What is Design For Testability And Why Is It Important?

As advances in integrated circuit (IC) processing technology continue to minimize the feature size, more sophisticated chips are being planned, developed, and manufactured. With increased complexity, comes a rise in possible testing issues. A very large-scale integrated (VLSI) circuit may contain multiple internal circuit nodes that cannot be operated or viewed directly from the chip’s input/output pins. The process of ensuring that no flaws are concealed deep inside a VLSI circuit can be daunting, and the time and effort spent on testing bugs can greatly increase the cost of IC testing and thereby overall chip cost. Hence, design for testability approaches tries to lower the significant cost in time and effort necessary to construct test vector sequences for VLSI  circuits. If the chips are built for testability, identifying problematic chips can be substantially simpler. 

VLSI courses

What is Design For Testability in VLSI?

In VLSI design, Design for Testability (DFT) is an approach that aims to make digital circuits easier to test during the manufacturing and debugging process. DFT in VLSI design involves incorporating additional circuitry and design features such as scan chains, built-in self-test (BIST) circuits, and boundary scan cells into the chip design to facilitate testing. Design for testability in VLSI design is essential to ensure that the fabricated chips are free from any kind of manufacturing defects. It also reduces the overall test time and thereby the cost of testing, and debugging. By incorporating DFT techniques into the chip design, it becomes easier to test the structural correctness of the chip, leading to higher-quality products and faster time-to-market.

Why is Design For Testability Important in VLSI?

Design for Testability (DFT) is essential in VLSI (Very Large Scale Integration) design because:

  1. By designing a chip with testability in mind, it becomes easier to identify the structural defects in the chip and fix design errors before the product is shipped to customers. 
  2. Designing a chip with built-in testability features can make the testing process more efficient, reducing the cost and time required for testing. This can lead to significant cost savings during the manufacturing process.
  3. By incorporating DFT features into the chip design can help to identify any defects early in the process, allowing for faster repairs and improvements in production yield.
  4. Design for testability can help accelerate the development cycle by reducing the time and effort required for testing and debugging. 
  5. DFT can make it easier to diagnose and fix problems in the chip design, reducing the effort required for maintenance and updates.


DFT is critical for VLSI design as it enables designers to create chips that are more reliable, easier to test, and more efficient, ultimately leading to higher-quality products, lower costs, and faster time-to-market. If you want to know more about DFT in VLSI or want to make a career in the semiconductor industry, Chipedge has got you covered. It is the best VLSI training institute that offers various VLSI courses online including DFT Course, RTL Design, VLSI Physical Design Courses, etc. Contact us to know more.

Image Credits