Avalanche SCR ESD Circuit With Zener Trigger for Low-Capacitance HV ICs
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Solution Overview
Problem
Implementing integrated high voltage (HV) electrostatic discharge (ESD) protection for integrated circuit (IC) devices poses challenges in achieving low capacitance, high current/power capability, and high electromagnetic immunity while maintaining a compact design and robustness, especially for high-speed communication applications.
Innovation Solution
The proposed solution involves an ESD protection circuit using a two-terminal semiconductor controlled rectifier (SCR) device with an avalanche breakdown voltage for self-turn on, combined with a parallel connected static trigger control circuit (TCC) comprising a series chain of Zener diodes, which operates independently without gate triggering, ensuring robustness and reduced area occupancy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional ESD protection circuits are used, then high current capability is achieved, but area occupancy increases and capacitance increases
Solution Approach 1:
The ESD protection circuit is segmented into two parallel paths: a first circuit path with higher activation voltage for low-current scenarios and a second circuit path with lower activation voltage for high-current ESD events. This segmentation allows the circuit to handle different current levels efficiently, reducing overall area occupancy while maintaining high current capability when needed.
Solution Approach 2:
The circuit implements partial action by having the second circuit path activate only when ESD current exceeds a threshold level. The first circuit path handles normal operation and low-level events, while the second path provides excessive current handling capability only when necessary, thus reducing area occupancy compared to always having full current capability circuitry active.
2Reliability
If traditional ESD protection circuits are used, then high current capability is achieved, but capacitance increases
Solution Approach 1:
The protection circuit is divided into two paths with different capacitance characteristics. The first circuit path has lower capacitance for high-speed signals, while the second path provides high current capability with controlled capacitance. This segmentation allows the circuit to maintain low overall capacitance while preserving high current capability when ESD events occur.
Solution Approach 2:
The high current capability path is designed to activate only when excessive current is detected, rather than being continuously active. This partial action approach minimizes the impact of capacitance on high-speed signals during normal operation, while still providing robust ESD protection when needed.
3Reliability
If avalanche SCR device with self-turn on is used, then robustness is improved, but immunity to unwanted triggering must be maintained
Solution Approach 1:
The circuit assigns different activation voltage characteristics to different paths: the first circuit path has higher activation voltage providing immunity to unwanted triggering from inductive effects, while the second circuit path has lower activation voltage for robust ESD protection. This local quality differentiation allows the system to maintain robustness while resisting false triggering.
Solution Approach 2:
The circuit acts as an intermediary between the avalanche SCR device's self-turn on capability and the need for immunity to unwanted triggering. By implementing a two-path architecture with different activation thresholds, the circuit mediates between the robust but sensitive avalanche device and the requirement for immunity to electromagnetic interference and inductive effects.
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
This configuration effectively enhances the ESD protection by providing high immunity to electromagnetic events and reducing the occupied area by 15-25% compared to traditional designs, while maintaining high current carrying capacity and immunity to unwanted triggering.
Implementation Method 1
the circuit path comprises a series connected chain of M Zener diodes; wherein the SCR device has an avalanche breakdown voltage for turn on, said avalanche breakdown voltage set by a breakdown avalanche of a PN junction of the SCR device; wherein the circuit path has an activation voltage for turn on, said activation voltage being dependent on M times a Zener diode reverse breakdown voltage
Implementation Method 2
said first SCR device has an avalanche breakdown voltage for self-turn on
Data Source
AI summary
A two terminal semiconductor controlled rectifier (SCR) device has an anode terminal coupled to a first node and a cathode terminal coupled to a second node. Neither of the cathode gate or anode gate of the SCR device are connected to a triggering circuit for controlling turn on of the SCR device. The SCR device has an avalanche breakdown voltage for turn on, where that avalanche breakdown voltage is set by a breakdown avalanche of a PN junction of the SCR device. A circuit path includes a series connected chain of M Zener diodes with a blocking diode that are coupled between the first node and the second node. The circuit path has an activation voltage for turn on, where that activation voltage is dependent on N times a Zener diode reverse breakdown voltage. The activation voltage is less than the avalanche breakdown voltage.