Feedback-Controlled XTAL Driver Duty Cycling for Standby Power
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Solution Overview
Problem
Portable electronic devices face high power consumption from crystal oscillators, especially during standby modes, which limits their battery life and functionality.
Innovation Solution
A low voltage crystal oscillator driver with feedback-controlled duty cycling that operates in the sub-threshold regime of MOS transistors, using a calibration scheme to adjust circuit properties and duty cycle the XTAL driver based on oscillation amplitude, allowing the XTAL to maintain a stable output clock while minimizing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a crystal oscillator is used to provide an accurate clock source, then timing accuracy is improved, but power consumption increases
Solution Approach 1:
The patent applies periodic action by duty-cycling the crystal oscillator driver, turning it on and off in periodic intervals. The oscillator is activated only when needed to refresh the timing reference, rather than running continuously. This periodic operation maintains timing accuracy while dramatically reducing average power consumption, especially during standby modes.
Solution Approach 2:
The patent changes the operating parameters of the crystal oscillator by adjusting the duty cycle ratio between active and standby states. By dynamically modifying the proportion of time the oscillator is active versus inactive, the system optimizes the balance between timing accuracy requirements and power consumption constraints.
2Stability of the object's composition
If the XTAL driver operates continuously to maintain stable oscillation, then clock stability is improved, but power consumption increases
Solution Approach 1:
The system uses periodic action by implementing duty-cycled operation of the XTAL driver. Instead of continuous operation, the driver is periodically activated to refresh the oscillation and then deactivated. This periodic refresh approach maintains sufficient clock stability for the application while dramatically reducing power consumption during extended standby periods.
Solution Approach 2:
The system employs self-service by using the accumulated timing information from previous oscillator operations to determine when the oscillator needs to be refreshed. The timing circuitry tracks the elapsed time and automatically reactivates the oscillator when the predetermined time threshold is reached, eliminating the need for continuous monitoring and control.
3Use of energy by moving object
If duty cycling is applied to reduce power consumption, then energy efficiency is improved, but clock stability may deteriorate
Solution Approach 1:
The patent implements feedback control by monitoring the oscillator output and using this information to regulate the duty cycling operation. The feedback mechanism ensures that the oscillator is reactivated at appropriate intervals to maintain stability while maximizing power savings. The system adjusts the duty cycle based on actual oscillator performance and system requirements.
Solution Approach 2:
The system applies partial action by activating the XTAL driver for only the minimum necessary duration to refresh the oscillation, rather than maintaining full continuous operation. This partial operation approach provides sufficient clock stability for the application's needs while achieving significant power consumption reductions during standby modes.
Data Source
AI summary
A low voltage crystal oscillator (XTAL) driver with feedback controlled duty cycling for ultra low power biases an amplifier for an XTAL in the sub-threshold operating regime. A feedback control scheme can be used to bias the amplifier for an XTAL biased in the sub-threshold operating regime. The amplifier of a XTAL oscillator can be duty cycled to save power, e.g., the XTAL driver can be turned off to save power when the amplitude of the XTAL oscillation reaches a maximum value in range; but be turned back on when the amplitude of the XTAL oscillation starts to decay, to maintain the oscillation before it stops. In addition or alternatively, a feedback control scheme to duty cycle the amplifier of a XTAL oscillator can be used to monitor the amplitude of the oscillation.