Output Circuit Rise/Fall Randomization for EMI Noise Reduction
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Solution Overview
Problem
Conventional semiconductor integrated circuits with constant rise and fall times of output signals generate specific frequency components that cause electromagnetic radiation noise, interfering with reference clocks in applications like tuners and imaging systems.
Innovation Solution
Incorporating a random number generation circuit and control registers to variably control the rise and fall times of output signals based on randomly generated data, distributing these times to reduce electromagnetic radiation noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the rise and fall times of the output signal are made constant, then the output circuit design is simplified, but electromagnetic radiation noise is generated due to specific frequency components
Solution Approach 1:
The patent applies dynamics by making the rise and fall times of the output signal variable rather than constant. A control circuit dynamically adjusts these timing parameters based on stored control data, transforming the static output signal characteristics into dynamic ones. This eliminates fixed frequency components while maintaining circuit simplicity, thereby reducing electromagnetic radiation noise without significantly increasing device complexity.
2Ease of operation
If the rise and fall slopes of the output signal are made constant, then the output circuit control is simplified, but reference clocks are influenced by electromagnetic radiation noise
Solution Approach 1:
The patent makes the output signal characteristics dynamic by varying rise and fall times according to stored control data. This dynamic adjustment prevents the generation of consistent electromagnetic radiation patterns that would interfere with reference clocks, thereby improving reliability while keeping the control mechanism simple through pre-stored control sequences.
Solution Approach 2:
The patent changes the temporal parameters of the output signal by varying rise and fall times based on stored control data. This parameter variation disrupts the formation of specific frequency components, reducing electromagnetic radiation noise that would otherwise affect reference clock stability, while maintaining ease of operation through programmable control.
3Object-generated harmful factors
If variable rise and fall times are implemented, then electromagnetic radiation noise is reduced, but the device complexity increases
Solution Approach 1:
The patent segments the control function by separating the random number generation, control data storage, and output signal generation into distinct functional blocks. This modular segmentation allows the variable rise and fall time control to be implemented without requiring a complete redesign of the entire circuit, thereby reducing the impact on overall device complexity while effectively reducing electromagnetic radiation noise.
4Reliability
If variable rise and fall times are implemented, then reference clock interference is minimized, but the control mechanism becomes more complex
Solution Approach 1:
The control mechanism is segmented into modular functional blocks including random number generation, control data storage in registers, and output signal generation. This segmentation allows the variable rise and fall time control to protect reference clocks from interference while keeping each control component relatively simple and manageable, preventing excessive overall complexity.
Data Source
AI summary
The invention reduces unnecessary electromagnetic radiation noise associated with a step pulse of an output signal. A random number control register is a register for controlling start, standby, stop, timing or the like of output of random number data from a random number generation circuit. Random number data outputted by the random number generation circuit is stored in a rise/fall time variable data register. The data stored in the rise/fall time variable data register is replaced by random number data sequentially generated by the random number generation circuit. An output circuit is a circuit for outputting a signal from an internal circuit of a microcomputer to an external device, and the rise/fall times of the output signal from the output circuit are variably controlled in response to the random number data stored in the rise/fall time variable data register.