Managing Power Electronics: VLSI and DSP-Driven Computer Systems

Chapter 3

Circuits

Modern circuit design is a “mixed signal” endeavor thanks to the availability of sophisticated process technologies that make available bipolar and CMOS, power and signal, and passive and active components on the same die. It is then up to the circuit designer's creativity and inclination to assemble these components into the analog and/or logic building blocks necessary to develop the intended system on a chip. While the digitalization of traditional analog blocks continues, new analog blocks are invented all the time. Examples of new analog functions are charge-pump voltage regulators, MOSFETs, and LED drivers. A contemporary example of digital technology cutting deep into analog core functions is the digitalization of the frequency compensation in the control loop of switching regulators. In this case while the feat has been accomplished—and it can indeed be exhilarating to move poles and zeros (see glossary) around with a mouse click—it is not clear that the feature of digital frequency compensation, and its associated cost in silicon, is always justified. So while digital technology—circuits and processes—continues to gain ground, analog keeps reinventing itself and rebuilding around a central analog core of functions that is tough to crack. We don't expect to see the digitalization of an analog circuit like the band-gap voltage reference—namely a digital circuit taking the place of the current analog one—happening any time soon. In this section we will ...