IoT Circuit Power Biasing for Idle Leakage Reduction
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Solution Overview
Problem
IoT applications face challenges in minimizing leakage currents during idle periods to conserve energy without degrading operating performance, as reducing nominal VDD supply voltage compromises circuit performance.
Innovation Solution
The method involves reducing the first internal supply voltage (VDDa) by one threshold voltage (Vtp) and increasing the second internal supply voltage (VSSa) by one threshold voltage (Vtn) during idle states, while reverse biasing transistor body regions, and rapidly transitioning these voltages back during non-idle states to maintain performance and save energy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the nominal VDD supply voltage is reduced to minimize leakage currents during idle periods, then energy consumption is reduced, but circuit operating performance degrades due to lower operating frequency
Solution Approach 1:
The supply voltage is segmented into two distinct levels: a first supply voltage level during idle periods for minimal leakage current, and a second supply voltage level during active periods for optimal operating frequency. This segmentation allows the system to optimize for energy consumption during idle states while maintaining performance during active states.
Solution Approach 2:
The supply voltage is dynamically adjusted between two levels based on the operational state of the circuit. During idle periods, the voltage is reduced to minimize leakage; during active periods, the voltage is increased to maintain operating frequency. This dynamic adjustment resolves the contradiction by adapting the voltage level to the current operational requirements.
2Duration of action of stationary object
If the nominal VDD supply voltage is reduced to save energy during idle states, then battery life is extended, but the wake-up time increases due to slower voltage recovery
Solution Approach 1:
The circuit maintains certain pre-charged nodes and keeps critical circuit elements in a prepared state during idle periods, so that upon activation, the voltage recovery and circuit initialization can proceed rapidly. This preliminary preparation reduces the wake-up time penalty while still allowing energy savings during idle states.
Solution Approach 2:
Different parts of the circuit are treated differently during voltage transitions: critical path elements receive priority voltage restoration to minimize wake-up time, while non-critical elements can tolerate slower recovery. This localized quality approach ensures fast wake-up performance without requiring all circuit elements to recover simultaneously.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach reduces leakage currents and energy consumption during idle states without affecting operating performance during non-idle states, extending battery life and enabling rapid wake-up times.
Implementation Method 1
a first internal supply voltage (VDDa) used to supply the internal circuitry is reduced from the VDD supply voltage to a voltage lower than the VDD supply voltage during an idle state of the IoT application, thereby reducing leakage currents in the internal circuitry during the idle state. In one embodiment, the first internal supply voltage (VDDa) is reduced to a voltage that is one threshold voltage (Vtp) lower than the VDD supply voltage.
Implementation Method 2
body regions of transistors within the internal circuitry are reverse biased during the idle state to further reduce leakage currents within the internal circuitry. More specifically, p-type body regions of p-channel transistors of the internal circuitry can be biased with the VDD supply voltage, and the n-type body regions of n-channel transistors within the internal circuitry can be biased with the VSS supply voltage during the idle state.
Data Source
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Figure 2
AI summary
Energy consumption is reduced within an Internet of Things (IoT) device, without degrading operating performance of the corresponding internal circuitry. A first internal supply voltage (VDDa) used to supply the internal circuitry is reduced from a VDD supply voltage to a lower voltage during an idle state, thereby reducing leakage currents in the internal circuitry. The first internal supply voltage (VDDa) may be reduced to a voltage that is one threshold voltage (Vtp) lower than the VDD supply voltage. A second internal supply voltage (VSSa) used to supply the internal circuitry is increased from the VSS supply voltage to a voltage higher than the VSS supply voltage during the idle state, thereby further reducing leakage currents in the internal circuitry. The second internal supply voltage (VSSa) may be increased to a voltage that is one threshold voltage (Vtn) higher than the VSS supply voltage.