5.1 LESSON FROM THE REAL WORLD: THE MANAGER’S PERSPECTIVE AND THE ENGINEER’S PERSPECTIVE
Designs are timing (and power and noise) closed to some set of operating conditions. Those operating conditions often include a nominal voltage (plus or minus some prescribed range) and some range of temperatures. In addition, for manufacturing purposes, a range of processing is also a factor in the timing, power, and noise closure process. Indeed, Chapter 8 will point out that the timing views are usually described as at a given “corner” representing a given process, voltage, and temperature (PVT).
On one communication channel design on which I worked while in the data-communications design center in a large microprocessor company, it was important to determine as soon after start-up at what voltage would the dev ice be operating. This is not a difficult issue to resolve. One could develop a solution circuit in several different manners. One possible solution is to use a voltage controller oscillator (VCO) that has a well-defined relationship between the operating voltage and the oscillator frequency with periodic reading based on some external clocking system of the number of toggles of the output indicating the voltage. Some complications involve the effect on the frequency by the process and temperature at which the circuit operates during the reading. Such complications can usually be overcome, however, mostly through semisignificant levels of analog circuit ...