Integrated On-Chip Power-On Reset Circuit for Functional Safety
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Solution Overview
Problem
Implementing voltage detectors and supervisory functions outside a System On a Chip (SoC) increases system cost and fails to meet high-level functional safety standards specified by ISO 2626 and IEC 61508.
Innovation Solution
A fully integrated Power On Reset (POR) generation circuit with continuous voltage monitoring and redundant three-stage voltage detection, using an internal RC oscillator, crystal oscillator, and efuse module for trim value adjustment, ensuring reliable reset sequencing and diagnostic capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If voltage detectors and supervisory functions are implemented outside the SoC, then system cost increases, but functional safety requirements can be met
Solution Approach 1:
The patent integrates voltage detection circuits, supervisory functions, and reset generation directly into the SoC device. The voltage detection circuit includes multiple detection units with different threshold voltages that are embedded within the SoC architecture, eliminating the need for separate external supervisory components while maintaining functional safety compliance.
Solution Approach 2:
The integrated voltage detection circuit performs multiple functions: it monitors voltage levels across different rails, generates reset signals when thresholds are violated, provides supervisory oversight, and ensures functional safety compliance. This multi-functional integration reduces system complexity while meeting safety requirements.
2Reliability
If simple voltage detection is used, then device complexity is reduced, but reliability of reset functionality decreases
Solution Approach 1:
The voltage detection circuit is segmented into multiple independent detection units, each monitoring specific voltage rails with dedicated threshold voltages. This segmentation provides redundancy - if one detection unit fails, others continue to monitor and generate reset signals, thereby improving overall reliability while keeping each individual detection unit relatively simple.
Solution Approach 2:
The patent implements redundant detection units and supervisory functions that provide a safety buffer before complete system failure can occur. The multiple threshold voltages and overlapping monitoring coverage ensure that reset functionality is maintained even if individual components fail, cushioning against reliability risks.
Data Source
AI summary
A functional safety POR system requires implementing voltage detectors and supervisory functions in a complex SOC. These features are implemented within the SOC without external components. Three stages of voltage monitoring are implemented to ensure redundancy.