Nonlinear LIN Transmit Biasing for Fast, Low-EMI Bus Transitions
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Solution Overview
Problem
The Local Interconnect Network (LIN) protocol faces challenges in maintaining reliable and efficient communication due to variations in supply voltage, resistance, parasitic components, and electromagnetic interference, which affect the ability of LIN transmitters to meet timing requirements for logic state transitions.
Innovation Solution
A transmitter with a controller and a transmit driver that generates logic transitions on a serial bus by charging and discharging the bus based on predetermined bias levels and time periods, using output transistors such as MOSFETs or BJTs, and includes calibration to estimate parasitic components, allowing for efficient and reliable communication.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a LIN transmitter uses fixed current levels for logic state transitions, then the circuit is simple, but the transmitter cannot meet timing requirements under varying bus conditions (long cables with high resistance/parasitics vs. short cables with low resistance/parasitics)
Solution Approach 1:
The transmitter dynamically adjusts bias current levels based on detected bus conditions. The system transitions from fixed current levels to variable current levels that adapt to the actual bus characteristics (resistance, parasitic components, cable length), allowing the same transmitter circuit to optimize performance across different operating conditions without requiring multiple hardware configurations
Solution Approach 2:
The transmitter changes operational parameters (bias current levels) based on detected bus conditions. By measuring bus characteristics and adjusting current parameters accordingly, the system achieves adaptability to varying conditions while maintaining a relatively simple circuit architecture that can operate across multiple parameter states
2Speed
If a LIN transmitter uses fast logic state transitions, then communication speed is improved, but electromagnetic interference increases
Solution Approach 1:
The transmitter uses controlled periodic current adjustments during logic state transitions. Instead of abrupt current changes that cause EMI, the system applies current in controlled stages or periods, allowing the bus to charge/discharge in a manner that achieves required transition speeds while limiting electromagnetic interference through controlled current profiles
Solution Approach 2:
The transmitter dynamically changes current parameters during logic state transitions to balance speed and EMI. By adjusting bias current levels and transition current profiles based on bus conditions, the system achieves fast transitions when necessary while reducing current sweep rates or peak currents to minimize electromagnetic interference
3Reliability
If a LIN transmitter operates with high current draw, then logic state transitions are reliable, but power consumption increases
Solution Approach 1:
The transmitter adjusts bias current parameters based on detected bus conditions to achieve reliable logic state transitions with minimum necessary power. By measuring bus characteristics (resistance, parasitics, cable length) and calculating optimal current levels, the system maintains reliable transitions while avoiding excessive current draw that would waste power, adapting parameters to match actual bus requirements
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 enables reliable and power-efficient data transmission over LIN buses, reducing electromagnetic interference and improving communication accuracy across varying conditions.
Implementation Method 1
The transmit driver generates low-to-high logic transitions on the serial bus by charging the serial bus by a bus current based on (i) a predetermined initial bias level for a first time period, and (ii) a first predetermined maximum bias level for a second time period
Implementation Method 2
The transmit driver generates high-to-low logic transitions on the serial bus by discharging the serial bus by a bus current based on (i) a pre-charged level of the transmit driver, and (ii) a second predetermined maximum bias level for a third time period
Data Source
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 on the serial bus by charging the serial bus by a bus current based on (i) a predetermined initial bias level for a first time period, and (ii) a first predetermined maximum bias level for a second time period. The transmit driver generates high-to-low logic transitions on the serial bus by discharging the serial bus by a bus current based on (i) a pre-charged level of the transmit driver, and (ii) a second predetermined maximum bias level for a third time period.