Stacked ESD Protection Circuit with Auxiliary Shunting Diodes
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Solution Overview
Problem
Existing electrostatic discharge (ESD) protection circuitry in electronic devices is susceptible to latchup and voltage overshoot due to parasitic capacitances, leading to potential damage from ESD events, and increasing the number of protection circuitry instances to mitigate this issue increases die area and introduces propagation delays.
Innovation Solution
A stacked configuration of ESD protection circuitry with auxiliary shunting diodes is used, where the diodes conduct a portion of the ESD current during the delay period before the stacked protection circuitry is fully activated, ensuring negligible current flow through the diodes once the circuitry is fully on, thus reducing voltage overshoot without increasing die area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple instances of protection circuitry are stacked to increase triggering voltage and holding voltage, then ESD protection capability is improved, but propagation delay increases due to parasitic capacitances
Solution Approach 1:
A coupling capacitor is introduced as an intermediary element between stacked protection circuitry instances. This capacitor enables voltage propagation through the stack during ESD events by temporarily storing and transferring charge, thereby reducing the propagation delay caused by parasitic capacitances while maintaining the elevated triggering and holding voltages provided by the stacked configuration.
2Loss of time
If a single protection circuitry instance is designed for higher triggering voltage and holding voltage, then propagation delay is reduced, but die area increases
Solution Approach 1:
The protection circuitry is segmented into multiple smaller instances connected in series (stacked configuration). Each instance operates at a lower voltage level, reducing the die area required for each individual component. The segmentation allows the system to achieve the desired high triggering and holding voltages through cumulative effect while keeping individual component sizes and total die area manageable.
3Reliability
If multiple instances of protection circuitry are stacked, then triggering voltage and holding voltage are increased, but voltage overshoot likelihood increases due to propagation delay
Solution Approach 1:
The coupling capacitor is pre-charged during normal operation to the appropriate voltage level. During an ESD event, this pre-charged capacitor immediately begins discharging to propagate the voltage change through the stacked protection circuitry instances, reducing the response time and preventing voltage overshoot before it can occur. The preliminary charging of the capacitor ensures rapid voltage propagation when needed.
Solution Approach 2:
The coupling capacitor acts as a mediator that smooths the voltage transition through the stacked protection circuitry. By temporarily storing and controlledly releasing charge, the capacitor prevents abrupt voltage changes that would cause overshoot, while still enabling the stacked instances to achieve their elevated triggering and holding voltage levels.
4Reliability
If discharge protection circuitry is designed to turn on at operating voltage, then protection is provided, but latchup susceptibility increases when holding voltage is less than design voltage
Solution Approach 1:
The protection circuitry is divided into multiple stacked instances, each contributing to the overall holding voltage. The cumulative holding voltage of the stacked instances exceeds the design voltage of the protected circuitry, ensuring that the protection circuitry turns off reliably after an ESD event and preventing latchup conditions where the protection would remain permanently activated.
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 reduces the likelihood of voltage overshoot and protects electronic devices from ESD events by ensuring that the stacked protection circuitry conducts all discharge current once fully activated, maintaining the desired level of protection without increasing die area or introducing significant delays.
Implementation Method 1
a first diode coupled between the third node and the fourth node
Data Source
AI summary
Protection circuits, device structures and related fabrication methods are provided. An exemplary protection circuit includes a first protection arrangement and a second protection arrangement. The first protection arrangement includes a first transistor having a first collector, a first emitter, and a first base coupled to the first emitter at a first node, and a second transistor having a second collector, a second emitter, and a second base coupled to the second emitter at a second node, the second collector being coupled to the first collector at a third node. The second protection arrangement is coupled electrically in series between the second node and a fourth node. The protection circuit further includes a first diode coupled between the third node and the fourth node.