Crystal Oscillator Trigger Circuit With Adjustable Hysteresis
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Solution Overview
Problem
Traditional Schmidt triggers in oscillation systems exhibit high power consumption, significant interference, large hysteresis intervals, and sensitivity to manufacturing processes, leading to unstable duty cycles and increased noise margin requirements.
Innovation Solution
The oscillation system incorporates a crystal oscillator with a trigger configuration that includes bias and comparator transistors scaling MOS transistors proportionally, along with switch and shunt transistors to adjust hysteresis and duty cycle, reducing power consumption and interference while maintaining a high noise margin and insensitivity to manufacturing variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a traditional Schmidt trigger is used at the oscillator output terminal, then the noise margin of the oscillator is enhanced, but the power consumption becomes great
Solution Approach 1:
The patent changes the operating parameters of the trigger circuit by using a differential structure with balanced transistors, setting the threshold voltages to be symmetric around zero. This parameter change allows the trigger to achieve high noise margin while reducing power consumption by eliminating the large peak currents characteristic of traditional Schmidt triggers
2Reliability
If a traditional Schmidt trigger is used, then the noise margin is improved, but the output of the LDO hops causing interference to other circuit modules
Solution Approach 1:
The patent converts the potentially harmful peak currents into beneficial controlled current transitions by using the differential structure and hysteresis mechanism. The current transitions are shaped to be smooth and controlled, transforming the harmful LDO hopping into a stable operating condition that maintains noise margin without causing interference
3Reliability
If a traditional Schmidt trigger with intense positive feedback is used, then the hysteresis interval becomes large, but the duty cycle control becomes difficult
Solution Approach 1:
The patent introduces dynamic control elements that allow the hysteresis interval and threshold voltages to be adjusted in real-time. The differential structure with controllable bias currents enables dynamic adjustment of the switching thresholds, making the duty cycle controllable while maintaining adequate hysteresis for noise immunity
4Ease of manufacture
If traditional Schmidt trigger threshold voltages are used, then the flipping neutral point is at half power voltage, but the duty cycle becomes insensitive to manufacturing process variations
Solution Approach 1:
The patent changes the threshold voltage parameters from fixed half-power-voltage values to symmetric values around zero that are less sensitive to manufacturing variations. The differential structure provides inherent symmetry that compensates for process variations, while the bias control circuit allows adjustment of the neutral point to achieve the desired duty cycle
Data Source
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AI summary
An embodiment of the present invention provides a trigger and an oscillation system. The trigger includes: a first voltage input terminal; a bias voltage input terminal; a first bias transistor, configured to have a scaling of N to a first component of an external device connected to the trigger; a comparator transistor, configured to have a scaling of N to a second component of the external device connected to the trigger; a first switch transistor and a second switch transistor; a shunt transistor, wherein a control terminal of the shunt transistor is connected to the first voltage input terminal, a second terminal of the shunt transistor is connected to the second terminal of the second switch transistor, a first terminal of the shunt transistor is connected to the first terminal of the comparator transistor, and the shunt transistor is configured to have an enlarging scale of M to the comparator transistor; a voltage output terminal, wherein the voltage output terminal is respectively connected to the second terminal of the first switch transistor, the control terminal of the second switch transistor and the second terminal of the comparator transistor. The trigger according to the present invention has the advantages of low power consumption, less interference, adjustable hysteresis feature, rectifiable duty cycle and insensitivity to the process.