Low-Voltage CMOS Design Fundamentals

This Chapter reviews the MOS transistor device properties with particular focus on operation with limited voltages, including weak inversion operation, and body terminal usage. Thereby, benefits are presented as well as the critical performance trade-offs are discussed. A further part shows power switch design in the context of low drive voltages and with the constraints of a minimum current flow. Further on, concrete design of basic circuits as well as corresponding design guidelines are explained in Chap. 4 by using the here introduced basics. Process Selection Based on the given requirements for meeting the aimed specifications derived in Chap. 2 selection of an appropriate CMOS fabrication process needs to match to the following criteria: voltage range: MOSFET threshold voltage and maximum voltage ratings additional primary devices: e.g. on-chip metal-insulator-metal (MIM) capacitors, Schottky diodes, and the possibility of variable process options, e.g. high resistive poly-silicon devices or thick-metal layers order terms and conditions: area restirctions, accessibility, rules, and costs Therefore, a 0.35\(\upmu \)m CMOS 4-metal (4M2P) process has been chosen from X-Fab. In particular, this process technology offers a wide supply voltage range, i.e. low-voltage operation while allowing also high supply voltages (high \(V_\text {buf}\)) is an essential issue. This CMOS process technology offers a low threshold-voltage option, the core cells can deal with voltages of 3–5 V, and it provides metal-insulator-metal capacitors, high-resistive poly-silicon layers, Schottky diodes, and even high-voltage options. Thus, the designed integrated circuits can be optimized for supply voltages below 1 V while taking advantage of the various options. Further details are in Appendix D.2.