Level Shifter Retention Across Voltage Domains During Power-Down
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Solution Overview
Problem
Existing system-on-chip (SoC) devices face challenges in retaining data at the interface between low and high voltage domains, particularly when the on-chip components are powered down, as the I/O controller must remain active to maintain signal states, leading to increased power consumption and potential signal noise.
Innovation Solution
A level shifter and control signal generator apparatus that switches between retention and transmission states based on a second voltage control signal, allowing data retention even when the first voltage domain is powered down, with the control signal generator maintaining the retention state if the controller becomes inactive, thus enabling complete power-down of the SoC without compromising data retention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the I/O controller remains active to maintain data retention at the interface, then data retention is achieved, but power consumption increases
Solution Approach 1:
The system is divided into two voltage domains (first voltage domain with lower voltage and second voltage domain with higher voltage), allowing independent power management of each domain. The level shifter acts as an interface between these segmented domains, enabling the first voltage domain to be powered down while maintaining data retention in the second voltage domain through the control signal generator.
Solution Approach 2:
The control signal generator is configured to maintain the second voltage control signal at the first value (retention state) if the controller becomes inactive. This preliminary action ensures that data retention is automatically preserved without requiring the controller to remain active, thereby reducing power consumption while maintaining reliability.
2Use of energy by moving object
If the I/O controller is powered down to reduce power consumption, then power consumption decreases, but data retention at the interface is compromised
Solution Approach 1:
The control signal generator acts as an intermediary between the controller and the level shifter. It receives control signals from the controller in the first voltage domain and generates corresponding control signals for the level shifter in the second voltage domain. This intermediary mechanism allows the controller to be powered down while the control signal generator maintains the retention state, ensuring data retention without continuous controller activity.
Solution Approach 2:
The control signal generator is designed to autonomously maintain the second voltage control signal at the retention value when the controller becomes inactive. This self-service capability allows the system to automatically preserve data retention state without requiring continuous intervention from the powered-down controller, enabling complete power-down of the SoC while maintaining interface data integrity.
3Reliability
If the level shifter continuously monitors control signals to maintain data retention, then data retention is ensured, but signal noise increases
Solution Approach 1:
Instead of continuous monitoring, the system uses periodic or event-driven updates of control signals. The control signal generator updates the second voltage control signal based on changes in the first voltage control signal or when the controller becomes inactive, rather than continuously monitoring. This periodic action reduces signal noise while maintaining data retention reliability.
Data Source
AI summary
An interface between first and second voltage domains is provided. A level shifter is configured to receive an input signal from the first voltage domain and to level shift the input signal to provide an output signal for passing to the second voltage domain. A control signal generator is configured to generate a second voltage domain control signal in dependence on at least one first voltage domain control signal from a controller in the first voltage domain. The level shifter is configured to be in a retention state when the second voltage domain control signal has a first value, such that its output signal is held constant even when the controller becomes not actively driven by the first voltage supply. The level shifter is configured to be in a transmission state when the second voltage domain control signal has a second value, wherein the output signal depends on the input signal.