Crystal Oscillator Drive-Level Tuning for Reliable Start-Up
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Solution Overview
Problem
Existing crystal oscillator startup methods require complex and power-consuming circuits to monitor and control bias currents, leading to elevated power consumption and potential damage to crystals due to high drive levels.
Innovation Solution
A method involving a crystal oscillator connected to a non-volatile memory, where a parameter controlling the drive level is set to a high start-up value, then monotonically reduced while monitoring the oscillator, with a safety margin determined to ensure regular operation without overdriving, using a processing unit and counters to assess and adjust the drive level.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a high bias current is used to ensure reliable oscillator start-up, then the oscillator begins to oscillate reliably, but the crystal may be damaged by overdriving and power consumption increases
Solution Approach 1:
The patent applies preliminary action by setting the bias current to a high start-up value before the oscillator begins oscillating, ensuring reliable start-up. After a predetermined time delay allowing the oscillator to stabilize, the bias current is then reduced to a lower operating value. This temporal separation of high current (only during start-up) and low current (during normal operation) resolves the contradiction between ensuring reliable start-up and preventing crystal damage from sustained high drive levels.
2Measurement precision
If complex amplitude monitoring and feedback circuits are used to control bias current, then the drive level can be precisely controlled, but the device complexity and power consumption increase
Solution Approach 1:
The patent extracts and eliminates the complex amplitude monitoring and feedback control circuits from the oscillator design. Instead of using continuous feedback to control the bias current, the invention uses a simple time-based approach where the bias current is set to a high start-up value for a predetermined time period, then reduced to a lower operating value. This removes the need for expensive high-quality components and complex signal processing circuits while still achieving reliable oscillator start-up and operation.
3Measurement precision
If complex amplitude monitoring and feedback circuits are used to control bias current, then the drive level can be precisely controlled, but power consumption increases
Solution Approach 1:
The patent extracts and eliminates the power-consuming amplitude monitoring and feedback control circuits. The new approach uses a simple time-based control method where the bias current is set to a high start-up value for a predetermined time period, then reduced to a lower operating value. This eliminates the need for continuous rectifying, A/D-converting, and D/A-converting operations, significantly reducing power consumption while maintaining reliable oscillator operation.
4Object-affected harmful factors
If the drive level is reduced to prevent crystal damage, then the crystal operates safely, but the oscillator may fail to start up reliably
Solution Approach 1:
The patent applies preliminary action by establishing a high bias current level before the oscillator starts oscillating. This high start-up value ensures that the oscillator can reliably begin oscillating even with crystals that have varying properties. After a predetermined time delay that allows the oscillator to stabilize, the bias current is then reduced to a lower operating value that prevents crystal damage during normal operation. This temporal sequencing resolves the contradiction between ensuring reliable start-up and preventing crystal damage.
Data Source
AI summary
The method concerns the reliable start-up of a crystal oscillator where the drive levels the crystal is subjected to are kept low in order to avoid over-driving the crystal. After applying a start-up value of a parameter controlling the drive level where the drive level associated with the start-up value is rather high such that reliable start-up is ensured the parameter is modified step-wise so as to reduce the drive level until the crystal oscillator ceases to operate regularly. To assess whether this is the case, the frequency of the crystal oscillator is compared with the frequency of an auxiliary oscillator. A safety margin is added to the parameter and the result stored in a non-volatile memory as an operating value. The crystal oscillator is then restarted with the start-up value and after a delay the operating value is applied.