CAN Receiver Circuit for Ultra-Wide Common-Mode Voltage Range
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Solution Overview
Problem
Conventional CAN bus receiving circuits have limitations in their common-mode input voltage range, which are not sufficient for modern vehicular environments with increased ground voltage shifts, and they often result in electromagnetic emission due to high-frequency fluctuations.
Innovation Solution
A receiving circuit with an ultra-wide common-mode input voltage range, comprising a resistor assembly, a reference amplifier, a first input amplifier assembly, a second input amplifier assembly, and an analog adder, which can handle differential signals between positive and negative infinite volts, and maintains low electromagnetic emission even when circuit parameters deviate from ideal values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional differential receiving circuits are used, then the circuit structure is simple, but the common-mode input voltage range is limited
Solution Approach 1:
The receiving circuit is divided into multiple independent amplifier assemblies (first input amplifier assembly and second input amplifier assembly), each handling different aspects of signal processing. This segmentation allows each module to be optimized independently, enabling the circuit to accept a wide common-mode voltage range while maintaining manageable complexity through modular design.
Solution Approach 2:
The amplifier assemblies are designed to perform multiple functions: they amplify differential signals, reject common-mode signals, and maintain stability across varying voltage conditions. This multi-functionality allows a single modular unit to handle various signal conditions, expanding the overall voltage range capability without proportionally increasing complexity.
2Adaptability or versatility
If resistor assembly is used to attenuate common-mode signals, then the voltage range is extended, but electromagnetic emission increases due to high-frequency fluctuations
Solution Approach 1:
The circuit employs feedback mechanisms within the amplifier assemblies to actively suppress common-mode signals and stabilize the differential signal amplification. This feedback control prevents the high-frequency fluctuations that would otherwise generate electromagnetic emission, while still maintaining the extended voltage range capability through proper signal conditioning.
Solution Approach 2:
The amplifier assemblies act as intermediary elements between the resistor assembly and the rest of the receiving circuit. They condition the attenuated signals from the resistor assembly, filtering out high-frequency components that cause electromagnetic emission while preserving the useful signal information, thus mediating between voltage extension and emission control.
3Adaptability or versatility
If the common-mode voltage is allowed to fluctuate, then the input voltage range is increased, but electromagnetic waves are emitted interfering with other vehicle functions
Solution Approach 1:
The differential amplifier structure with feedback mechanisms continuously monitors and maintains the relationship between differential and common-mode signals. This feedback ensures that while the circuit can accept a wide input voltage range, the common-mode voltage remains stabilized and does not fluctuate into ranges that would generate harmful electromagnetic waves affecting other vehicle systems.
Data Source
AI summary
A receiving circuit with an ultra-wide common-mode input voltage range applies to a controller area network (CAN) and comprises a resistor assembly electrically connected with a CANH and a CANL, a reference amplifier, a first input amplifier assembly, a second input amplifier assembly, and an analog adder. The receiving circuit receives voltages from the CANH and CANL. The resistor assembly bucks voltage, respectively generating CANH and CANL voltage divisions at first and second nodes and outputting the voltage divisions to the first and second input amplifier assemblies. The first and second input amplifier assemblies amplify the differential signal between the first and second nodes and convert the differential signal into single-end signals. The analog adder adds the single-end signals as the output signal. The receiving circuit can receive the signal ranging between the maximum and minimum common-mode voltages and reduce electromagnetic emission.