Switched Capacitor Voltage Reference Circuit for Low Power CMOS
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Solution Overview
Problem
Existing voltage reference circuits require supply voltages greater than 1.25V and are not suitable for providing low voltage reference levels below 1V, while also consuming high power, making them unsuitable for low power applications and CMOS technologies.
Innovation Solution
A switched capacitor voltage reference circuit using three capacitors, a current source, multiple diode devices, and switching circuits, which allows for adjustable gain and wide voltage range operation, including low voltages, with a single current source and simple amplifier, eliminating the need for device trimming and achieving low power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional voltage reference circuits are used, then voltage reference stability is achieved, but supply voltage must be greater than 1.25V and power consumption is high
Solution Approach 1:
The patent changes the operating parameters of the voltage reference circuit by using a switched capacitor architecture that operates at low supply voltages (below 1.25V) and consumes minimal power. The circuit uses capacitive switching instead of continuous current flow, dramatically reducing power consumption while maintaining reference stability through periodic sampling and holding techniques.
Solution Approach 2:
The voltage reference circuit employs periodic switching operations where capacitors are charged and discharged in alternating phases. This periodic action allows the circuit to maintain accurate voltage references without continuous power consumption, as the switching occurs only during necessary update cycles rather than continuously.
2Measurement precision
If conventional voltage reference circuits are used, then voltage reference accuracy is achieved, but they cannot provide low voltage reference levels below 1V
Solution Approach 1:
The patent implements a dynamic switched capacitor architecture that can adapt its operating voltage range dynamically. The circuit uses controllable switches and capacitors that can be configured to operate accurately at various voltage levels including below 1V, providing versatility while maintaining precision through digital control mechanisms.
Solution Approach 2:
The voltage reference circuit is designed with universal functionality to provide accurate references across a wide voltage range including low voltages below 1V. The switched capacitor architecture with configurable switches and capacitors serves multiple voltage reference needs simultaneously, making the circuit adaptable to different application requirements.
3Temperature
If conventional voltage reference circuits are used, then temperature compensation is achieved, but device trimming and matching are required increasing complexity
Solution Approach 1:
The voltage reference circuit achieves temperature compensation through self-service mechanisms where the switched capacitor architecture inherently compensates for temperature drifts. The periodic switching and capacitive coupling automatically adjust for thermal effects without requiring external trimming or precise device matching, reducing complexity while maintaining temperature stability.
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 solution provides an inherently accurate and adjustable voltage reference with a wide voltage range, including low voltages, while reducing power consumption and eliminating the need for device matching, making it suitable for low power applications and CMOS technologies.
Implementation Method 1
A first capacitor is coupled between a first node and a second node. A second capacitor is coupled between the second node and an anode node. A third capacitor is coupled between the second node and a third node.
Implementation Method 2
The diode devices include at least one first diode device, each having an anode coupled to the anode node and each having a cathode coupled to a common node. The diode devices further include at least one second diode device, each having an anode coupled to the anode node and each having a cathode coupled to a fourth node.
Implementation Method 3
The amplifier has a first terminal coupled to the common node, a second terminal coupled to the second node, and an output terminal coupled to the output reference node.
Data Source
AI summary
A switched capacitor voltage reference including a single bias current source, three capacitors, diode devices, an amplifier and switching circuits for developing a temperature independent reference voltage. A single current source avoids having to match multiple current sources. A first capacitor and at least one diode device set a voltage having a negative temperature coefficient. A second capacitor and each of the diode devices set a voltage having a positive temperature coefficient. A third capacitor allows adjustable gain to enable a wide voltage range including a low voltage such as less than one volt. The switching circuits switch between multiple modes for developing and then combining the different temperature coefficient voltages. The topology allows a simple amplifier to be used. The topology is inherently accurate and does not require device trimming. An averaging method may be used to compensate for any mismatch between the diode devices.