Oscillator Trigger Circuit With Adjustable Hysteresis and Duty Cycle
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Solution Overview
Problem
Traditional Schmidt triggers exhibit high power consumption, significant interference with other circuit modules due to peak current, and are sensitive to manufacturing processes, making it difficult to control duty cycles in crystal oscillators.
Innovation Solution
A trigger system comprising a bias transistor, comparator transistor, switch transistors, and a shunt transistor, which scales MOS transistors proportionally to adjust hysteresis and duty cycles, 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 to enhance the noise margin of the oscillator, then the noise margin is improved, but the power consumption increases greatly due to large peak current in the flipped intermediate state
Solution Approach 1:
The patent changes the operating parameters of the trigger by introducing a bias voltage input terminal and a bias transistor that scales with the oscillator transistors. This adjusts the threshold voltages and neutral point to match the oscillator's output characteristics, enabling the trigger to operate efficiently with the non-full swing sine wave output, thereby reducing peak current and power consumption while maintaining noise margin enhancement capability
Solution Approach 2:
The patent introduces adjustable hysteresis control through the bias transistor scaling ratio N, allowing the trigger's hysteresis interval to be dynamically adjusted to match the oscillator's amplitude characteristics. This dynamic adaptation prevents excessive peak current while maintaining the noise margin benefit
2Reliability
If a traditional Schmidt trigger with intense positive feedback is used, then the hysteresis interval is large, but the duty cycle control becomes difficult and the neutral point voltage changes obviously with manufacture process
Solution Approach 1:
The patent introduces a bias voltage input terminal and a bias transistor with scaling ratio N that allows the threshold voltages and neutral point to be adjusted according to the oscillator's output characteristics. This parameter adjustment compensates for manufacture process variations and enables precise duty cycle control while maintaining a stable hysteresis interval
Solution Approach 2:
The patent implements a feedback mechanism where the bias transistor scaling ratio N is designed to match the ratio between the oscillator's pull-up and pull-down transistor sizes. This feedback-like adjustment ensures that the trigger's neutral point and threshold voltages automatically adapt to process variations, maintaining stable duty cycle and hysteresis characteristics
3Reliability
If a traditional Schmidt trigger is applied to an oscillator with non-full swing sine wave output, then the noise margin is enhanced, but the power consumption increases due to mismatch between trigger threshold and oscillator output characteristics
Solution Approach 1:
The patent adjusts the trigger's threshold voltages and neutral point parameters by introducing a bias voltage input and a bias transistor with scaling ratio N. This parameter customization matches the trigger's characteristics to the oscillator's non-full swing sine wave output, enabling efficient operation with reduced peak current while maintaining noise margin enhancement
Solution Approach 2:
The patent makes the trigger adaptable to different oscillator output characteristics by allowing the bias voltage and scaling ratio N to be adjusted. This dynamic configuration enables the trigger to work optimally with non-full swing sine wave outputs, reducing power consumption while maintaining noise margin benefits
Data Source
AI summary
A trigger, includes: a first voltage input terminal; a bias voltage input terminal; a first bias transistor having a scaling of N to a first component of an external device; a comparator transistor having a scaling of N to a second component of the external device; a first switch transistor and a second switch transistor; a shunt transistor having a control terminal connected to the first voltage input terminal, a second terminal connected to the second terminal of the second switch transistor, and a first terminal connected to the first terminal of the comparator transistor. The shunt transistor has an enlarging scale of M to the comparator transistor. A 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.