Design of PVT Compensated Resistance to Frequency Converter for Sensor Array Applications

Abstract

The thesis presents a new CMOS resistor to frequency read-out circuit to be used in resistive sensing applications. Resistive sensing is used in different applications like temperature sensing, force sensing, and light sensing. An accurate read-out circuit is needed to detect the resistance value for the on-chip sensor. The existing techniques suffer from PVT (process, voltage, temperature) variations or require a large silicon chip area. In this thesis, we propose a new technique to sense the sensor resistance in a simple, accurate, and efficient manner. First, we present the open-loop Schmitt Trigger based relaxation oscillator that converts the resistance value to a frequency in the output waveform. A more accurate implementation that compensated PVT variations is also presented based on closed-loop configuration using a switched capacitor resistor, operational amplifier integrator, and a voltage-controlled oscillator. The design is implemented and fabricated using TSMC 180nm CMOS technology. The chip-level power supply for the proposed circuit is 1V. This thesis presents the detailed designs for critical components, layout design, and testing PCB design. Also, this thesis includes the simulation and the testing results for the proposed circuit.