circuit during normal operation, then signal passage is enabled, but the circuit must switch to low impedance mode quickly during ESD events without external control
Solution Approach 1:
The clamp circuits are pre-configured with biasing networks that maintain them in a high-impedance standby state during normal operation, ready to activate immediately upon ESD detection. The PFET clamp is pre-biased to activate at positive ESD voltages, the NFET clamp is pre-biased for negative ESD detection, and the bidirectional clamp is pre-positioned to respond to either polarity. This preliminary preparation enables nanosecond-level response times without requiring external control signals
Solution Approach 2:
The ESD protection circuit is self-regulating through automatic voltage-level detection and self-activation mechanisms. The biasing networks continuously monitor the voltage at the protected pin and automatically activate the appropriate clamp (positive, negative, or bidirectional) when ESD conditions are detected, without requiring external control inputs. The circuit self-manages the transition from high-impedance signal passage mode to low-impedance ESD clamping mode based solely on the voltage conditions at the protected pin
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 effectively protects against both positive and negative ESD events across a wide voltage range, ensuring safe signal passage and rapid response during ESD events without external control, making it suitable for automotive electronics interfaced with LIN buses.
Implementation Method 1
electrostatic discharge (ESD) events
Implementation Method 2
p-channel field-effect transistor (PFET) clamp coupled to a pin to be protected, the PFET clamp including a number of PFETs in a DN-well, an n-channel field-effect transistors (NFET) clamp coupled between ground and the pin through the PFET clamp
Data Source
AI summary
An electrostatic discharge protection circuit capable of clamping both positive and negative ESD events and passing signals is provided. Generally, the circuit includes a p-channel field-effect transistor (PFET) clamp coupled to a pin to be protected, the PFET clamp including a plurality of PFETs in a DN-well, an n-channel field-effect transistors (NFET) clamp coupled between ground and the pin through the PFET clamp, the NFET clamp including a plurality of NFETs coupled in series, and a bias network for biasing a voltage of the DN well to substantially equal a voltage on the pin when the voltage on the pin is greater than ground potential, and to ground potential when the pin voltage is less than ground potential. The plurality of are PFETs coupled in parallel between the pin and the NFET clamp, each of the PFETs is coupled to the pin though one of a plurality ballast resistors.