Voltage Sensor In-Range Check Using Ring Oscillator Heartbeat
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Solution Overview
Problem
Existing voltage sensors fail to reliably detect voltage deviations in safety-critical applications, particularly in automotive electronics monitoring applications, due to their dependence on the DC voltage supply they monitor.
Innovation Solution
A system including a multi-phase ring oscillator (RO) configured to operate in a first voltage domain, a frequency counter configured to accumulate a plurality of phase cycles from the multi-phase RO, a frequency divider configured to generate a digital count word, and a heartbeat detector configured to detect a periodic recurrence of a heartbeat pulse to determine the integrity of the alarm state signal and the overall sensor operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a voltage sensor depends on the DC voltage supply it monitors, then the device complexity is reduced, but the reliability deteriorates because the sensor cannot reliably detect voltage deviations when its operation depends on the monitored supply
Solution Approach 1:
The voltage sensor is divided into two separate voltage domains: a first voltage domain for the ring oscillator and frequency counter, and a second voltage domain for the alarm processor and heartbeat detector. This segmentation allows the monitoring circuitry to operate independently from the monitored voltage supply, enabling reliable detection of voltage deviations without the sensor becoming dependent on the supply it monitors.
Solution Approach 2:
A heartbeat signal is introduced as an intermediary indicator to verify the proper functioning of the alarm circuitry. The heartbeat signal provides a reference that confirms the alarm processor and frequency counter are operating correctly, allowing the system to distinguish between actual voltage anomalies and sensor malfunctions.
2Reliability
If the voltage sensor operates in the same voltage domain as the monitored supply, then the ease of operation is improved, but the reliability deteriorates due to inability to detect overvoltage and undervoltage conditions accurately
Solution Approach 1:
The system separates the sensor operation into two distinct voltage domains. The first voltage domain contains the ring oscillator and frequency counter that monitor the DC voltage supply, while the second voltage domain contains the alarm processor and heartbeat detector that operate independently. This segmentation enables accurate detection of overvoltage and undervoltage conditions while maintaining operational simplicity through automated monitoring and alerting.
3Reliability
If a heartbeat detection mechanism is added to verify alarm state signal integrity, then the reliability is improved, but the device complexity increases
Solution Approach 1:
The heartbeat detection functionality is merged into the existing alarm processor circuitry. The alarm processor simultaneously handles both the alarm state signal processing and the heartbeat signal verification, eliminating the need for a completely separate verification system. This integration improves reliability through comprehensive monitoring while minimizing the increase in device complexity by utilizing shared computational resources.
Data Source
AI summary
Aspects of the disclosure are directed to voltage sensing for safety-critical applications. In accordance with one aspect, the disclosure includes generating an alarm state signal from a digital count word and a comparator state signal; generating a heartbeat signal by dividing down one of a plurality of multi-phase ring oscillator (RO) output waveforms; and generating an error interrupt signal and a warning interrupt signal in a voltage domain based on the alarm state signal and the heartbeat signal.