Have you ever designed a clock circuit where you did something just because it had been

　　done that way in the past？ Or have you ever used a particular part without knowing why

　　purely because it was on another design？ This happens quite often with today’s designs，

　　particularly with clock generation and distribution circuits.

　　This book has been written by engineers for engineers who want to design clock circuitry

　　using the best methods. Its focus is on the practical implementation of clock generation

　　and distribution circuits for use in high-speed digital designs. This material was gathered

　　from many time-tested designs， as well as from new techniques learned to address th

　　needs for faster clock frequencies.

　　The ultimate goal is to have clean， solid clocks. Many companies now employ full

　　departments dedicated to signal integrity. They perform simulations， design reviews， and

　　a variety of analyses to ensure the best operation of the clock. There are several factors

　　designers need to consider that affect the clock waveform. This book will address many of

　　these key design issues for clocks.

　　Clock generators play a key role in designs today. In the pursuit of high-speed， many

　　systems have adopted synchronous design styles. With this methodology comes the need

　　for a variety of frequencies and many copies of the same clock. In most systems， these

　　clocks need to be in phase with one another. If they are not， precious cycle time is lost

　　Skew between clocks becomes very important in keeping all of the devices operating at

　　their peak rates. Specialized clock buffers have led the way in providing clean， accurate

　　clock signals.