CAN Transceiver Differential Voltage Control for Bus Transition Stability
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Solution Overview
Problem
CAN transceivers experience signal reflection and oscillation during transitions between dominant and recessive frames, leading to increased bit error rates and reduced transmission reliability and efficiency.
Innovation Solution
The CAN transceiver controls the voltage difference between the high-side and low-side signals within specific threshold ranges by using a combination of power transistors and switches, adjusting the voltage levels based on the mode control signal and data transmission level to minimize signal interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the transmission rate of the CAN bus is reduced to avoid erroneous outputs, then the reliability of data reception is improved, but the signal transmission efficiency deteriorates
Solution Approach 1:
The patent changes the voltage difference parameter between high-side and low-side signals during transitions. Specifically, it controls the voltage difference to be within a first range (1.8V to 3.3V) when avoiding errors and within a second range (-300mV to 300mV) during normal operation, thereby resolving the contradiction between reliability and transmission efficiency
Solution Approach 2:
The patent dynamically adjusts the voltage difference parameter based on the state of the CAN bus. When detecting a transition from dominant to recessive frame, it applies a first voltage range; otherwise, it applies a second voltage range. This dynamic adjustment allows the system to maintain high reliability during critical transitions while preserving transmission efficiency during normal operation
2Reliability
If the voltage difference between high-side and low-side signals is increased to improve signal integrity, then the transmission reliability is improved, but the risk of signal oscillation and reflection increases
Solution Approach 1:
The patent precisely controls the voltage difference parameter within specific ranges. By limiting the voltage difference to 1.8V-3.3V during transitions and -300mV-300mV during normal operation, it achieves optimal balance between signal integrity and minimizing oscillation/reflection effects
Solution Approach 2:
The patent uses feedback control by monitoring the state of the CAN bus and adjusting the voltage difference accordingly. The control unit detects whether the bus is in transition state or normal state, and selectively applies appropriate voltage ranges, thereby preventing harmful oscillation and reflection while maintaining transmission reliability
Data Source
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AI summary
A CAN transceiver, including a data transmission port, control port, high-side bus port, and low-side bus port; when the mode control signal is in a first state and data transmission signal is at logic low level, a voltage difference between the high-side signal and low-side signal is between 1.8 V and 3.3 V; when the mode control signal is in the first state and data transmission signal is at logic high level, the voltage difference between the two is between -1.8 V to -3.3 V; when the mode control signal is in a second state and data transmission signal is at logic low level, the voltage difference between the two is between 1.8 V to 3.3 V; when the mode control signal is in the second state and data transmission signal is at logic high level, the voltage difference between the two is between -300 mV and 300 mV.