CAN Transmitter Circuit With OTA Ringing Suppression
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Solution Overview
Problem
The ringing phenomenon in Controller Area Network (CAN) bus communication, caused by impedance mismatches and leading to signal corruption and communication failures, is exacerbated by increasing baud rates and network size, necessitating a novel ringing suppression circuit to maintain signal integrity and improve data rates.
Innovation Solution
A modified transmitter circuit with two operational transconductance amplifiers (OTAs) is employed to actively pull CAN high and low voltage signals to a common mode voltage during state transitions, suppressing ringing and improving impedance matching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If impedance matching is not implemented, then device complexity is reduced, but signal integrity deteriorates due to ringing phenomenon
Solution Approach 1:
The transmitter circuit proactively detects when a dominant-to-recessive transition is occurring and preemptively adjusts the output impedance by enabling the impedance matching circuit before the ringing can significantly corrupt the signal. This preliminary action prevents the harmful effect rather than correcting it afterward.
Solution Approach 2:
The impedance matching circuit dynamically adjusts the output impedance of the transmitter by controlling the switching elements (MOSFETs or transistors) to create a temporary low-impedance path to ground during dominant-to-recessive transitions. This dynamic adjustment is controlled by the transition detection circuit that monitors the differential voltage.
2Productivity
If baud rate is increased, then productivity is improved, but signal integrity deteriorates due to exacerbated ringing
Solution Approach 1:
The impedance matching circuit applies a counteracting force to the ringing phenomenon by creating a damping effect through the temporary low-impedance path. This preliminary anti-action suppresses the oscillations that would otherwise be exacerbated by high baud rates, allowing faster data transmission without proportional increase in signal corruption.
3Adaptability or versatility
If network size is increased, then adaptability is improved, but signal integrity deteriorates due to increased ringing
Solution Approach 1:
The impedance matching circuit applies localized quality adjustment at the transmitter output stage, creating a controlled low-impedance region specifically during transition periods. This local intervention addresses the ringing problem at its source without requiring global network modifications, enabling the network to scale while maintaining signal integrity.
Data Source
AI summary
A transmitter circuit with ringing suppression applicable to a controller area network bus is provided, which includes a CAN bus driver stage receiving a transmit data signal and generating a CAN high voltage signal and a CAN low voltage signal, a first operational transconductance amplifier electrically connected with the CAN bus driver stage for receiving the CAN high voltage signal, and a second operational transconductance amplifier electrically connected with the CAN bus driver stage for receiving the CAN low voltage signal. A common mode voltage of a dominant state as well as a control signal are applied such that when the control signal is logically high, the first and second operational transconductance amplifiers actively pulls the CAN high voltage signal and the CAN low voltage signal to be equal to the common mode voltage of the dominant state so as to suppress ringing phenomenon occurring in the CAN bus.