CAN Transceiver Circuit for Low Bus Loading and Glitch Protection
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Solution Overview
Problem
Existing CAN transceivers face issues with high capacitive loading on the bus during recessive states, which slows down bus speed, and are vulnerable to high-voltage glitches that can damage components due to inadequate protection mechanisms.
Innovation Solution
Implementing a current source device and current mirror coupled with a Zener diode to clamp gate-to-source voltage and minimize capacitive loading by ensuring transistors are off during recessive states, reducing the need for additional protection circuits and large resistors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If transistors are kept on during recessive states to maintain bus connectivity, then bus reliability is improved, but capacitive loading increases and bus speed decreases
Solution Approach 1:
The transistor gate voltages are dynamically adjusted based on the bus state. During recessive states, the transistors are turned off by applying appropriate gate voltages to minimize capacitive loading and maximize bus speed. During dominant states, the transistors are turned on to enable signal transmission, thus adaptively optimizing both speed and reliability.
2Reliability
If protection circuits are added to protect against high-voltage glitches, then component reliability is improved, but device complexity increases
Solution Approach 1:
The transistor gates are directly connected to the bus lines, allowing them to self-adjust their voltage levels in response to voltage transients and glitches. This self-service mechanism provides inherent protection against high-voltage events without requiring external protection circuits, thus maintaining component reliability while minimizing device complexity.
Solution Approach 2:
The transistor gates act as intermediary elements between the bus and the internal circuitry. These gates naturally limit the voltage transferred to internal nodes, serving as a first line of defense against voltage transients and eliminating the need for additional protection components.
3Reliability
If large resistors are used to protect against voltage transients, then component reliability is improved, but device area increases
Solution Approach 1:
The transistor gates self-regulate voltage levels through their inherent electrical characteristics, eliminating the need for large protection resistors that would occupy significant device area. This self-service approach provides voltage transient protection while maintaining compact device dimensions.
4Reliability
If additional protection circuits are implemented, then reliability against high-voltage glitches is improved, but manufacturing cost increases
Solution Approach 1:
The transistors provide inherent protection against high-voltage glitches through their natural electrical characteristics, eliminating the need for additional protection circuits. This reduces the number of components required, simplifies manufacturing processes, and lowers overall production costs while maintaining reliability.
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 protects transistors from high-voltage glitches and minimizes capacitive loading, thereby enhancing bus speed and reducing component stress, without the need for complex over-voltage sense circuits or large resistors.
Implementation Method 1
coupled with a Zener diode to clamp gate-to-source voltage
Data Source
AI summary
A bus transceiver circuit including a current source device, a current mirror coupled to the current source device, and a first transistor having a first control input and first and second current terminals. The bus transceiver circuit also includes a second transistor having a second control input and third and fourth current terminals. The third current terminal is coupled to the first control input at a first node. The fourth current terminal is coupled to the current mirror. A resistor is coupled between the first current terminal and the first node.