Developments in transient response analysis

The benefits of transient response analysis (TRA) as a generic functional test technique for linear macros in mixed-signal systems is well documented. The simple logic amplitude test stimuli that are employed can be propagated through neighbouring digital circuitry or injected via a digital scan path. The resultant excitation is the convolution of the input stimulus and the macros transfer function and details the macros functionality in the time domain. A number of analysis techniques for the comparison of observed and expected transient responses have been developed. These techniques generate a single figure termed the index of functionality, which is an absolute measure of how closely the observed response matches the expected response and permits functional comparisons of devices. The main advantage of this type of test in mixed-signal systems is the ease with which the simple stimuli can be applied to the input of the linear macro under test. Hence nodal controllability is generally not a problem and a considerable part of the test problem is solved. However, if the macro under test is deeply embedded then the access to the resulting response can be a problem. The aim of this paper is to detail a preliminary investigation into the effects of the sampling and quantizing transient responses for extraction via a digital scan path as a way of overcoming this observability problem