I first became familiar with PLLs by working for National Semiconductor as an applications engineer. While supporting customers, I noticed that there were many repeat questions. Instead of creating the same response over and over, it made more sense to create a document, worksheet, or program to address these recurring questions in greater detail and just re-send the file. From all of these documents, worksheets, and programs, this book was born. Many questions concerning PLLs can be answered through a greater understanding of the problem and the mathematics involved. By approaching problems in a rigorous mathematical way one gains a greater level of understanding, a greater level of satisfaction, and the ability to apply the concepts learned to other problems. Many of the formulas that are commonly used for PLL design and simulation contain gross approximations with no or little justification of how they were derived. Others are rigorously derived, but from outdated textbooks that make assumptions not true of the PLL systems today. It is therefore no surprise that there areso many rules of thumb to be born which yield unreliable results. Another fault of these formulas is that many of them have not been compared to measured data to ensure that they account for all relevant factors. There is also the other approach, not trusting formulas enough and relying on only measured results. The fault with this is that many great insights are lost and it is difficult to learn and grow in PLL knowledge this way. Furthermore, by knowing what a result should theoretically be, it makes it easier to spot and diagnose problems with a PLL circuit. This book takes a unique approach to PLL design by combining rigorous mathematical derivations for formulas with actual measured data. When there is agreement between these two, then one can feel much more confident with the results. The fourth edition of this book adds a lot of information about partially integrated loop filters and oscillators, as well as cleaning up some minor mistakes in the third edition.
