Dual Mode CAN Termination Circuit for ASIL D Data Integrity
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Solution Overview
Problem
Existing solutions for protecting data integrity in automotive vehicle networks are inefficient and costly, particularly for applications requiring high safety integrity levels like ASIL D, as they often involve redundant hardware designs that increase overhead, die size, and power consumption.
Innovation Solution
A dual mode bus termination circuit optimized for both differential and single-ended communication modes on a CAN bus, which includes first and second resistance termination paths connected in parallel to match odd and even mode impedances, allowing a modified CAN transceiver to operate on a single wire in case of failure without performance loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If redundant hardware designs are used to protect data integrity in automotive vehicle networks, then reliability is improved, but device complexity increases
Solution Approach 1:
The termination circuit is designed to perform multiple functions: it provides impedance matching for both differential mode (120 ohms) and common mode (300 ohms) operations, and enables both normal two-wire communication and fallback single-wire communication. This multi-functionality eliminates the need for separate redundant hardware circuits, resolving the contradiction between reliability and device complexity.
2Reliability
If redundant hardware designs are used to protect data integrity, then reliability is improved, but die size increases
Solution Approach 1:
The patent merges the protection function into the existing termination circuit by adding a small number of components (resistors and capacitors) to the standard CAN termination. This integration approach allows the circuit to provide both normal operation and fault protection without requiring separate redundant hardware blocks, thereby maintaining compact die size while improving reliability.
3Reliability
If redundant hardware designs are used to protect data integrity, then reliability is improved, but power consumption increases
Solution Approach 1:
The circuit dynamically adapts its behavior based on fault detection. During normal operation, it functions as a standard termination circuit with minimal power consumption. Upon detecting a wire break or fault, it automatically reconfigures to enable single-wire communication mode, providing protection only when needed. This dynamic operation eliminates continuous power overhead associated with always-active redundant systems.
4Adaptability or versatility
If dual mode termination circuit is used, then adaptability is improved, but device complexity increases
Solution Approach 1:
The circuit achieves dual-mode functionality by changing impedance parameters rather than switching between completely different circuit topologies. By using specific resistor values (120 ohms for differential mode, 300 ohms for common mode) and adding simple RC elements, the same physical circuit adapts its electrical characteristics to match different communication modes, providing versatility without significant complexity increase.
Data Source
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AI summary
A Controller Area Network (CAN) system, method, and circuit are provided with a dual mode bus line termination circuit connected between signal lines of a serial bus and optimized for both differential and single-ended communication modes over the serial bus, where the dual mode bus line termination circuit includes first and second resistance termination paths connected in parallel between first and second bus wires of the serial bus to provide an odd mode termination impedance (RODD) that matches an impedance of the serial bus when operating in the differential communication mode, and to also provide an even mode termination impedance (REVEN) that matches an impedance of the serial bus when operating in the single-ended communication mode.