Dual-Domain Isolated Level Shifter for Power-Gating Stability
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Solution Overview
Problem
Integrated circuits with multiple power domains face challenges in voltage level shifting, leading to indeterminate voltage levels during power gating, which result in crowbar current and unwanted signal transitions due to the lack of extra circuitry to compensate for these levels.
Innovation Solution
The implementation of level shifters that utilize isolate enable signals based on different power supply voltages to manage voltage levels, preventing glitches and maintaining stable output states by isolating circuit paths and clamping nodes to specific values during power gating transitions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If voltage level shifting is performed between power domains during power gating, then signal compatibility is achieved, but indeterminate voltage levels occur causing crowbar current and unwanted signal transitions
Solution Approach 1:
The isolation enable signal is generated before the power gating transition occurs, preparing the level shifter for the upcoming voltage change. This preliminary action ensures that the level shifter is properly isolated and clamped before indeterminate voltage levels can develop, preventing crowbar current from flowing.
Solution Approach 2:
The level shifter acts as an intermediary circuit between the first and second power domains. It includes isolation circuitry that mediates the voltage transition by clamping internal nodes to stable voltage levels during power gating, preventing direct coupling that would cause crowbar current.
2Object-generated harmful factors
If isolation circuitry is added to prevent crowbar current, then harmful effects are reduced, but device complexity increases
Solution Approach 1:
The isolation functionality is merged with the level shifting operation. The same circuitry that performs voltage level translation also handles the isolation and clamping functions during power gating, eliminating the need for separate isolation components and reducing overall circuit complexity.
Solution Approach 2:
The level shifter circuit is designed to perform multiple functions: voltage level translation between power domains, isolation during power gating transitions, and clamping of internal nodes. This multi-functionality reduces the need for additional dedicated isolation circuitry.
3Device complexity
If level shifter operates during power gating without isolation, then device simplicity is maintained, but spurious voltage levels and glitches occur
Solution Approach 1:
The isolation enable signal is generated in advance of the power gating event, allowing the level shifter to prepare its internal state before the voltage transition. This preliminary isolation action stabilizes internal nodes and prevents spurious voltage levels from appearing at the output during the transition.
Data Source
AI summary
A system and method for efficiently handling voltage level shifting are contemplated. In various embodiments, a first level shifter receives a first isolate enable signal based on a first power supply voltage and a second isolate enable signal based on a second power supply voltage different from the first power supply voltage. A second level shifter generates the first isolate enable signal based on both the second isolate enable signal and the first power supply voltage. A circuit block generates a data signal based on the first power supply voltage. When it is determined that isolation for the first level shifter is enabled, the first level shifter generates a voltage level on an internal particular node to a particular voltage level based on the first isolate enable signal, and also prevents, using the second isolate enable signal, the data signal from setting a voltage level on the particular node.