Self-Assisted Logic Testing
Original Publication Date: 1986-Sep-01
Included in the Prior Art Database: 2005-Mar-09
During the manufacturing process for logic chips, a number of problems can occur that could make these chips defective. Some of these problems cause DC defects; testing methodologies for detection of these are widely used throughout the industry. However, some of these problems can cause AC defects. That is, the logic will function correctly, but slower than it should. Inexpensive testing methodologies for this case are not common. This article describes such a methodology, implemented by circuitry added to the logic chip to assist in testing itself. The diagram shown in Fig. 1 illustrates a way to design a logic chip so that AC testing can be performed using signals at a DC rate only, external to the chip. If not already present in the design, latches are added at the inputs (LI) and outputs (LO) of the chip.