Oscillation Stop Detection and Restart in Semiconductor Clock Circuits
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Solution Overview
Problem
Existing semiconductor integrated circuits fail to reliably detect and restart a vibrator-type oscillation circuit when it stops due to power supply voltage fluctuations, limiting the effectiveness of the fail-safe function.
Innovation Solution
A semiconductor integrated circuit that includes a main oscillation circuit, a ring oscillator, a main clock detection circuit, and a switch circuit, which monitors the main clock signal and switches the combination of elements in the oscillation circuit to restart it, with the option to use a high-speed RC oscillator as a backup clock when necessary.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a watchdog timer monitors LSI malfunction using a ring oscillator clock, then malfunction monitoring is achieved independently of the vibrator-type oscillation circuit, but automatic operation recovery cannot be performed when the vibrator-type oscillation circuit stops
Solution Approach 1:
An oscillation stop detection circuit is introduced as an intermediary component that specifically monitors the vibrator-type oscillation circuit's operation state. This circuit detects oscillation stop conditions and triggers automatic recovery operations, separating the monitoring function from the general watchdog timer while enabling targeted automatic recovery for the oscillation circuit.
Solution Approach 2:
The system implements self-service through automatic recovery mechanisms where the oscillation stop detection circuit automatically controls power supply voltage to restart the oscillation circuit without external intervention. The watchdog timer and oscillation stop detection circuit work together to enable the system to self-diagnose and self-recover from oscillation stop conditions.
2Measurement precision
If the oscillation stop detection circuit processes output at potential level, then oscillation stop detection is achieved, but intended operation cannot be guaranteed during power supply voltage fluctuation
Solution Approach 1:
The oscillation stop detection circuit dynamically adjusts its detection threshold and operational parameters based on the actual power supply voltage level. During voltage fluctuation, the circuit adapts its reference levels to maintain accurate oscillation stop detection while ensuring the oscillation circuit can still restart when conditions improve, thus guaranteeing intended operation under varying voltage conditions.
3Measurement precision
If a high-accuracy vibrator-type oscillation circuit is used for main clock, then clock accuracy is improved, but the circuit is vulnerable to stop due to power supply voltage fluctuation
Solution Approach 1:
The system prepares for potential oscillation stop events by pre-configuring the oscillation stop detection circuit and automatic recovery mechanisms. When voltage fluctuation occurs, the detection circuit is already in place to immediately detect oscillation stop conditions, and the recovery circuitry is pre-positioned to automatically restore power supply voltage and restart the oscillation circuit, cushioning against the harmful effects of voltage fluctuation before they can cause system failure.
Data Source
AI summary
A semiconductor integrated circuit capable of reliably detecting oscillation stop of a vibrator-type oscillation circuit and reliably restarting the oscillation circuit when oscillation stop is detected is provided. The semiconductor integrated circuit includes one or more main oscillation circuits configured to generate a main clock signal by a vibrator, a ring oscillator configured to always operate independently of the main oscillation circuit, a main clock detection circuit configured to monitor the main clock signal on the basis of an output clock signal of the ring oscillator and to determine an operation state of the main oscillation circuit, and an switch circuit configured to switch a combination of elements making up the main oscillation circuit in response to a detection result of the main clock detection circuit.