资 源 简 介
ICs are made on a wafer. Circuits are built up with successive mask layers. The number ofmasks used to define the interconnect and other layers is different between full-customICs and programmable ASICsFull-Custom ASICsAll mask layers are customized in a full-custom ASIC.It only makes sense to design a full-custom IC if there are no libraries available.Full-custom offers the highest performance and lowest part cost (smallest die size) with thedisadvantages of increased design TIme, complexity, design expense, and highest risk.Microprocessors were exclusively full-custom, but designers are increasingly turning tosemicustom ASIC techniques in this area too.Other examples of full-custom ICs or ASICs are requirements for high-voltage (automobile),analog/digital (communicaTIons), or sensors and actuators.
Standard-Cell–Based ASICs
A cell-based ASIC (CBIC—“sea-bick”)• Standard cells• Possibly megacells, megafuncTIons, fullcustomblocks, system-level macros (SLMs),fixed blocks, cores, or FuncTIonal StandardBlocks (FSBs)• All mask layers are customized—transistors andinterconnect• Custom blocks can be embedded• Manufacturing lead time is about eight weeks.
