Switched-Capacitor Reference Circuit for Precise Temperature Sensing

The patent changes the fundamental parameter of the reference element from resistive to capacitive. By using a switched capacitor circuit to simulate the reference resistor function, the system exploits the fact that capacitor values are more stable over time and less susceptible to temperature drift and aging effects compared to resistors. The switched capacitor circuit uses precise clock signals and high-quality capacitors to achieve a virtual resistance that is far more stable than physical resistors.

The patent replaces the physical resistor component with an electronic circuit implementation using capacitors and switches. This substitution eliminates the need for a physical reference resistor and its associated mechanical/package strain issues. The switched capacitor circuit uses electronic switching elements controlled by clock signals to create a virtual resistance that is determined by capacitance values and switching frequency, rather than physical resistor properties.

The switched capacitor circuit performs multiple functions: it provides the reference resistance value, establishes the time constant for the RC circuit, and can be adjusted dynamically through clock frequency changes. The same capacitor and switch network that creates the virtual resistance also serves as part of the timing and control mechanism for the temperature sensing operation, reducing the need for separate components.

The patent uses dynamic switching of capacitors in and out of the circuit based on temperature ranges or measurement requirements. The switched capacitor circuit can dynamically adjust its effective capacitance value by connecting or disconnecting different capacitor elements, allowing the reference resistance to be adapted for different measurement conditions without requiring multiple fixed resistor values.