The symbol IDDT has a double meaning. IDDT is used to refer to the transient (or dynamic) supply current and IDDT is also used to refer to a test method that is based on taking transient supply current (IDDT) measurements.
IDDT testing is the counterpart of IDDQ testing and is based on the observation that a proper working circuit draws a lot of current at the moment that it changes from one state to another. This part of the supply current is called the switching or transient current. The T in the IDDT symbol refers to the transient part of the supply current. Using the switching or transient current as source of information to differentiate between good and defective circuits has only recently been the subject of various research activities, exploring the use of this parameter as a counterpart to the IDDQ parameter.
IDDT testing is a test technique based on measuring the Transient (or dynamic) supply current of the device under test. IDDT measurements are done when the circuit under test is active, opposite to the IDDQ approach, where the measurement is taking place when the circuit is in a quiescent or stable state. The IDDT decision criterion is based on combining one or more parameters extracted from the current waveform observed. Typical parameters that are looked at or the peak values, pulse with values, the average current (either of the transient part of the current waveform or of the complete current waveform) or of the charge related to period that current waveform is observed. The latter parameter provides a lot of information regarding the proper switching of the circuit observed.
A large number of publications exists that deal with IDDQ, ISSQ and IDDT technology, that address the application of these technologies or that discuss the use and application of IDDX measurement modules.
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