Design For Testing

Design For Testing

Design for Test (aka "Design for Testability" or "DFT") is a name for design techniques that add certain testability features to a microelectronic hardware product design. The premise of the added features is that they make it easier to develop and apply manufacturing tests for the designed hardware. The purpose of manufacturing tests is to validate that the product hardware contains no defects that could, otherwise, adversely affect the product’s correct functioning.

Tests are applied at several steps in the hardware manufacturing flow and, for certain products, may also be used for hardware maintenance in the customer’s environment. The tests generally are driven by test programs that execute in Automatic Test Equipment (ATE) or, in the case of system maintenance, inside the assembled system itself. In addition to finding and indicating the presence of defects (i.e., the test fails), tests may be able to log diagnostic information about the nature of the encountered test fails. The diagnostic information can be used to locate the source of the failure.

In other words, the response of vectors(patterns) from a good circuit is compared with the response of vectors(using same patterns) from a DUT(device under test). If the response is the same or matches, the circuit is good. Otherwise, the circuit is faulty.

DFT plays an important role in the development of test programs and as an interface for test application and diagnostics. Automatic test pattern generation, or ATPG, is much easier if appropriate DFT rules and suggestions have been implemented.