In order to achieve a high level of integration it is often necessary to consider a semi-custom chip solution. The type of approach will depend upon complexity of the circuit, whether the design is purely digital, analogue or a mix. Today the volume of devices required will also have a major impact. The latest technology and the highest levels of integration do not come cheap. The tooling charges which some ASIC’s require are over £100k.

 

If the volumes required are not so large then a multi-project wafer should be considered. The design shares space on a wafer with other peoples. The advantage is shared and therefore reduced tooling costs. The disadvantage is time as MPW’s are normally manufactured a limited number of times per year.

 

FPGA’s are excellent for rapid design turnaround and low to medium volumes. However as the volumes increase it becomes more cost effective to switch to a custom solution as, by their very nature, FPGA’s are not optimised and will contain redundant silicon. An FPGA to ASIC conversion solution provides an easy upgrade path.

 

Mixed signal designs often give the best price / performance benefits in semi-custom designs. Often used at the frond end of systems for sensor monitoring, signal conditioning etc, it is where the size and high level of integration is most required.

Depending on the application and requirements a specific technology needs to be selected. This information is available in the form of a library from the Silicon Foundry.

Chip Design