Differential Oscillator Trimming via Isolated Resistor Network
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Solution Overview
Problem
Oscillators often deviate from their intended frequency due to manufacturing tolerances and material impurities, requiring trimming that is challenging due to high sensitivity to parasitic capacitance and resistance, leading to increased noise and power consumption, and potential glitches in the output signal.
Innovation Solution
A trimmable resistor (RCAL) is used to adjust the resistance value, combined with one-hot encoding and symmetrical distribution, reducing parasitic effects and isolating trimming switches from sensitive nodes, allowing for low-power, glitch-free frequency tuning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If trimming switches are connected directly to sensitive nodes for frequency adjustment, then frequency tuning capability is improved, but parasitic capacitance and resistance increase leading to higher noise and power consumption
Solution Approach 1:
The patent introduces non-sensitive nodes as intermediary connection points between the trimming switches and the sensitive oscillating nodes. These intermediary nodes act as buffers that allow the trimming switches to adjust frequency without directly exposing the sensitive nodes to parasitic effects. The switches connect to intermediate nodes that are not part of the high-frequency oscillating circuit, thereby mediating the trimming function while isolating the sensitive nodes from harmful parasitic elements.
Solution Approach 2:
The patent segments the oscillator circuit into sensitive nodes (oscillating nodes) and non-sensitive nodes (intermediary nodes). By dividing the circuit topology into these separate segments, the trimming functionality is separated from the sensitive oscillating core. This segmentation allows independent optimization of each segment - the oscillating nodes maintain low parasitic characteristics while the trimming switches operate from isolated non-sensitive nodes.
2Measurement precision
If trimming switches are used for frequency adjustment, then frequency precision is improved, but glitches may appear in the output signal
Solution Approach 1:
The non-sensitive intermediary nodes serve as mediators that prevent direct interaction between the trimming switches and the oscillating signal path. When trimming switches change state to adjust frequency, the transition occurs at the isolated non-sensitive nodes rather than directly at the sensitive oscillating nodes. This intermediary buffering prevents switch transient effects from coupling into the output signal, thereby maintaining signal stability while achieving precise frequency control.
3Adaptability or versatility
If conventional trimming methods are used, then frequency adjustment is achieved, but noise and power consumption increase
Solution Approach 1:
By using non-sensitive nodes as intermediaries, the patent creates an isolated trimming subsystem that does not directly load the sensitive oscillating nodes. This reduces the power consumption associated with driving trimming components, as the intermediary nodes can be driven with lower power while still achieving the frequency adjustment effect. The isolation prevents power consumption in the trimming circuit from adding directly to the oscillator's power budget.
Data Source
AI summary
According to an aspect, there is provided a swing-boosted differential oscillator and a method for trimming the oscillator. The oscillator comprises a switch (110) for connecting a set of capacitors (C1, C2) alternately to power supply and ground (102, 112) based on a switching control (116A, 116B), a comparator (114) configured to produce the switching control (116A, 116B) by comparing a voltage of the capacitors (C1, C2) at the inputs (VC1, VC2) of the comparator to a preset threshold voltage, and a trimmable resistor (RCAL) connecting the inputs (VC1, VC2) of the comparator, the resistor controlling the frequency of the output (118) of the oscillator.