Level Shifter ESD Protection via Power Network Extraction
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Solution Overview
Problem
Level shifters in high power supply voltage domains are vulnerable to damage during electrostatic discharge (ESD) events due to excessive voltage differentials across domain boundaries, and existing solutions like local ESD clamps can introduce delays and affect signal timing.
Innovation Solution
Incorporating devices responsive to ESD signals to manage voltage differentials during ESD events, eliminating the need for ESD clamps on signal paths by using a voltage detection circuit and ESD circuitry to activate clamps for discharge, thereby preventing damage and maintaining normal operating performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If local ESD clamps are implemented to protect level shifters during ESD events, then device protection is improved, but signal timing is worsened due to parasitic capacitances and resistances
Solution Approach 1:
The invention extracts the ESD protection function from the signal path by placing ESD clamps on power supply paths instead. This separates the protection function from the signal transmission path, eliminating the parasitic effects that would degrade signal timing while maintaining ESD protection capability.
Solution Approach 2:
The invention uses the power supply network as an intermediary to provide ESD protection. Instead of placing clamps directly on signal paths, the ESD clamps are placed on power supply paths, using the power network as a mediator to dissipate ESD energy away from sensitive signal paths.
2Reliability
If ESD clamps are placed on signal paths to limit voltage differentials, then device protection is improved, but device complexity is worsened
Solution Approach 1:
The invention makes the power supply network multi-functional by using it both for its primary purpose of powering the circuit and as a pathway for ESD protection. This eliminates the need for separate ESD protection circuits on signal paths, reducing overall device complexity.
Solution Approach 2:
The invention merges the ESD protection function with the existing power supply distribution network. By combining these functions, the design avoids adding separate protection circuits, thereby reducing device complexity while maintaining protection capability.
Data Source
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AI summary
As disclosed herein, a level shift circuit (205) includes devices that are responsive to an ESD signal (217out: Trigger) for placing those devices in a specific condition in response to the ESD signal indicating an ESD event (ESD on Pads 215, 229). In some embodiments, the devices are transistors in current paths that are placed in a condition such that during an ESD event, voltage differentials in the current paths across voltage domain boundaries do not damage the circuitry of the level shift circuit. In some embodiments, some of the same devices that are responsive to the ESD event are also responsive to a signal (22out: CPD) to that detects the absence of a power supply voltage (VDD, VDDE) of one of the domains and places those devices in a condition to disable the level shift circuit (205) if the power supply voltage is not present (VDD or VVDE).