Oscillator IC Mode Switching to Prevent High-Voltage Transistor Stress
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Solution Overview
Problem
Integrated circuits for Temperature Compensated X'tal Oscillators (TCXOs) face challenges in maintaining high-accuracy temperature compensation and reliability due to unequal temperature changes between the crystal vibrator and the temperature sensor, and the application of high voltage for mode switching causes stress on transistors, leading to characteristic degradation and increased costs.
Innovation Solution
An integrated circuit design that includes a mode switching circuit allowing voltage-based mode switching, a control circuit to stop the oscillation circuit in the second mode, and a configuration that reduces stress on transistors by defaulting to a power-down mode during high voltage applications, thereby maintaining reliability and reducing costs through microfabrication processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If high voltage is applied to the power supply terminal for mode switching, then mode switching is achieved, but stress on transistors increases causing characteristic degradation
Solution Approach 1:
The oscillation circuit is stopped before applying high voltage for mode switching. The control circuit detects the mode switching signal and activates the oscillation stop signal beforehand, ensuring the transistor is not subjected to high voltage stress during operation, thus preventing characteristic degradation while enabling mode switching
Solution Approach 2:
The invention provides protective control by stopping the oscillation circuit in advance before mode switching occurs. This preliminary protective action cushions the transistor against the harmful effects of high voltage application, preventing HCI, NBTI, and TDDB degradation mechanisms
2Reliability
If the oscillation circuit is stopped in the second mode, then stress on transistors is reduced, but the ability to process serial signals is compromised
Solution Approach 1:
The invention dynamically controls the oscillation circuit based on the operational mode. In the first mode, the oscillation circuit operates normally to provide timing signals. In the second mode, it is stopped to prevent transistor degradation during high voltage application. The control circuit dynamically adjusts the oscillation state according to the detected mode, optimizing both reliability and functionality
3Area of stationary object
If microfabrication process is used to reduce IC area and cost, then area and cost are reduced, but transistor stress from high voltage mode switching increases
Solution Approach 1:
The oscillation circuit is stopped before high voltage is applied for mode switching in microfabricated ICs. This preliminary action prevents transistor stress and characteristic degradation, enabling the safe use of cost-effective microfabrication processes while maintaining device reliability
Solution Approach 2:
The invention converts the potentially harmful high voltage mode switching into a beneficial process by controlling the timing. By stopping the oscillation circuit before high voltage application, the harmful stress on transistors is eliminated, allowing microfabrication processes to be used without compromising reliability, thus achieving cost reduction
Data Source
AI summary
An oscillator IC includes a VDD terminal (first terminal), an OUT terminal (second terminal), an oscillation circuit for oscillating a resonator element, a mode switching circuit that switches between a normal mode (the first mode in which an oscillation signal output by the oscillation circuit is output from the OUT terminal) and a serial I/F mode (the second mode in which a signal than the oscillation signal is output or input from the OUT terminal) based on a voltage of the VDD terminal, and a control circuit that controls stop of the oscillation circuit in the serial I/F mode based on setting information that can be changed from outside.