Power Domain Isolation Using Passgate Control Circuits
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Solution Overview
Problem
In modern integrated circuits, power domains with different voltage requirements or power saving needs often face communication inhibition when one or both are powered down, leading to indeterminate data and power contention issues between interfaced units.
Innovation Solution
The implementation of passgate circuits and a control circuit to isolate circuitry between power domains during power down and up operations, ensuring that circuitry in one domain is powered down or up only after the other, and that passgate circuits are deactivated before powering down or after powering up to prevent erroneous data transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If passgate circuits are used to interface circuitry between power domains, then communication between functional units is enabled, but indeterminate data and power contention issues occur during power down operations
Solution Approach 1:
The control circuit deactivates the passgate circuits before powering down the circuitry in the second power domain. This preliminary action ensures that the isolation is established prior to the power transition, preventing indeterminate data from being conveyed to the first power domain and avoiding power contention issues.
2Loss of energy
If circuitry in different power domains is powered down independently for power saving, then power consumption is reduced, but communication inhibition and erroneous data transmission occur
Solution Approach 1:
The control circuit acts as an intermediary that coordinates the power down operations between different power domains. It manages the sequencing of passgate deactivation and power domain shutdown, ensuring that isolation is properly established before power transitions occur, thus maintaining communication reliability while enabling power saving operations.
3Ease of operation
If passgate circuits remain active during power down, then signal transmission is maintained, but power contention and indeterminate data are conveyed between power domains
Solution Approach 1:
The harmful effect is extracted by removing the passgate circuits from the active state before the power down operation begins. The control circuit specifically targets and deactivates the passgate circuits, separating them from the power domain being shut down. This extraction prevents the harmful effects of power contention and indeterminate data transmission while allowing the power saving operation to proceed.
Data Source
AI summary
An apparatus and method for isolating circuitry from one power domain from that of another power domain prior to performing a power down operation is disclosed. In one embodiment, circuitry in a first power domain is coupled to receive signals based on outputs from circuitry in a second power domain. The signals may be conveyed to the circuitry in the first power domain via passgate circuits. When powering down the circuitry of the first and second power domains, a control circuit may first deactivate the passgate circuits in order to isolate the circuitry of the first power domain from that of the second power domain. The circuitry in the second power domain may be powered off subsequent to deactivating the passgate circuits. The circuitry in the first power domain may be powered off subsequent to powering off the circuitry in the second power domain.