Half Open-Loop LIN Transmitter for EMI and RF Immunity
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Solution Overview
Problem
Existing LIN transmitters face challenges in achieving balanced RF and EMI performance, as well as immunity to ISO2 and ISO3a pulses, with previous designs either exhibiting poor EMI characteristics or increased circuit complexity.
Innovation Solution
A 'half open-loop-controlled' LIN transmitter design incorporating a current mirror, multiple current sources, and a control circuit with specific control signals, including load current threshold and fast discharge signals, to manage RF and EMI performance while maintaining immunity to ISO pulses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a closed-loop-controlled transmitter is used, then EMI characteristics are improved, but immunity to RF deteriorates
Solution Approach 1:
The transmitter is segmented into two independent control paths: a closed-loop control path for EMI management and an open-loop control path for RF immunity. The control circuit generates separate control signals for different current sources, allowing independent optimization of each aspect without interference from feedback loops during RF pulse events.
Solution Approach 2:
Different control strategies are applied to different parts of the transmitter circuit. The first current source operates under closed-loop control for normal EMI-performance critical operations, while the second current source operates under open-loop control for RF immunity critical operations, allowing each region to have optimized characteristics.
2Reliability
If an open-loop-controlled transmitter is used, then immunity to RF is improved, but EMI characteristics deteriorate
Solution Approach 1:
The transmitter functionality is divided into separate operational domains: one handled by closed-loop control for EMI management and another by open-loop control for RF immunity. This segmentation allows both control modes to coexist and contribute their strengths to different aspects of transmitter performance.
Solution Approach 2:
The patent merges closed-loop and open-loop control structures into a single hybrid transmitter design. The control circuit integrates both control paths, allowing the system to leverage the EMI benefits of closed-loop control and the RF immunity benefits of open-loop control simultaneously.
3Reliability
If a DAC-controlled transmitter is used, then both RF and EMI performance are improved, but device complexity increases
Solution Approach 1:
The patent extracts the essential control functions needed for RF immunity and EMI performance from the complex DAC-controlled architecture. By using simpler current sources with direct control signals rather than full DAC control, the design achieves the necessary performance without the excessive complexity of complete digital-to-analog conversion control.
Solution Approach 2:
The design uses simpler, more straightforward control circuitry compared to DAC-based solutions. Rather than investing in complex digital control infrastructure, the patent employs direct control signal generation with current sources that can be easily switched and controlled, achieving comparable performance with less complex hardware.
Data Source
AI summary
An LIN transmitter includes a current mirror coupled to a transmit output node and a control circuit coupled to a transmit input node for controlling the current mirror with various load current control signals.