Gate Array ASIC

Comparing the available solutions for customised logic, such as standard cell ASIC or FPGA, Gate Array offers one of the best balanced options in many parameters. Though it is not always the best in every respect, the Gate Array is the product of choice for many general purpose requirements. Gate Arrays provide a wide range of package options and high reliability, offering one of most flexible ASIC in all semi-custom devices.

Further advantages of Gate Array ASIC technology obviously are in the low NRE costs and in the fast time to market. With only the metallisation layers used for customization, Gate Arrays NRE costs are many times cheaper than comparable standard-cell ASICs. The design flow for Gate Array ASICs relatively simple, most steps can be standardised. Nevertheless, Gate Array ASICs have many advantages compared to FPGAs. Typically Gate Arrays are cheaper than FPGAs, while the are more power-efficient and can achieve higher operating speeds.

One advantage of Gate Array technology compared to Standard Cell ASIC designs is the relatively low minimum order quantity. This enables users with low volume requirements and tight cost constraints to realise ASIC solutions. A typical range of applications include computer, communication, industry and office automation products.

Gate Array ASICs are based on the concept of a GATE, typically formed by two N-channel and two P-channel transistors. The digital logic function is realised by connecting these gates using metal or poly interconnect. This way only few masks are required to form e.g. NAND or NOR gates. More complex functions are composed by using multiple gates. Memory blocks can be formed by using the available transistors, but the efficiency is not as good as Embedded Array technology

Two major types of Gate Arrays exist:

A traditional (Channeled) Gate Array or a Sea-of-Gate GateArray. The difference is that in a aea-of-gate structure the gates fill all core area, while in a channel gate array, dedicated routing channels separate the regular gate structures. In sea-of-gates the routing is performed over the gates, hence more metal layers are typically required, but the gate density is much higher than in a channel gate array.

Fujitsu offers Sea-of-Gate Arrays for following technologies:

• CG46
• CG61P