Ring Oscillator Supply Voltage Sensing for Low-Power ICs
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Solution Overview
Problem
Conventional supply voltage sensors for integrated circuits face challenges in achieving high impedance and linearity when operating on low power, particularly due to the limitations of digital logic processes which lack precision analog components.
Innovation Solution
A supply voltage sensor using a ring oscillator sensor coupled with a resistor and multiplier circuits to process the input voltage, allowing for non-linear impedance handling and post-processing to achieve accurate digitization and regulation of supply voltages ranging from a few volts to twenty-five volts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a resistive voltage divider is used to compress the voltage range, then the voltage sensing capability is improved, but the impedance requirement becomes very high which conflicts with low power operation
Solution Approach 1:
The patent changes the operating parameters of the voltage divider by using switched capacitors to simulate high resistance values. Instead of using actual high-value resistors that would consume power, the system uses capacitors switched at specific frequencies to create effective high impedance, thereby achieving both high sensing capability and low power consumption.
Solution Approach 2:
The patent replaces the traditional resistive voltage divider with a switched capacitor-based voltage divider. This substitution uses digital switching mechanisms to achieve the voltage division function, eliminating the need for physical high-value resistors and enabling low-power operation while maintaining measurement precision.
2Measurement precision
If precision analog components are used to achieve good linearity, then the measurement accuracy is improved, but the device complexity increases and such components are not available on digital logic processes
Solution Approach 1:
The patent uses digital copying and processing techniques to achieve linearity correction. Instead of relying on precision analog components, the system digitizes the voltage signal and applies digital correction algorithms to compensate for non-linearity, thereby achieving high measurement accuracy using only digital logic components available on standard digital processes.
Solution Approach 2:
The patent segments the voltage sensing function into multiple discrete digital steps. By using switched capacitors that can be individually controlled, the system creates a segmented approximation of the voltage signal that can be processed digitally, replacing complex analog circuitry with simpler digital switching and processing stages.
3Use of energy by moving object
If high impedance is used for the voltage divider to operate on low power, then the power consumption is reduced, but the impedance matching and signal integrity become difficult to achieve
Solution Approach 1:
The patent employs periodic switching of capacitors to create the voltage division function. By switching the capacitors at regular intervals synchronized with the system clock, the system achieves effective high impedance while maintaining signal integrity through periodic sampling and holding techniques that prevent signal degradation.
Solution Approach 2:
The patent introduces switched capacitors as intermediary elements between the voltage divider and the digital processing stages. These capacitors act as buffers that maintain signal integrity by providing low impedance paths during switching operations while presenting high impedance to the overall circuit, thereby decoupling the power consumption from signal integrity requirements.
Data Source
AI summary
A method and an apparatus to sense supply voltage have been disclosed. In one embodiment, the apparatus includes a resistor having a first end and a second end, the first end coupled to a voltage supply and a ring oscillator sensor coupled between the second end of the resistor and ground, the ring oscillator sensor having an output coupled to a computational element. Other embodiments have been claimed and described.