ESD Protection Circuit with Slew Rate Detection
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Solution Overview
Problem
Existing ESD protection systems can cause damage to integrated circuits (ICs) either during an ESD event or when not needed, as they may shunt energy errantly during non-ESD excess signaling conditions, such as over-voltage stress testing or one-time programming.
Innovation Solution
An ESD protection system comprising a first signal node, a reverse breakdown device, a slew rate response circuit, and selectively switched conductive devices, where a controllable voltage source manages the switching to enable shunting only during ESD events, preventing interference during non-ESD conditions like over-voltage stress testing or one-time programming.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a reverse breakdown device is used to shunt energy during ESD events, then IC protection is improved, but damage to the IC may occur during non-ESD excess signaling conditions
Solution Approach 1:
The ESD protection circuit dynamically adjusts its state based on the detected signal characteristics. The slew rate response circuit monitors the rate of change of voltage at the signal node and selectively activates the shunt path only when a fast-rising ESD event is detected, rather than remaining statically active. This dynamic behavior allows the circuit to provide protection during ESD events while avoiding interference during non-ESD conditions.
Solution Approach 2:
The circuit changes its electrical parameters (conductivity state of the shunt path) based on the detected signal slew rate. When the slew rate exceeds a threshold indicating an ESD event, the shunt path conductivity increases to divert energy. When the slew rate is below the threshold during normal or excess signaling, the shunt path remains high-impedance. This parameter change enables selective protection without causing errant clamping.
2Reliability
If the ESD protection circuit remains active continuously, then IC protection is improved, but interference with non-ESD operations such as over-voltage stress testing or one-time programming occurs
Solution Approach 1:
The protection circuit transitions from a static always-active state to a dynamic state that responds to signal characteristics. The slew rate response circuit enables the shunt path only during fast-rising ESD events, allowing normal operations including over-voltage stress testing and one-time programming to proceed without interference while maintaining ESD protection capability.
Solution Approach 2:
The slew rate response circuit acts as an intermediary between the signal node and the shunt path. It monitors signal characteristics and controls the activation of the ESD protection circuit, serving as a gatekeeper that prevents inappropriate activation during non-ESD operations while enabling protection during actual ESD events.
3Power
If the shunt path is always conductive, then energy diversion during ESD events is improved, but false activation during slow-rising excess voltage signals occurs
Solution Approach 1:
The shunt path conductivity is made dynamic rather than static. The slew rate response circuit detects the rate of voltage change and selectively activates the shunt path only when a fast-rising edge characteristic of ESD events is detected. This dynamic activation prevents false triggering during slow-rising excess voltage signals while maintaining effective energy diversion during actual ESD events.
Solution Approach 2:
The circuit changes the conductivity parameter of the shunt path based on the detected slew rate. When the voltage change rate exceeds a threshold, the shunt path transitions to a low-impedance state for effective energy diversion. When the voltage change rate is below the threshold, the shunt path remains high-impedance to avoid false activation. This parameter change based on signal characteristics eliminates false ESD clamp activation.
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 system effectively protects ICs from ESD events while allowing non-ESD excess signaling conditions to occur without interference, ensuring the IC operates within its nominal parameters, thereby preventing unnecessary damage and facilitating testing and programming processes.
Implementation Method 1
a reverse breakdown device coupled to the first signal node
Implementation Method 2
ESD is the sudden flow of electricity between two objects as electrical charge transfers from one of the objects to the other
Data Source
AI summary
An ESD protection system including structure to operate an IC during nominal conditions, to protect the IC during an ESD event, and to allow the IC to operate during slow rising input node voltages that exceed nominal conditions.