Metody obniżania poboru mocy podczas testowania wewnątrzukładowego

W referacie przedstawiono wyniki badań nad obniżeniem rozpraszanej mocy generatora pseudolosowych wektorów testowych i analizatora sygnatur, które są wykorzystywane podczas wbudowanego samotestowania urządzeń cyfrowych BIST (ang. Built-In Self-Testing). Zaproponowano nową strukturę układu, która pozwala obniżyć moc wydzielaną w trakcie przeprowadzania samotestowania. Główna idea opiera się na takiej modyfikacji elementów BIST, w której zamiast przerzutników -D wykorzystuje się przerzutniki -T.

Nowadays during organizing built-in self testing the most spread and best known are scan design techniques based on the full or partly scanning path. The first testing vector is put into testing system by SP (Scanning Path) data. Shifting information takes place during clock pulses, and the number of shifts is equal to the number of flip-flops in SP. Then, one synchronization pulse is used to write system changes in adequate SP positions. Next, SP values are applied to the output of the circuits, and at the same time on the date input SP follow next testing vector. So, if the SP is built of k-elements, there are needed k+1 clock pulses to put one testing vector. This realization is non effective because of high power consumption. Firstly, in modern BIST systems there are used many D-flip flops (memory elements). Even when there are used many SPs, the number of positions in each SP can reach a few thousands. In this case to put a new testing vector it is necessary to use a few thousand of synchronization pulses. Simultaneously the high amount of energy is needed, because each new testing vector needs one synchronization pulse. Secondly, during shifting data in SP in a testing circuit there are empty switchings, which requires energy. So, to minimize the power consumption test-per-clock technique is used. In this paper the new idea of minimizing power dissipation in BIST with test-per-clock technique is presented. The main idea of the new solution is to stop putting synchronization pulses to flip-flops in which their state has not changed in the current synchronization pulses. It will allow eliminating not necessary switching activity in BIST and, what is more, it will allow to decrease power consumption and Weighted Switching Activity.