CAN Driver Module ESD Protection with Current Limiting
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Solution Overview
Problem
The use of common-mode chokes in CAN bus lines increases inductance, leading to energy storage during short circuits, which can damage ESD protection devices by causing them to enter the snapback region, as they are not fast enough to handle the resulting large currents and voltage peaks.
Innovation Solution
A CAN driver module with P-channel and N-channel MOSFETs, ESD protection components, load current sensing, and load current limiting components to control and restrict load currents, using diodes in parallel with snapback ESD protection elements to divert energy and prevent snapback mode activation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a common-mode choke is used with a CAN bus line to improve the electro-magnetic environment, then the electro-magnetic environment is improved, but the inductance of the CAN bus line increases causing large energy storage during short circuits
Solution Approach 1:
The patent implements current limiting components that proactively restrict the maximum current on CAN bus lines before short circuit events occur. By setting a current threshold below what would charge the inductance to dangerous energy levels, the system prevents the harmful energy storage from occurring in the first place, rather than trying to manage it after the fact
Solution Approach 2:
The patent accepts that common-mode chokes will increase inductance and energy storage, but converts this potentially harmful effect into a manageable parameter by designing ESD protection devices with breakdown voltages specifically calibrated to activate before the stored inductive energy becomes dangerous. The harmful inductance is thus transformed into a controlled design parameter
2Reliability
If ESD protection devices are designed to sustain very large ESD GUN stress currents (30A) through snapback protection, then they can handle ESD stress, but they are damaged by large currents from inductive short circuits
Solution Approach 1:
The patent places current limiting components in series with the CAN bus lines upstream of the ESD protection devices. These components continuously limit the maximum current to a safe level, preventing inductive short circuit currents from ever reaching the ESD devices and causing damage, while allowing normal ESD operation to proceed
Solution Approach 2:
The patent introduces current limiting components as intermediary elements between the CAN bus line and the ESD protection devices. These intermediaries selectively restrict current flow during abnormal inductive short circuit conditions while maintaining proper ESD protection functionality, acting as a protective mediator that distinguishes between harmful and beneficial current events
3Reliability
If complex clamp circuitry is used to sink current flowing through the inductance of the CAN bus line, then current sinking capability is improved, but the response speed is too slow to prevent damage to ESD protection devices
Solution Approach 1:
The patent implements current limiting components that continuously constrain the maximum current on the CAN bus line to a predetermined safe level. This preliminary action ensures that even during rapid inductive short circuit events with nanosecond rising edges, the current never exceeds what the simple ESD protection devices can handle, eliminating the need for complex slow-responding clamp circuitry
Solution Approach 2:
The patent extracts the complex clamp circuitry from the system and replaces it with simple current limiting components. By removing the need for complex current sinking circuitry and instead preventing excessive current from occurring in the first place through upstream current limiting, the system achieves both simplicity and fast response capability
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 effectively limits energy storage during short circuits, allowing safe dissipation of energy without damaging ESD protection devices and eliminating the need for complex clamp circuits, ensuring robustness against high ESD stress currents.
Implementation Method 1
the second ESD protection element is arranged such that reverse breakdown occurs in the second diode
Data Source
Figure 1~2
Figure 3~4
AI summary
An integrated circuit device comprising at least one controller area network, CAN, driver module comprising at least one driver component. The at least one driver component comprises at least one control input arranged to receive at least one control signal, and at least one output operably coupled to at least one CAN bus line and arranged to controllably output a load current based at least partly on the received at least one control signal. The integrated circuit device further comprises at least one electrostatic discharge, ESD, protection component operably coupled to the at least one CAN bus line. The at least one CAN driver module further comprises at least one load current sensing component arranged to sense the load current output by the at least one driver component and to generate at least one load current signal comprising an indication of the load current output by the at least one driver component, and at least one load current limiting component arranged to receive the at least one load current signal generated by the at least one load current sensing component and to cause the at least one driver component to at least partially restrict the load current output thereby if the at least one load current signal that indicates the load current exceeds a threshold. The at least one ESD protection component comprises at least one ESD protection element comprising snapback properties and at least one non-snapback protection element operably coupled in parallel across the at least one ESD protection element; the at least one non-snapback protection element comprising a breakdown voltage less than a breakdown voltage of the at least one ESD protection element.