Ring Oscillator Substrate Bias for Power Reduction
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Solution Overview
Problem
High power supply voltage in semiconductor devices leads to increased current and power consumption due to excessive output current in non-volatile memory operations, such as in EEPROMs, where a high voltage is required for erasing and writing, resulting in inefficiencies.
Innovation Solution
A ring oscillator circuit design where the PMOS transistor in each inverter circuit has its substrate connected to the power supply voltage VDD, with the source connected to a second power supply voltage VREG, which acts as a constant voltage when VDD is higher than a predetermined value, causing a substrate bias effect that increases the threshold voltage and reduces oscillation frequency, thereby reducing current and power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the power supply voltage VDD is increased to enable high voltage generation for memory operations, then the output current IOUT increases proportionally, but current consumption and power consumption are excessively increased
Solution Approach 1:
The patent changes the threshold voltage parameter of the PMOS transistor by applying substrate bias. When VDD exceeds a predetermined voltage, the substrate bias effect automatically increases the threshold voltage, which reduces the oscillation frequency and consequently reduces the output current of the charge pump circuit, thereby reducing power consumption while maintaining sufficient high voltage generation capability
Solution Approach 2:
The patent implements a feedback mechanism where the substrate bias effect creates a natural feedback loop. As VDD increases, the threshold voltage automatically increases through substrate bias, which reduces oscillation frequency and output current, providing negative feedback that prevents excessive power consumption without requiring external control circuits
2Power
If the oscillation frequency is reduced to suppress output current and reduce power consumption, then current consumption decreases, but the ability to generate high voltage efficiently is compromised
Solution Approach 1:
The patent dynamically changes the threshold voltage parameter based on the power supply voltage level. By utilizing substrate bias, the threshold voltage increases only when VDD exceeds the predetermined voltage, thereby reducing oscillation frequency and output current specifically in high voltage regions while maintaining normal operation in standard voltage regions, preserving high voltage generation efficiency
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
The proposed solution effectively reduces current and power consumption by prolonging the charge and discharge time of inverter circuits and lowering oscillation frequency, especially in high power supply voltage regions, while maintaining efficient high voltage generation for memory operations.
Implementation Method 1
a potential difference is generated between the source and the substrate of the PMOS transistor in each of the inverter circuits. Due to a substrate bias effect, a threshold voltage rises
Data Source
AI summary
Provided are an oscillation circuit, a booster circuit, and a semiconductor device capable of reducing power consumption when a power supply voltage is high. In a ring oscillator circuit which is the oscillation circuit, a PMOS transistor in each of inverter circuits has a substrate connected to a first power supply voltage, and a source connected to a drain of a PMOS transistor, which is a first constant current element configured to control a supply current to the inverter circuit, and the PMOS transistor, which is the first constant current element, has a source connected to a second power supply voltage VREG, which serves as a constant voltage when the first power supply voltage is at a predetermined voltage or higher.