Non-Linear LIN Transmitter Biasing for Timing and EMI Control
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Solution Overview
Problem
The Local Interconnect Network (LIN) protocol faces challenges in reliably transmitting data over serial buses due to variations in supply voltage, resistance, parasitic components, and electromagnetic interference, which affect the timing requirements for logic state transitions and lead to inefficiencies and increased power consumption.
Innovation Solution
A transmitter driver is developed using metal-oxide semiconductor field effect transistors (MOSFETs) or bipolar junction transistors (BJTs) with a current mirror circuit and amplifier to generate non-linear current waveforms for charging and discharging the serial bus, allowing for precise control of bit durations and reducing electromagnetic interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a LIN transmitter uses traditional linear biasing for logic state transitions, then the circuit is simple to implement, but the transmitter cannot reliably meet timing requirements under varying supply voltage and bus cable conditions
Solution Approach 1:
The patent implements dynamic biasing where the transmitter adjusts its bias current based on detected bus conditions (cable length, supply voltage, EMI levels). The circuit transitions from static linear biasing to dynamic non-linear biasing, allowing the transmitter to optimize its performance for each specific operating condition, thereby resolving the contradiction between reliability and complexity.
Solution Approach 2:
The patent changes the biasing parameter from fixed linear values to variable non-linear values that adapt to bus conditions. By modifying the bias current magnitude and waveform shape dynamically, the transmitter achieves reliable timing compliance across different cable lengths and supply voltages without requiring overly complex control circuits.
2Reliability
If a LIN transmitter uses fast logic state transitions to meet timing requirements, then timing compliance is achieved, but electromagnetic interference increases
Solution Approach 1:
The patent employs periodic pulse generation with controlled duty cycles to achieve logic state transitions. By using shaped pulses with optimized rise and fall times rather than abrupt transitions, the transmitter meets timing requirements while reducing high-frequency spectral content that causes EMI. The periodic nature of the communication protocol allows for consistent pulse shaping.
Solution Approach 2:
The transmitter dynamically adjusts its transition characteristics based on detected EMI conditions. When high EMI is detected, the circuit modifies its biasing to produce smoother transitions with reduced high-frequency components, thereby maintaining timing compliance while minimizing electromagnetic interference generation.
3Reliability
If a LIN transmitter uses high current draw to ensure reliable signal detection, then signal reliability improves, but power consumption increases
Solution Approach 1:
The patent implements variable current parameter adjustment where the transmitter uses higher current only when necessary (detected through bus conditions) and reduces current during normal operation. The non-linear biasing circuit dynamically scales the drive current based on cable length and supply voltage measurements, achieving reliable signal detection while minimizing overall power consumption.
Solution Approach 2:
The transmitter applies partial over-driving only when bus conditions require it (such as long cable lengths or low supply voltage), rather than maintaining excessive current continuously. This allows the system to achieve sufficient signal levels for reliable detection only when needed, reducing unnecessary power consumption during normal operating conditions.
4Object-generated harmful factors
If a LIN transmitter uses slow logic state transitions to reduce electromagnetic interference, then EMI decreases, but timing requirements may not be met
Solution Approach 1:
The patent employs parameter optimization where the biasing circuit adjusts transition speed parameters based on detected bus conditions. The non-linear biasing provides faster transitions when needed for timing compliance while incorporating shaping elements that suppress high-frequency components, achieving a balance between speed and EMI reduction through dynamic parameter adjustment.
Solution Approach 2:
The transmitter dynamically adjusts its transition characteristics based on real-time bus condition detection. When timing margins are tight, the circuit increases transition speed while using pulse shaping to control EMI. When timing margins are sufficient, the circuit slows transitions to reduce EMI, creating a dynamic balance between timing compliance and electromagnetic interference generation.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution enhances the reliability and power efficiency of LIN bus transmissions by accurately controlling rise and fall times, reducing electromagnetic interference, and maintaining consistent performance across varying load conditions.
Implementation Method 1
A transmitter driver is developed using metal-oxide semiconductor field effect transistors (MOSFETs) or bipolar junction transistors (BJTs) with a current mirror circuit and amplifier to generate non-linear current waveforms for charging and discharging the serial bus
Implementation Method 2
with a current mirror circuit and amplifier to generate non-linear current waveforms
Data Source
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AI summary
Described embodiments provide a transmitter for transmitting data over a serial bus coupled to the transmitter. The transmitter includes a controller to generate data for transmission by the transmitter. A transmit driver is coupled to the controller. The transmit driver, in response to the generated data for transmission, generates logic transitions on the serial bus. The transmit driver generates low-to-high logic transitions by charging the serial bus by a bus current based on a predetermined initial bias level for a first time period, and a first predetermined maximum bias level for a second time period. The transmit driver generates high-to-low logic transitions by discharging the serial bus by a bus current based on a pre-charged level of the transmit driver, and a second predetermined maximum bias level for a third time period.