High-Speed CMOS MCML Basic Cells And Thermometer Decoder Circuit Design

The Digital-to-Analog Converter (DAC) is a significant module in the moderncommunication systems. With the rapid development of Semiconductor IntegratedCircuit technology, the DAC design has headed with higher in speed and lower in powerdissipation. However, currently most of the mainstream high-speed and high-accuracyDAC is designed to use in CMOS logic, and a major drawback of this logic is that thedynamic power consumption vary with the changing of frequency. Compared with it,MOS Current Mode Logic (MCML) has a constant static current, and itsdynamic power consumption keeps constant since the frequency has changed. ThereforeMCML is a very promising technology approach in the high-speed low-power DACdesign.This thesis takes MOSFET model as the starting point to provide the MCMLcircuit equivalent models and parameters. Furthermore, the thesis uses the previoustheory to summarize an MCML design process, and applies this method to design theMCML basic cells and thermometer decoder circuit. The thesis makes it as a part of thedigital coding which is applied in a16bit current-steering DAC chip. The DACsampling clock frequency is1GHz, its segmented structure is6+5+5, while the6mostsignificant bits and the5intermediate significant bits are thermometer code, and the5least significant bits are binary-weighted code.This thesis is based on SMIC0.18μm1P6M standard CMOS process. PowerSupply is1.8V. With the output swing0.5V, the static current50μA and loading theinput signal500MHz and clock signal1GHz, the thesis based on Cadence environmentto use Spectre to make a simulation and the simulation results show that, the delays ofMCML inverter and logic gate and latch are12.76ps and45.09ps and60.16psindividually，and the thermometer decoder circuit which designed can meet thefunctional requirements. Its power is50.13mW which keeps a constant since thefrequency has changed. Considering matching and antenna effect and reducing of thesubstrate noise, the layout of MCML basic cells and thermometer decoder circuit hasbeen given.