Low Voltage Regulator Virtual Ground Back-Biasing
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Solution Overview
Problem
Existing voltage regulators cannot combine source back-biasing with low voltage regulation to maintain adequate noise margin in source-biased power domains, as the output voltage of low voltage regulators is insufficient to support logic circuits during back-biasing, leading to reduced reliability and increased leakage current.
Innovation Solution
A low voltage regulator is coupled to a source-biased power domain with its common connected to the virtual ground, allowing the output voltage to rise with the virtual ground voltage, maintaining the same effective voltage across transistors during back-biasing, thereby reducing leakage current while maintaining noise margin.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a low voltage regulator is used to reduce bias current in source-biased power domains, then power consumption is reduced, but noise margin becomes insufficient
Solution Approach 1:
The patent changes the reference voltage parameter of the low voltage regulator from true ground to virtual ground. By coupling the regulator's reference input to the virtual ground (which is raised during back-biasing), the regulator's output voltage automatically tracks and maintains the correct voltage differential, preserving noise margin while keeping the regulator operating at low current.
2Loss of energy
If virtual ground is raised for back-biasing to reduce leakage current, then leakage current is reduced, but the effective voltage across circuits decreases
Solution Approach 1:
The patent introduces the virtual ground as an intermediary reference voltage between true ground and the regulator output. The virtual ground serves as a floating reference that moves with the back-bias voltage, allowing the regulator to maintain proper voltage levels across circuits while the virtual ground itself provides the leakage reduction benefit of back-biasing.
3Reliability
If main voltage regulator is used to maintain noise margin in source-biased power domains, then noise margin is adequate, but power consumption increases
Solution Approach 1:
The patent changes the operating parameters of the voltage regulator by reconfiguring its reference voltage from true ground to virtual ground. This parameter change allows the same low voltage regulator to operate effectively in source-biased power domains, maintaining noise margin while consuming minimal power, replacing the need for the power-hungry main voltage regulator.
Data Source
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AI summary
A common (ground) of a low voltage regulator is connected to a virtual common (ground) of an integrated circuit device that is also connected to transistor sources but isolated from a true ground connected to the substrate of the integrated circuit device. The regulated output voltage from the low voltage regulator rises the same as the virtual ground voltage rises when back-biased sufficient to reduce leakage current to an acceptable level in a given process technology. Therefore, the output of the low voltage regulator will maintain a normal operating voltage for the logic during a power saving back-biased condition.