LIN Transceiver Noise Suppression Circuit Using Saturation Bias
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Solution Overview
Problem
Switching noise generated by integrated switching circuitry in LIN transceivers can couple to the LIN bus and radiate as electromagnetic noise, degrading the performance of other circuits in automotive systems, particularly when the LIN bus is in a dominant state, and existing solutions require separating the ground of the transceiver from the switching circuitry.
Innovation Solution
A noise suppression circuit within the LIN transceiver that includes a switchable transistor and an amplifier, configured to operate in saturation mode when the bus is in a dominant state, providing a high AC output impedance to suppress switching noise frequencies above the switching frequency, without separating the ground of the transceiver from the switching circuitry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the LIN transceiver integrates switching circuitry on the same chip, then functionality and integration are improved, but switching noise is generated that couples through common ground and degrades LIN bus performance
Solution Approach 1:
The patent segments the ground path by introducing a separate ground connection for the switchable transistor that is electrically isolated from the common ground used by switching circuitry. This segmentation prevents noise coupling while maintaining integration benefits.
Solution Approach 2:
The patent introduces an intermediary ground connection specifically for the switchable transistor that acts as a mediator between the transistor and the common ground. This intermediary path isolates the transistor from switching noise while still allowing it to function within the integrated circuit.
2Object-generated harmful factors
If ground separation is implemented to suppress noise, then noise propagation is reduced, but device complexity and layout requirements increase
Solution Approach 1:
The patent applies local quality by providing a dedicated ground connection specifically for the switchable transistor's source terminal, while other components continue to use the common ground. This localized ground separation targets only the noise-sensitive path without requiring complete ground isolation.
Solution Approach 2:
The patent implements partial ground separation by isolating only the critical ground path for the switchable transistor from switching noise, rather than separating all ground connections. This partial action achieves sufficient noise suppression without excessive complexity.
3Reliability
If the switchable transistor operates in triode region, then AC output impedance is low which is good for signal driving, but switching noise frequencies are not suppressed
Solution Approach 1:
The patent makes the transistor's operating region dynamic by using a feedback mechanism that adjusts the gate voltage to maintain the transistor at the edge of saturation. This dynamic operation allows the transistor to provide noise suppression while maintaining adequate signal driving capability through adaptive biasing.
Solution Approach 2:
The patent changes the operating parameters of the switchable transistor by biasing it at the edge of saturation rather than deep in the triode region. This parameter change increases AC output impedance to suppress noise frequencies while maintaining sufficient signal driving capability through optimized bias conditions.
Data Source
AI summary
A noise suppression circuit comprises a switchable transistor and an amplifier having a first amplifier input terminal electrically coupled to an output terminal of the switchable transistor for sensing a voltage thereat, and an amplifier output terminal electrically coupled to a control terminal of the switchable transistor for outputting a control voltage thereto. The amplifier is configured, based on the sensed voltage and a transition mode threshold voltage of the switchable transistor which defines a boundary between operation modes of the switchable transistor, to set the voltage at the transistor output terminal to at least the transition mode threshold voltage such that for noise frequencies below or corresponding to the switching frequency of the switchable transistor a resistive path is provided between the transistor output terminal and the transistor reference terminal and for noise frequencies above the switching frequency of the switchable transistor the resistive path is substantially interrupted.