Differential Transmission Circuit for CAN-FD Ringing Suppression
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Solution Overview
Problem
Conventional methods for suppressing ringing in high-speed CAN-FD communication systems increase radiation noise by doubling the differential signal amplitude, which is not effectively managed.
Innovation Solution
A transmission circuit with a first and second transmitter, where the second transmitter outputs a differential signal with a smaller amplitude and reverse polarity during the recessive period, maintaining low impedance and reducing ringing and radiation noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a drive method is used to suppress ringing in high-speed CAN-FD communication, then ringing is suppressed, but the amplitude of the differential signal doubles, increasing radiation noise
Solution Approach 1:
The patent inverts the conventional approach by using a non-drive state during the dominant period instead of a drive state. This reversal maintains low impedance to suppress ringing while avoiding the amplitude doubling that causes radiation noise. The second transmitter outputs a differential signal with smaller amplitude and reverse polarity during recessive period, and both transmitters coordinate their drive/non-drive states to achieve impedance control without excessive signal amplitude.
Solution Approach 2:
The patent changes the impedance parameter dynamically by switching between drive and non-drive states of the transmitters. During the dominant period, the system transitions to a low impedance state by using non-drive states, and during the recessive period, it uses drive states. This parameter change allows ringing suppression while controlling radiation noise through coordinated transmitter operation.
2Reliability
If the impedance of the transmission line is lowered to suppress ringing, then ringing is reduced, but the amplitude of the differential signal increases, causing more radiation noise
Solution Approach 1:
The patent inverts the conventional approach by using a non-drive state during the dominant period instead of a drive state. This reversal maintains low impedance to suppress ringing while avoiding the amplitude doubling that causes radiation noise. The second transmitter outputs a differential signal with smaller amplitude and reverse polarity during recessive period, and both transmitters coordinate their drive/non-drive states to achieve impedance control without excessive signal amplitude.
Solution Approach 2:
The patent changes the impedance parameter dynamically by switching between drive and non-drive states of the transmitters. During the dominant period, the system transitions to a low impedance state by using non-drive states, and during the recessive period, it uses drive states. This parameter change allows ringing suppression while controlling radiation noise through coordinated transmitter operation.
Data Source
AI summary
A transmission circuit includes a first transmitter and a second transmitter. The first transmitter turns OFF first transistors when a transmission data is in a high level, and turns ON the first transistors when the transmission data is in a low level. When a permission signal is in the high level, the second transmitter turns ON the second transistors when the transmission data is in the high level, and turns OFF the second transistors when the transmission data is in the low level. Diodes are set to suppress an amplitude of a differential signal in an ON time of the second transistors more than an amplitude of a differential signal in an ON time of the first transistors, to suppress ringing and radiation noise.