ESD Protecting Circuit With Dynamic Switch For Signal Swing
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Solution Overview
Problem
Existing ESD protecting circuits limit the signal swing to a range between VSS and VDD, restricting the operational flexibility and requiring additional masking for deep N-well structures, which increases costs.
Innovation Solution
An ESD protecting circuit design that includes a switch, such as a MOS transistor, controlled by an ESD detecting circuit to isolate the circuit from the internal circuit during normal conditions, allowing signal swing beyond VDD and VSS, and optionally utilizing a PMOS transistor to eliminate the need for a deep N-well mask.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional ESD protecting circuit is used, then the internal circuit is protected from ESD voltage, but the signal swing is limited to a range between VSS and VDD
Solution Approach 1:
The patent employs dynamic switching of the ESD protecting module using a control signal. When an ESD event is detected, the switch becomes conductive to activate protection; during normal operation, the switch is non-conductive to allow full signal swing. This dynamic activation resolves the contradiction by making the protection conditional rather than continuous.
Solution Approach 2:
The patent introduces a switch as an intermediary element between the ESD protecting module and the I/O pad. This switch acts as a mediator that can isolate or connect the protection circuit based on ESD detection status, enabling full signal swing during normal operation while providing protection when needed.
2Reliability
If a deep N-well mask is used in the ESD protecting circuit, then the circuit reliability is improved, but the manufacturing cost increases
Solution Approach 1:
The patent changes the transistor type parameter from NMOS to PMOS in the ESD protecting module. This parameter change eliminates the requirement for deep N-well mask while maintaining the ESD protection functionality, thereby reducing manufacturing complexity and cost.
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 allows for an unrestricted signal swing and eliminates the need for a deep N-well mask when using a PMOS transistor, enhancing operational flexibility and reducing costs by preventing unnecessary masking.
Implementation Method 1
a switch, comprising a first terminal coupled to the second terminal of the first ESD protecting module, comprising a second terminal coupled to the I/O pad, and comprising a control terminal for receiving a control signal
Data Source
AI summary
An ESD protecting circuit comprising: a first and a second voltage pad; an I/O pad; a first ESD protecting module, comprising a first terminal coupled to the first voltage pad, and comprising a second terminal; a switch, comprising a first terminal coupled to the second terminal of the first ESD protecting module, comprising a second terminal coupled to the I/O pad, and comprising a control terminal for receiving a control signal; a second ESD protecting module, comprising a first terminal coupled to the first terminal of the MOS transistor, and comprising a second terminal coupled to the second voltage pad; and an ESD detecting circuit, for detecting if an ESD voltage exists, for generating the control signal to control the MOS transistor to be conductive when an ESD voltage is detected and to control the MOS transistor to be nonconductive when the ESD voltage is not detected.