Application Specific Integrated Circuits

ASICs (Application Specific Integrated Circuits): Technological Characteristics and Design Goals

ASIC, or Application Specific Integrated Circuit, refers to a type of integrated circuit that is specifically designed and manufactured to meet the requirements of a particular application. ASICs offer the advantage of tailored functionality, allowing users to specify the circuit’s design and configuration options. It’s essential to distinguish ASICs from ICs where the functionality is solely controlled by software, as ASICs are designed to perform specific hardware functions.

Here’s a classification of monolithically integrated circuits:

1. Standard ICs: These include common components like operational amplifiers (analog), TTL and CMOS Logic ICs (digital logic), microprocessors, RAM, and ROM.
2. ASICs: ASICs come in various forms, including Field Programmable Gate Arrays (FPGAs), Gate Arrays, Macro Cell ICs, Standard Cell ICs, and Full Custom ICs. They are tailored to specific applications and often offer higher performance or lower power consumption compared to standard ICs.

The distinction between standard ICs and ASICs can sometimes be blurry. An ASIC that gains popularity and sells in large numbers may eventually become a standard IC. Additionally, the classification between ROM (Read-Only Memory) and FPGA (Field-Programmable Gate Array) is not always straightforward.

Technological Characteristics of ASICs

Several technological characteristics highlight the dynamic progress in the field of ASICs:

1. Feature Size (λ): Feature size represents the smallest length of a MOS transistor or the minimum allowable distance between two connection lines on the chip. Smaller feature sizes reduce the required chip area, and improve transistor performance, but also increase manufacturing complexity.
2. Die Size: The silicon chip, or die, can vary in size from a few square millimeters to several square centimeters. Smaller feature sizes allow more transistors to be integrated into a single IC.
3. Complexity: The complexity of an IC can be measured in gate equivalents, with one gate equivalent equivalent to a NAND gate with two inputs. Advances in technology enable the integration of more transistors, leading to higher complexity and functionality in ASICs.

Design Goals for ASICs

When designing ASIC-based systems, several key goals come into play:

1. Cost-Effectiveness: ASICs should provide a cost-effective solution for the intended application.
2. Low Design Effort: The design process should be efficient in terms of time and cost.
3. High Performance: ASICs should offer superior functionality and speed.
4. Low Power Dissipation: Efficient power management to minimize energy consumption.
5. Compact Size and Weight: ASICs should enable small and lightweight system designs.
6. High Reliability: Ensuring the circuit operates reliably over time.
7. Low Mounting and Testing Costs: Minimizing expenses related to assembly and testing.

Meeting these design goals often involves trade-offs. For example, achieving higher performance may require a more significant design effort and result in increased power dissipation. Careful consideration of these trade-offs is essential to create ASICs that effectively meet the requirements of specific applications.

The Semiconductor Industry Association (SIA) provides roadmaps and specifications for semiconductor technology, indicating advancements in integration density, performance, and packaging. These advancements drive the development of more complex and cost-effective ASICs.

In summary, ASICs are custom-designed integrated circuits tailored to specific applications, offering a range of advantages over standard ICs. Achieving design goals for ASICs involves optimizing design styles based on factors like the expected production volume, design time, and desired performance. Cost-effectiveness remains a critical consideration in ASIC design and manufacturing.

What are some examples of standard ICs, and how do they differ from ASICs?

Examples of standard ICs include operational amplifiers (standard analog), TTL and CMOS Logic ICs (standard logic), microprocessors, RAM, and ROM. Standard ICs are not customized for a specific application and are typically designed for general-purpose use. ASICs, on the other hand, are tailored to specific applications.

What technological characteristics are important in the field of ASICs?

Technological characteristics in ASIC design include the “feature size,” which measures the size of the smallest MOS transistor or the minimum allowable distance between connection lines on chips. Smaller feature sizes reduce the required chip area and improve transistor performance but also make manufacturing more demanding. The size of the silicon chip (die) varies in area and affects the number of transistors that can be integrated into an IC.

How is the complexity of an IC measured?

The complexity of an IC can be measured by the number of gate equivalents, where one gate equivalent is equivalent to a NAND gate with two inputs. This metric helps assess the level of complexity and functionality of an IC.

What are some key design goals for ASICs?

Key design goals for ASICs include cost-effectiveness, low design effort in terms of time and cost, high performance (functionality and speed), low power dissipation, small volume and weight, high reliability, and low costs for mounting and testing. ASICs offer advantages in achieving these goals compared to standard ICs.

What factors influence the choice of design style in ASIC design?

The choice of design style in ASIC design depends on factors such as the expected number of parts, design time, and desired performance. Different design styles have trade-offs between design effort, performance, and other goals. The selection of the optimal design style is influenced by the specific requirements of the system environment.