Body Bias Control Circuit for Leakage Current Management
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Solution Overview
Problem
Transistors in integrated circuits face challenges in managing leakage current changes during body bias transitions, which can cause voltage regulation issues and operational problems due to rapid power draw changes, necessitating a controlled rate of change in leakage current to maintain tolerance and reduce startup or mode switching times.
Innovation Solution
A body bias control circuit that varies the effective rate of change of the body bias over time during transitions, with smaller changes occurring closer to the source voltage and larger changes further away, implemented using a quadratic manner to ensure the power supply voltage remains within tolerance while reducing transition times.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the body bias voltage is changed rapidly to reduce transition time, then the switching speed is improved, but the leakage current changes too quickly causing voltage regulation issues
Solution Approach 1:
The patent applies dynamics by making the rate of change of body bias voltage time-dependent. The circuit transitions from a static biasing approach to a dynamic one where the bias voltage changes at different rates during different phases of the transition, optimizing both speed and voltage regulation stability.
Solution Approach 2:
The patent changes the parameter of body bias voltage over time in a controlled manner. By adjusting the rate of change of the bias voltage parameter, the circuit achieves faster switching while maintaining voltage regulation within tolerance bands, resolving the contradiction between speed and reliability.
2Productivity
If the body bias voltage is changed quickly to reduce startup time, then the productivity is improved, but the leakage current change exceeds voltage tolerance
Solution Approach 1:
The patent employs periodic or staged action by dividing the bias voltage transition into multiple phases with different rates of change. This staged approach allows the system to achieve fast overall transition while ensuring that at no point does the leakage current change exceed voltage tolerance specifications.
Solution Approach 2:
The patent implements time-dependent parameter changes in the body bias voltage, transitioning from a single-rate change to a multi-rate approach. This enables the circuit to meet both the reduced startup time requirement and the voltage tolerance constraint by adjusting the bias voltage rate dynamically throughout the transition period.
3Loss of energy
If reverse body biasing is applied to raise threshold voltage and reduce leakage current, then power consumption is reduced, but switching speed decreases
Solution Approach 1:
The patent applies dynamics by implementing time-varying body bias voltage that can switch between forward and reverse biasing conditions. This dynamic control allows the circuit to optimize the trade-off between leakage current reduction and switching speed maintenance, applying reverse biasing only when needed for power savings while maintaining faster biasing conditions for speed-critical operations.
Solution Approach 2:
The patent changes the body bias voltage parameter dynamically to adjust the threshold voltage of the transistor. By controlling the rate and magnitude of bias voltage changes, the system can reduce leakage current through reverse biasing while minimizing the impact on switching speed, thus resolving the contradiction between energy loss and speed.
Data Source
AI summary
A body bias control circuit including an output coupled to provide a bias voltage to a body terminal. The body bias control circuit is configured to change the bias voltage from a first bias voltage to a second bias voltage over a period of time in which a magnitude of an effective rate of change of the bias voltage varies over the period of time. For voltages between the first and second bias voltages closer to a source voltage, the magnitude of the effective rate of change is smaller than for bias voltages between the first and second bias voltages further from the source voltage.