Power OK Distribution for Multi-Voltage ICs
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Solution Overview
Problem
Powering up integrated circuits (ICs) with multiple power supplies requires a specific sequence to prevent damage and ensure proper functioning, as applying power in the wrong sequence can lead to circuit damage or failure to initialize correctly.
Innovation Solution
A method and apparatus where each power domain includes a power-sensing unit that detects the presence of power and receives a power ok signal from an upstream domain, asserting a downstream power ok signal only when both conditions are met, utilizing a daisy-chain topology and level shifting circuitry to ensure accurate power sequencing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If power is applied to multiple power supplies simultaneously, then the IC can be powered up quickly, but circuit damage or destruction may occur due to improper power sequencing
Solution Approach 1:
The patent implements power-sensing units in each power domain that detect the presence of power before allowing downstream domains to be powered up. This preliminary detection and sequencing action prevents circuit damage by ensuring proper power-up order, while still enabling relatively quick initialization through automated sensing and signal propagation throughout the IC.
2Reliability
If power sequencing control is implemented to prevent damage, then circuit safety is improved, but the power-up process becomes more complex
Solution Approach 1:
The patent divides the IC into multiple power domains, each with its own power-sensing unit. This segmentation allows independent control and monitoring of each domain's power state, simplifying the overall sequencing logic while maintaining circuit safety. Each domain can be managed independently through daisy-chained power-ok signals, reducing the complexity of centralized power management.
Solution Approach 2:
Each power domain contains a power-sensing unit that automatically detects the presence of power and generates appropriate power-ok signals without external intervention. This self-service mechanism eliminates the need for complex external power sequencing control circuits, as each domain autonomously determines when it is safe to be powered up and signals downstream domains accordingly.
3Reliability
If power-ok signals are propagated through daisy-chain topology, then proper power sequencing is ensured, but signal transmission delays increase
Solution Approach 1:
The power-sensing units perform preliminary detection of power presence in each domain before propagating power-ok signals downstream. This preliminary action ensures that each domain is fully powered and stable before downstream domains are activated, maintaining sequencing accuracy. The daisy-chain topology efficiently propagates these signals with minimal delay compared to alternative sequencing mechanisms.
Data Source
AI summary
A method and apparatus for powering up an integrated circuit (IC). An IC includes a plurality of power domains each coupled to receive power from one of a plurality of power sources. Each power domain includes a power-sensing unit. A power-sensing unit in a first one of the plurality of power domains is coupled to receive a first power ok signal from an upstream power domain, and is configured to assert a second power ok signal to be provided to a second power domain. A power-sensing unit in the second power domain is coupled to detect the presence of voltage in the first power domain, and to receive the first power ok signal. When the power-sensing unit in the second power domain has both sensed the presence of power in the first power domain and received the second power ok signal, a third power ok signal is asserted.