Bidirectional ESD Device With Parallel Switch Legs
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Solution Overview
Problem
Existing electrostatic discharge (ESD) devices in integrated circuits face challenges in shunting large currents during ESD events while maintaining a desired size, and preventing current crowding, which affects their performance in both positive and negative voltage events.
Innovation Solution
A bidirectional ESD device with multiple parallel switch legs, where each switch leg consists of a first current switch and a second current switch in a back-to-back configuration, providing ballast functions for each other during opposite polarity events, with independent current collection nodes to prevent voltage drops and promote uniform conduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the ESD device is designed to shunt large current, then the current capacity is improved, but the device size increases
Solution Approach 1:
The ESD device is divided into multiple parallel switch legs, with each leg containing series-connected current switches. This segmentation allows the total current capacity to be distributed across multiple smaller parallel paths, achieving high current handling capability while maintaining a compact overall device footprint.
2Power
If multiple current switches are connected in parallel to increase current capacity, then the current handling capability is improved, but current crowding occurs
Solution Approach 1:
The device uses multiple parallel switch legs with isolated current collection nodes, segmenting the current paths to prevent interaction between legs. This ensures uniform current distribution across all switches.
Solution Approach 2:
Each switch leg is designed with specific local characteristics including isolated current collection nodes and ballast resistors, creating locally optimized current distribution paths that prevent current crowding while maintaining overall high current capacity.
3Duration of action of stationary object
If the ESD device is designed for sustained ESD events, then the duration of protection is improved, but voltage drops increase
Solution Approach 1:
Multiple parallel switch legs with isolated current collection nodes segment the voltage drop across each leg, preventing cumulative voltage drops that would occur in series configurations. This allows sustained protection while maintaining acceptable voltage levels.
Solution Approach 2:
Each switch leg incorporates ballast resistors and isolated current collection nodes with specific local electrical characteristics, creating locally optimized voltage distribution that prevents excessive voltage drops during sustained ESD events.
Data Source
AI summary
An integrated circuit includes a bidirectional ESD device which has a plurality of parallel switch legs. Each switch leg includes a first current switch and a second current switch in a back-to-back configuration. A first current supply node of each first current switch is coupled to a first terminal of the ESD device. A second current supply node of each second current switch is coupled to a second terminal of the ESD device. A first current collection node of each first current switch is coupled to a second current collection node of the corresponding second current switch. The first current collection nodes in each first current switch is not coupled to any other first current collection node, and similarly, the second current collection node in each instance second current switch is not coupled to any other second current collection node.