Crystal Oscillator Switching Circuit for Fast Low-Energy Start-Up
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Solution Overview
Problem
Conventional Pierce oscillator circuits for generating RF signals, particularly in Bluetooth Low Energy (BLE) applications, face challenges with high energy consumption and sensitivity to parasitic capacitances, leading to inefficient start-up and increased circuit area.
Innovation Solution
A novel oscillator circuit design featuring a switching circuit that alternately connects the power source to the electrodes of a crystal during start-up, using extreme voltage detection to optimize oscillating signal amplitude, and transitions to a steady-state phase with a switched capacitor configuration to reduce power consumption and sensitivity to parasitic capacitances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If a conventional Pierce oscillator circuit is used, then the circuit can generate oscillating signals, but the start-up time and energy consumption are excessive
Solution Approach 1:
The patent applies preliminary action by detecting the oscillation state of the crystal before the oscillator fully starts up and proactively adjusting the capacitive loading. The extreme voltage detection unit identifies when the crystal oscillation amplitude reaches a threshold, triggering the switching circuit to adjust capacitor connections. This preliminary adjustment optimizes the start-up process, reducing both start-up time and energy consumption compared to conventional Pierce oscillators that passively wait for natural start-up.
2Reliability
If two capacitors are used in the Pierce oscillator, then the oscillation can be maintained, but the circuit area increases substantially
Solution Approach 1:
The patent merges the functions of multiple capacitors into a single capacitor with switching circuitry. Instead of using two separate capacitors as in the conventional Pierce oscillator, the invention uses one capacitor whose effective capacitance is dynamically adjusted by a switching circuit controlled by the extreme voltage detection unit. This merging approach maintains oscillation reliability while substantially reducing the circuit area occupied by capacitive components.
Solution Approach 2:
The patent applies dynamics by making the capacitive loading adjustable rather than fixed. The switching circuit dynamically changes the capacitor configuration based on the oscillation state detected by the extreme voltage detection unit. This dynamic adjustment allows the circuit to optimize performance during different operating phases (start-up and steady-state) while using fewer physical components, thereby reducing circuit area while maintaining reliable oscillation.
3Ease of operation
If the Pierce oscillator architecture is used, then the circuit can operate, but it is sensitive towards parasitic capacitances over the quartz crystal
Solution Approach 1:
The patent applies feedback by using the extreme voltage detection unit to continuously monitor the crystal oscillation amplitude and use this information to control the switching circuit. This feedback mechanism allows the system to detect when parasitic capacitances are affecting performance and adjust the capacitive loading accordingly. The feedback loop compensates for the harmful effects of parasitic capacitances, making the oscillator less sensitive to these unwanted electrical properties while maintaining ease of operation.
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 proposed oscillator circuit reduces start-up time and energy consumption, achieves lower power usage, and is less sensitive to parasitic capacitances, enabling more efficient generation of RF signals with reduced circuit area.
Implementation Method 1
The crystal may comprise a piezo-electric material such as e.g. quartz
Data Source
AI summary
The present document relates to oscillator circuits and a method. An oscillator circuit generates an oscillating voltage signal, wherein the crystal has a first electrode and a second electrode. The oscillator circuit has a power source with a supply terminal and a reference terminal. The oscillator circuit has a switching circuit arranged between the power source and the crystal. The switching circuit, in a start-up phase, alternately connects the supply terminal of the power source to the first and second electrode of the crystal such that an amplitude of the oscillating voltage signal is increased.