ESD Protection Circuit with Stacked NMOS Transistors
Solution Overview
Problem
Conventional ESD protection circuits in integrated circuits face challenges with high snapback voltage and poor ESD performance due to high power dissipation, leading to potential damage from electrostatic discharge and transient conditions.
Innovation Solution
A discharging unit comprising two NMOS transistors in series, coupled with a discharging controller that includes an ESD connection unit and a voltage clamping unit, effectively manages ESD events by establishing control voltages to turn on and off the transistors, providing a robust discharge path while minimizing power dissipation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If stacked NMOS transistors are used for ESD protection, then robust ESD protection is provided, but snapback voltage increases and power dissipation increases
Solution Approach 1:
The ESD protection circuit is divided into multiple functional blocks: discharging unit with stacked NMOS transistors, discharging controller, ESD connection unit, and voltage clamping unit. Each block performs a specific function to manage the ESD event separately, allowing robust protection while controlling power dissipation through coordinated operation.
Solution Approach 2:
The circuit dynamically switches between normal operation mode and ESD protection mode. The discharging controller activates the discharging unit only during ESD events, and the voltage clamping unit dynamically adjusts voltages to turn on/off transistors as needed, minimizing power dissipation during normal operation while providing robust protection when needed.
2Reliability
If stacked NMOS transistors are used for ESD protection, then robust ESD protection is provided, but snapback voltage increases
Solution Approach 1:
The voltage clamping unit acts as an intermediary between the ESD pulse and the stacked NMOS transistors. It clamps the ESD pulse to establish a second control voltage that turns on the second transistor, preventing excessive voltage buildup and reducing snapback voltage effects while maintaining ESD protection capability.
Solution Approach 2:
The circuit changes voltage parameters dynamically during ESD events. The ESD connection unit establishes a first control voltage to turn on the first transistor, and the voltage clamping unit establishes a second control voltage to turn on the second transistor, optimizing the voltage parameters to reduce snapback voltage while maintaining protection.
3Speed
If discharging unit with two NMOS transistors is used, then fast and uniform discharge is achieved, but device complexity increases
Solution Approach 1:
The discharging unit is segmented into two NMOS transistors with distinct functions: the first transistor handles the initial ESD pulse response, and the second transistor provides continued discharge capability. This segmentation enables fast and uniform discharge while keeping each transistor's design relatively simple.
Solution Approach 2:
The stacked NMOS transistor configuration serves multiple functions: providing a discharge path for ESD events, protecting internal circuitry from excessive currents during normal operation, and enabling fast uniform discharge. This multi-functionality justifies the increased device complexity by delivering multiple benefits from a single structural arrangement.
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 enhances ESD protection by ensuring fast and uniform discharge of stress currents, reducing the risk of damage and improving circuit reliability by maintaining voltages within oxide breakdown limits, thereby improving ESD performance and preventing current leakage.
Implementation Method 1
the first capacitor is coupled to the first transistor, the gate of the first PMOS and the third gate at one end, and to the ground pad at another end. The first capacitor clamps the ESD pulse to establish a second control voltage to turn on the second NMOS transistor in the ESD event
Data Source
AI summary
An integrated circuit and a protection circuit capable of protecting electrostatic discharge (ESD) damage. The integrated circuit comprises a first pad, a ground pad, a second pad, a device circuitry, a discharging unit, and a discharging controller. The discharging unit comprises first and second transistors in series. The discharging controller comprises an ESD connection unit, and a voltage clamping unit. The ESD connection unit, coupled to the first pad and the discharging unit, receives an ESD pulse to establish a first control voltage to turn on the first transistor in the ESD event. The voltage clamping unit, coupled to the ESD connection unit and the first, second and ground pads, clamps the ESD pulse to establish a second control voltage to turn on the second transistor in the ESD event, and receives an operation voltage at the first pad to turn off the second transistor in normal operation.