Effects of packaging and process spread on a mobility-based frequency reference in 0.16-μm CMOS

In this paper, we explore the robustness of frequency references based on the electron mobility in a MOS transistor by implementing them with both thin-oxide and thick-oxide MOS transistors in a 0.16-μm CMOS process, and by testing samples packaged in both ceramic and plastic packages. The proposed low-voltage low-power circuit requires no off-chip components, making it suitable for applications requiring fully integrated solutions, such as Wireless Sensor Networks. Over the temperature range from -55°C to 125°C, its frequency spread is less than ±1% (3σ) after a one-point trim. Fabricated in a baseline 0.16-μm CMOS process, the 50 kHz frequency reference occupies 0.06 mm² and, at room temperature, its consumption with a 1.2-V supply is less than 17 μW.