Oscillating Clock Adjustment for EMI-Safe Touch Display ICs
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Solution Overview
Problem
Oscillators in electronic devices, such as touch and display driver ICs, can cause electromagnetic interference when their clock signal frequencies overlap with wireless communication frequencies, leading to errors and reduced signal quality in devices like mobile phones.
Innovation Solution
An oscillating signal adjusting circuit and method that includes a frequency shift circuit and a spread spectrum control circuit, which adjust the clock signal frequency and perform spreading spectrum operations based on mode control signals with varying voltage levels during display and touch sensing periods to generate an internal clock signal, thereby reducing electromagnetic interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the oscillator provides a clock signal at a fixed frequency, then the display and touch functions operate reliably, but electromagnetic interference occurs when the frequency overlaps with wireless communication bands
Solution Approach 1:
The patent applies dynamics by making the clock signal frequency adjustable rather than fixed. The oscillator frequency is dynamically changed between a first frequency during display/touch operations and a second frequency during wireless communication, allowing the system to adapt to different operational modes and avoid electromagnetic interference while maintaining functional reliability
Solution Approach 2:
The patent changes the frequency parameter of the clock signal based on operational mode. By switching between different frequency values (first frequency for display/touch, second frequency for communication), the system resolves the contradiction between maintaining reliable operation and avoiding electromagnetic interference with wireless communications
2Object-affected harmful factors
If the oscillator frequency is shifted to avoid communication bands, then electromagnetic interference is reduced, but the clock signal may no longer synchronize with display and touch operations
Solution Approach 1:
The patent implements periodic action by alternating between two frequency states based on operational phase. During display and touch operations, the oscillator uses the first frequency to ensure proper synchronization, while during wireless communication phases, it switches to the second frequency to avoid interference. This periodic switching ensures both synchronization reliability and electromagnetic compatibility
Solution Approach 2:
The system dynamically adjusts the oscillator frequency based on the operational phase detected by the processor. This dynamic adaptation allows the clock signal to maintain proper synchronization with display and touch operations when needed, while avoiding electromagnetic interference during communication phases
3Object-affected harmful factors
If a frequency shift circuit and spread spectrum control circuit are added, then electromagnetic interference is reduced, but the circuit complexity increases
Solution Approach 1:
The patent achieves multi-functionality by integrating the frequency adjustment capability into the existing oscillator circuit used for both display/touch operations and wireless communication. The same oscillator circuit dynamically serves multiple functions by switching frequencies, avoiding the need for completely separate circuits for different operational modes
Solution Approach 2:
The processor detects the operational phase and controls the oscillator frequency accordingly, creating a feedback loop where the system monitors its own state and adjusts the clock frequency to maintain both functional reliability and electromagnetic compatibility without requiring complex external control circuits
Data Source
AI summary
An oscillating signal adjusting circuit is provided. The oscillating signal adjusting circuit is adapted to generate an internal clock signal of a touch and display driver integrated circuit and includes a frequency shift circuit and a spread spectrum control circuit. The frequency shift circuit acquires a first setting data indicated by a mode control signal, and determines whether to shift a frequency of the input clock signal according to the first setting data to generate a first output clock signal. The spread spectrum control circuit to acquires a second setting data indicated by the mode control signal, and determines whether to perform a spreading spectrum operation on the first output clock signal according to the second setting data to generate the internal clock signal. The mode control signal has a first voltage level in a display period and has a second voltage level in a touch sensing period.