A Tiq Based Cmos Flash A/d Converter for System-on-chip Applications

The analog-to-digital converter (ADC) is an essential part of system-on-chip (SoC) products because it bridges the gap between the analog physical world and the digital logical world. In the digital domain, low power and low voltage requirements are becoming more important issues as the channel length of MOSFET shrinks below 0.25 sub-micron values. Moreover, SoC trends force ADCs to be integrated on the chip with other digital circuits. These trends present new challenges in ADC circuit design. Thus, this thesis is to investigate high speed, low power, and low voltage CMOS flash ADCs for SoC applications. The proposed ADC utilizes the Threshold Inverter Quantization (TIQ) technique that uses two cascaded CMOS inverters as a comparator. The TIQ technique has been introduced in [53]. The TIQ technique proposed here has been developed for better implementation in SoC applications. Four issues are addressed to achieve high speed, low power consumption, and low voltage operation in the TIQ flash ADC. First, the high speed and low power TIQ flash ADC architecture is presented along with an optimal design method-called the systematic size variation (SSV) technique-for reducing the impacts of the process variation. Second, a new digital encoder called the fat tree encoder is introduced. The fat tree encoder replaces the ROM type encoder that is the speed bottleneck. Next, for low power applications, a power and resolution adaptive flash ADC (PRA-ADC) and a power management method in the TIQ flash ADC are presented to reduce/manage power consumption. Finally, a new voltage comparator, called the iv Quantum Voltage (QV) comparator, for next generation deep sub-micron low voltage CMOS flash ADC is proposed. In addition to the above four issues, simulation results and fabrication results of the TIQ flash ADC are discussed. The preliminary results show that the TIQ flash ADC achieves high speed, small size, low power consumption, and low voltage operation compared to other ADCs.