Iddq – current-based – testing involves making precision, non-intrusive measurements of the current drawn by the device-under-test to reveal defects in integrated circuits. It relies on measuring the supply current (Idd) in the quiescent state (when the circuit is not switching and inputs are held at static values). The current consumed in the state is commonly called Iddq for Idd (quiescent) and hence the name.
A survey has recently been carried out by Q-Star Test (Brugge, Belgium) of engineers, managers and technical personnel involved in the design, the implementation of design-for-test (DFT) and the creation and running of comprehensive test programs on ICs
The survey found that 83 percent of the respondents are familiar with Iddq testing methods and of the group that provided information on how Iddq is embedded in their company flow indicated that 64 percent had Iddq testing as part of the DFT flow while 77 percent said that Iddq is part of the test flow.
85 percent of those familiar with Iddq said the primary reason for applying this testing method is to meet quality requirements, and to meet equirements imposed by standards such with 39 percent citing the automotive AEC Q-100 standard.
In addition to meeting quality requirements, another major driver is to reduce overall test time, as reported by 22 percent of those knowledgeable of Iddq. The survey indicated that 75 percent of the test applications, of which data was provided, have Iddq test times exceeding 0.1 second per part, and 40 percent longer than 0.5 seconds per part.
Among automated test pattern generation (ATPG) tools used to generate Iddq test vectors, the market is fragmented. Of the known cases 32 percent of the users uses Mentor Graphics tools, 31 percent utilizing Synopsys tools, 9 percent Cadence tools and a mixture of tools by the rest.
Despite speed and accuracy limitations of conventional ATE platforms, Q-Star Test says ATE embedded resources are commonly applied for these measurements, although 66 percent indicated that they are open to a more accurate and faster interface-board based solution.