Faculty of Engineering and Natural Sciences
Continuous Time Sigma Delta
Abstract: Deployment of OFDM based wide band communication standards such as WIMAX and WLAN combined with the continued pressure to scale and integrate in CMOS has brought up new challenges for the crucial ADCs and DAC circuits. Sigma Delta modulators have been popular for a long time in CMOS integrated circuits due to their immunity to process imperfections, low area and power consumption. The traditional switched capacitor (SC-SDM) based sigma delta ADCs have been successful in relatively narrow band width applications such as GSM, EDGE and audio. However their reliance on capacitor matching and the quality of the sampling amplifier is becoming a handicap in Nano-meter CMOS, especially when targeting wider band width applications. Continuous time sigma delta (CT-SDM) modulators are drawing attention due to their immunity to leakage and anti-aliasing filter build in the loop. A special breed of CT-SDMs is called Active-Passive sigma delta modulator (APSDM) has been introduced to the literature recently in 2003. In these, the loop filter is implemented using an amplifier and passive RC components. This seminar will briefly cover the history of mixed signal CMOS integration and continue with general CT-SDMs and finally focus on APSDM architectures.
Dr. Rahmi Hezar has received his Ph.D. from Georgia Institute of Technology in 2000 and has been working in the Nano-meter Integration branch of Wireless Business Unit in Texas Instruments as a member of technical staff. His initial work includes design of high speed digital decimation and interpolation filter architectures. He later has focused on development of continuous time sigma delta modulators for CMOS integrated wireless platforms that are now in many products. He holds 5 patents and several paper publications in this area. He is currently working on developing mixed signal systems for bio-medical applications.
July 13, 2007, 10:40, FENS G032