Degree Type


Date of Award


Degree Name

Doctor of Philosophy


Electrical and Computer Engineering

First Advisor

William C. Black, Jr.


Moore's law not only applies to the semiconductor technology, it also applies to the Hard Disk Drive (HDD) system in the last 35 years. In order to meet the emerging demands of high performance computing application, HDD will continue to evolve in a very rapid pace. Very high speed analog-to-digital converters are demanded for Hard Disk Drive application.;FLASH architecture provides the highest speed using 2n-1 comparators to perform an n-bit conversion. In the extremes of speed, however, exotic technologies must still be used to achieve conversion rates beyond those obtained with a conventional silicon implementation. In this research, a four-way, time-interleaved flash ADC is demonstrated to achieve conversion speed up to 900MS/s using a 2.5v digital 0.25 micron bulk CMOS process. The maximum conversion rate practical with any technology is extended by the use of an array of well-matched flash ADCs. This technique trades off increased die area for increased speed in nearly one for one relationship but an reduced performance if the ADCs are not well matched in terms of gain, offset, nonlinearities and sampling skew. In the approach considered here, these problems are minimized by use of a simple method that ensures the individual ADC gain, offset and nonlinearities characteristics are inherently almost identical. A simple four phase clock generator is demonstrated which introduces only a small sampling skew. This scheme has been demonstrated in the comparatively simple 6-bit flash ADC case which achieved the highest acquisition speed of 900MS/s. Compared with the prior works, our work achieves higher SNDR at much higher analog input frequency at sampling frequency of 900MS/s. This same scheme may be applied to the first n-bits of a pipeline converter (or other converter method) enabling the same identical performance in the most significant bits.;In the second part of this dissertation, a new calibration principle with Voltage Controlled Resistors (VCR) for matched current sources is proposed. This technique can be used to produce multi copies of current units. Therefore, it is suitable for the calibration of high-resolution digital-to-analog converters that are based on equal current sources.



Digital Repository @ Iowa State University,

Copyright Owner

Baiying Yu



Proquest ID


File Format


File Size

121 pages