Temperature-Compensated Oscillation Circuit With Noise-Isolating Switch
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Solution Overview
Problem
Conventional oscillation circuits suffer from noise interference and increased area requirements due to parasitic capacitance in switching switches, which affects the frequency temperature characteristic and phase noise of temperature compensation circuits.
Innovation Solution
An oscillation circuit with a switching switch circuit comprising an oscillation output switch and a temperature sensor output switch, where transfer gate switches are connected in a two-stage serial manner with a third switch to a fixed potential, allowing selective output of oscillation or temperature sensor outputs, reducing noise leakage and area occupancy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a conventional switching switch is used to select between oscillation circuit and temperature compensation circuit, then the circuit can be operated in different modes, but parasitic capacitance causes noise leakage from the oscillation circuit to the temperature compensation circuit
Solution Approach 1:
A third switch connected to a fixed potential (ground) is introduced as an intermediary element between the transfer gate switches and the temperature compensation circuit. This third switch acts as a mediator that provides a safe discharge path for parasitic capacitance, preventing noise leakage to the temperature compensation circuit while maintaining the ability to switch between operational modes.
Solution Approach 2:
The harmful parasitic capacitance effect is extracted and redirected to a fixed potential through the third switch. By providing a dedicated path to ground, the parasitic capacitance is effectively removed from the signal path to the temperature compensation circuit, isolating the harmful effect from the sensitive circuit.
2Ease of operation
If conventional switching switches with separate input and output pads are used for each circuit, then each circuit can be independently controlled, but the input and output pads occupy large area in the apparatus
Solution Approach 1:
The output pad of the oscillation circuit and the input pad of the temperature compensation circuit are merged into a single shared pad. The switching functionality is achieved not through separate pads but through the transfer gate switches that can connect this shared pad to either circuit, thereby reducing the total pad area while maintaining independent control capability.
Solution Approach 2:
The shared pad serves multiple functions: it acts as the output pad for the oscillation circuit when the oscillation output switch is ON, and as the input pad for the temperature compensation circuit when the temperature sensor output switch is ON. This multi-functional design eliminates the need for separate dedicated pads for each circuit.
Data Source
AI summary
An oscillation section for which an output frequency is controlled based on a control signal depending on an ambient temperature; a temperature compensation circuit for supplying the control signal to this oscillation section; and a switching switch circuit consisting of an output buffer and a temperature sensor output switch for which ON and OFF are controlled so that any one of an oscillation output from the oscillation section and a temperature sensor output from the temperature compensation circuit is outputted. The temperature sensor output switch is structured so that transfer gate switches are connected in a two-stage serial manner and a third switch connected to a fixed potential is sandwiched between these connection points. When an oscillation output is outputted, the transfer gate switches are OFF and the third switch is ON and, when a temperature sensor output is outputted, the transfer gate switches are ON and the third switch is OFF.