LIN Driver Circuit Slew-Rate Control for EMI Tolerance
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Solution Overview
Problem
Line driver circuits for Local Interconnect Networks (LIN) face challenges in achieving high electromagnetic interference (EMI) tolerance while maintaining low manufacturing costs, as the use of high voltage capacitors for phase compensation decreases EMI tolerance and increases costs.
Innovation Solution
A LIN driver circuit design that eliminates the need for high voltage capacitors by using a signal generation circuit and a buffer amplifier to generate a linearly varying signal, coupled with a capacitor that enables the Miller effect, thereby controlling the slew rate independently of gate capacitance and preventing EMI noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high voltage capacitors are used for phase compensation, then phase compensation is achieved, but EMI tolerance decreases and manufacturing costs increase
Solution Approach 1:
The patent removes high voltage capacitors from the circuit by extracting their phase compensation function and implementing it through an alternative mechanism using a buffer amplifier and resistor network that generates the necessary linear voltage variation without requiring capacitive phase compensation
Solution Approach 2:
The patent replaces the electrical capacitor-based phase compensation mechanism with an amplifier-based voltage control mechanism that achieves the same effect through active circuit elements rather than passive capacitive components, thereby eliminating EMI susceptibility associated with capacitors
2Reliability
If high voltage capacitors are used for phase compensation, then phase compensation is achieved, but manufacturing costs increase
Solution Approach 1:
The patent extracts the phase compensation function from high voltage capacitors and implements it through standard circuit components (buffer amplifier, resistors) that are more readily available and less expensive, thereby reducing manufacturing costs while maintaining the required phase compensation performance
Solution Approach 2:
The patent replaces expensive high voltage capacitors with cheaper alternative components including standard resistors and buffer amplifier circuits that achieve the same functional result at lower cost, making the overall system more economically viable
3Productivity
If the output signal slope is increased to achieve higher bit rates, then data transmission speed improves, but EMI generation increases
Solution Approach 1:
The patent employs feedback mechanisms through the buffer amplifier and resistor network to precisely control the output signal slope, allowing optimization of the balance between transmission speed and EMI generation by adjusting feedback parameters rather than simply increasing signal amplitude
Solution Approach 2:
The patent changes the controlling parameter for signal slope from direct capacitor charging/discharging to amplifier-controlled voltage variation, allowing independent adjustment of slope characteristics to achieve optimal bit rate while minimizing EMI through precise parameter control
4Object-affected harmful factors
If the slew rate is controlled to reduce EMI, then EMI emission decreases, but data transmission capability may be compromised
Solution Approach 1:
The patent uses feedback control through the buffer amplifier to maintain the slew rate within optimal bounds that simultaneously reduce EMI emission and preserve data transmission capability, adjusting the feedback parameters to achieve the desired balance between these competing requirements
Solution Approach 2:
The patent changes the approach to slew rate control from passive capacitor-based timing to active amplifier-based control, allowing dynamic adjustment of the slew rate parameter to optimize both EMI reduction and data transmission performance through precise parameter management
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 EMI tolerance and reduces manufacturing costs by eliminating capacitive paths for EMI noise, allowing stable operation even without high voltage capacitors, and maintains correct data transmission across varying load conditions.
Implementation Method 1
a capacitor coupled between the first node and a feedback node of the driver circuit such that the Miller effect occurs at the capacitor and a slew rate for the drive signal is generated at the feedback node
Data Source
AI summary
A driver circuit and corresponding methods and systems are disclosed, the driver circuit comprises a signal generation circuit to generate a linearly varying signal at a first node based on a clock signal and an output transistor to receive the linearly varying signal and output a drive signal to a bus. A buffer amplifier is coupled between the first node and a gate of the output transistor to disable the gate capacitance of the output transistor. The driver circuit further comprises a capacitor coupled between the first node and a feedback node of the driver circuit such that the Miller effect occurs at the capacitor and a slew rate for the drive signal is generated at the feedback node.