VLSI is an acronym, it stands for Very Large Scale Integration. An integrated circuit or chip has millions of transistors. The foundry provides a library with cells that combine those transistors into a logic gate. Back-end engineers connect up those gates to make the actual silicon circuit layout, a VLSI design. Now, VLSI has a few sub-categories:
- Development of the technology itself, for example, tech node 16nm.
- Digital design, for example, an Intel CPU for desktop computers.
- Analog design, for example, an amplifier chip.
- Mixed-signal design, for example, a stepper motor driver.
Digital VLSI design
Digital IC design uses a cell library from a technology node. It will offer gates and flops, simply put. These are predefined gates that implement logic cells like AND, NOT and OR. In the past, a digital design went through schematic entry, connecting cells together by hand to make boolean logic. When chips started to become more complex, thousands of gates, a syntax developed to describe the behavior of a logic function. It is an abstraction layer where the designer has less control over the actual implementation. An EDA tool translates the syntax into cells. And so the HDL, hardware description language, was born.