Fully Integrated CMOS Noise Thermometer
Dennis Kaandorp · Research Repository (Delft University of Technology) · 2020
Temperature sensors are integrated into virtually all electronic devices. Unfortunately, the accuracy of commonly used temperature sensors greatly deteriorates in more advanced CMOS processes, thus requiring a certain amount of calibration. Thermal noise thermometry is a highly accurate niche temperature sensing method. It employs the thermal noise of a resistive component to determine the temperature. Thermal noise thermometry is a primary temperature sensing method that is inherently accurate and perfectly linear with temperature, which is ideal for temperature sensors. The fundamental nature of thermal noise with virtually no requirements for accurate device characterization is excellent for integration in any advanced technology. The primary disadvantage of noise thermometers is that they are inherently slow, their resolution improves with longer measurement duration and/or wider measurement bandwidth due to the stochastic nature of noise thermometers, which is why these sensors are rarely used outside of laboratory environments.Although many discrete noise thermometers have been developed in the past, limited research has been conducted on integrating a noise thermometer on a chip. Integrated noise thermometry has the potential to overcome the long measurement times of existing noise thermometers by giving access to increased measurement bandwidths of integrated circuits, as there is no need for off-chip components.Since thermal noise is typically a small signal, the readout is extremely sensitive to non-idealities, such as excess circuit noise and parasitic capacitances. These non-idealities must be properly taken into account or be compensated in order to perform accurate temperature measurements. This thesis compares many different compensation techniques to increase the accuracy of integrated noise thermometry and presents a new method for compensating noise thermometry error sources. This new method greatly simplifies the overall design and theoretically removes all non-idealities of the readout electronics, such as amplifier noise, from the temperature reading. Circuit simulations of this technique demonstrate the viability of the proposed method by showing that >97 of the errors caused by the readout noise and parasitic capacitance can be compensated. The presented methods will allow for accurate noise thermometry to be implemented in advanced CMOS processes and thereby increase the speed and application possibilities of noise thermometry.