Power Gating Circuit Using Miller Feedback to Limit In-Rush Current
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Solution Overview
Problem
The existing power gating techniques in integrated circuits face challenges in limiting in-rush current during power-up, which can be detrimental to the functional circuit and neighboring circuits, and conventional methods like inverter chains increase leakage current, counteracting the power consumption reduction benefits.
Innovation Solution
The integration of power gating transistors with Miller capacitance between their drain and gate terminals, along with a resistive element and a switching device, creates a feedback mechanism that reduces the slew rate of the gate drive voltage, limiting the in-rush current without the need for an inverter chain, thereby reducing leakage current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If an inverter chain is used to delay the control signal and stagger the timing of power gating transistors, then the in-rush current is reduced, but the leakage current increases due to the inverters being always on
Solution Approach 1:
The patent extracts and eliminates the inverter chain from the circuit, replacing it with a direct control mechanism using a switching device and resistive element that does not require always-on intermediate gates, thereby removing the source of leakage current while maintaining in-rush current limiting functionality
Solution Approach 2:
The patent introduces a resistive element as an intermediary between the switching device and the gate terminal, creating an RC time constant that provides the necessary delay and staggering effect without requiring active inverter components, thus achieving in-rush current reduction without the penalty of continuous leakage
2Speed
If the in-rush current is allowed to flow freely during power up, then the power gating transistor switches on quickly, but the in-rush current may exceed physical limits and destroy the functional circuit or reduce voltage levels in neighboring circuits
Solution Approach 1:
The patent applies beforehand cushioning by using the resistive element and Miller capacitance to create a controlled ramping effect on the gate voltage, which gradually activates the power gating transistor rather than allowing instantaneous full-power switching, thus cushioning the in-rush current before it can reach harmful levels
Solution Approach 2:
The patent utilizes the Miller capacitance effect as a feedback mechanism where the capacitance between drain and gate terminals creates a voltage-dependent delay that automatically regulates the switching speed, reducing the slew rate of the gate drive voltage and limiting in-rush current without external control circuitry
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 effectively limits the in-rush current to below the saturation current of the power gating transistor, reducing the peak in-rush current and minimizing leakage current, thus enhancing power management efficiency while maintaining circuit functionality.
Implementation Method 1
said at least one power gating transistor is configured to provide a Miller capacitance between said drain terminal and said gate terminal
Implementation Method 2
a resistive element coupled between said switching device and said gate terminal
Data Source
AI summary
A functional circuit is coupled to a power supply conductor by at least one power gating transistor. A switching device applies a gate drive voltage to a gate terminal of the power gating transistor via a resistive element. The power gating transistor provides a Miller capacitance between its drain and gate terminals. The Miller capacitance, the resistance of the resistive element, and the drive strength of the switching device are configured such that, in response to the switching device switching the gate drive voltage to allow more current to pass through the power gating transistor, the Miller capacitance provides a feedback mechanism competing against the switching device to reduce the slew rate of the gate drive voltage such that the current passing between the power gate supply conductor and the functional circuit through the power gating transistor is less than the saturation current of the power gating transistor.