Display Driver IC Oscillator Scatter for EMI and Frequency Stability
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Solution Overview
Problem
Mobile electronic devices face signal quality deterioration due to electromagnetic interference (EMI) noise generated by the increased operating frequency of components, particularly in display driver ICs, which can be exacerbated by temperature and voltage changes, leading to deviations from target frequencies.
Innovation Solution
The display driver IC incorporates an oscillator scatter that generates a modified trim code by applying periodic positive and negative offsets to the oscillator clock, scattering the noise spectrum while maintaining the target frequency, and includes a frequency compensating block to adjust the operating frequency in response to temperature and voltage changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the operating frequency of components is increased to meet consumer demands for multi-functionality and compactness, then productivity and functionality are improved, but electromagnetic interference noise is generated which deteriorates signal quality
Solution Approach 1:
The patent applies periodic action by modulating the oscillator frequency around a center frequency using periodic frequency offset values. The frequency control block periodically adjusts the oscillator frequency based on pre-determined offset patterns, creating a frequency-modulated signal that disperses electromagnetic energy across multiple frequencies rather than concentrating it at a single frequency, thereby reducing EMI peak values
Solution Approach 2:
The patent implements parameter changes by dynamically varying the oscillator frequency parameter around a center frequency. The frequency control block changes the frequency parameter using pre-stored offset values from a look-up table, allowing the system to operate at multiple frequency points instead of a fixed frequency, which effectively reduces electromagnetic interference while maintaining functional performance
2Ease of operation
If a fixed frequency is used for the oscillator to simplify operation, then ease of operation is improved, but frequency deviation occurs due to temperature and voltage changes which deteriorates reliability
Solution Approach 1:
The patent implements feedback mechanisms through frequency calibration blocks that measure the actual oscillator frequency and generate compensation values. The system continuously monitors frequency deviations caused by temperature and voltage variations and applies corrective offset values to maintain the center frequency, creating a closed-loop control system that ensures frequency stability without complicating operation
Solution Approach 2:
The patent applies preliminary action by pre-calculating and storing frequency offset compensation values in a look-up table before operation. The frequency control block retrieves pre-determined offset values based on measured frequency deviations, allowing the system to compensate for temperature and voltage variations without real-time complex calculations, thus maintaining frequency stability while keeping the operation simple
3Device complexity
If frequency multiples are used for IP blocks to simplify design, then device complexity is reduced, but noise interference on peripheral components increases which deteriorates signal quality
Solution Approach 1:
The patent uses periodic action to modulate the oscillator frequency around a center frequency using periodic offset patterns. This frequency modulation disperses the spectral energy of frequency multiples across a broader frequency range, reducing the peak noise intensity at any single frequency while maintaining the simplified frequency design for IP blocks
Solution Approach 2:
The patent applies local quality by selectively applying frequency offsets to specific frequency bands where noise interference is most problematic. The frequency control block adjusts the oscillator frequency to avoid creating strong noise peaks at frequencies that would interfere with peripheral components, while maintaining simple frequency design for the IP blocks themselves
Data Source
AI summary
A display driver IC includes a register map, an oscillator, a timing controller, an oscillator scatter, and an intellectual property (IP) block. The register map is configured to store a trim code of a fixed frequency and scatter option information. The oscillator is configured to generate an oscillator clock based on the trim code. The timing controller is configured to generate an internal synchronization signal based on the oscillator clock. The oscillator scatter is configured to output a modified trim code to the oscillator based on the trim code, the scatter option information, and the internal synchronization signal. The intellectual property (IP) block is configured to receive a modified oscillator clock generated in the oscillator based on the modified trim code.