CAN Bus Ringing Suppression Using a Transconductance Amplifier
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Solution Overview
Problem
CAN bus ringing occurs due to characteristic impedance mismatching, causing current oscillations between parasitic inductance and capacitance, particularly during waveform transitions.
Innovation Solution
A circuit comprising processing circuitry, a transconductance amplifier, and drivers to generate a CAN control signal, source/sink current based on the difference between input signals, and use exponential and hyperbolic functions to suppress ringing by destructively interfering with current oscillations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If characteristic impedance matching is not implemented, then device complexity is reduced, but current oscillations and ringing occur on the CAN bus
Solution Approach 1:
The patent introduces a transconductance amplifier as an intermediary component between the processing circuitry and the CAN bus. This amplifier acts as a mediator that transforms voltage signals into current signals, enabling active cancellation of ringing without requiring complex impedance matching networks. The intermediary device simplifies the overall system while eliminating the harmful ringing effect.
Solution Approach 2:
The patent applies preliminary anti-action by generating a counter-phase current signal through the transconductance amplifier that destructively interferes with the ringing oscillations before they propagate through the CAN bus. The exponential and hyperbolic function circuits pre-calculate and prepare the canceling current in advance, opposing the harmful ringing effect proactively rather than reactively.
2Adaptability or versatility
If exponential and hyperbolic function circuits are added, then signal processing capability is improved, but device complexity increases
Solution Approach 1:
The patent merges the exponential function circuit and hyperbolic function circuit into a unified transconductance amplifier architecture. By combining these functions within a single integrated amplifier stage, the patent achieves enhanced signal processing capability while minimizing the increase in device complexity. The merged design allows both functions to work synergistically rather than as separate additive components.
3Reliability
If transconductance amplifier with gain control is used, then ringing suppression effectiveness is improved, but power consumption increases
Solution Approach 1:
The patent implements dynamic gain control in the transconductance amplifier, allowing the gain to be adjusted based on the actual ringing conditions on the CAN bus. Rather than maintaining maximum gain continuously, the system dynamically adapts the amplification level to match the severity of the ringing, thereby improving suppression effectiveness when needed while reducing power consumption during normal operation. This dynamic adjustment optimizes the trade-off between reliability and energy usage.
Data Source
AI summary
A circuit to suppress ringing in a Controller Area Network (CAN) bus having a CAN high (CANH) wire and a CAN low (CANL) wire is provided. The circuit may include processing circuitry to generate a CAN control signal, and a transconductance amplifier to receive a first input signal corresponding to the CAN control signal and a voltage signal from the CANL wire, and to generate an output current signal based on a difference between the first input signal and the voltage signal from the CANL wire. An output terminal of the transconductance amplifier may be coupled to the CANH wire to source current to or sink current from the CANH wire.