Design of a built-in current sensor for IDDQ testing

摘要

IDDQ testing can cover the traditional stuck-at-faultsnas well as other defects that may affect reliability. One of the mostncritical issues in IDDQ testing is a built-in current sensorn(BICS) that can be used to detect abnormal static currents. The mostnserious problem in the conventional current sensor is performancendegradation. The purpose of this work is to present an effective BICS,nwhich has a very small impact on the performance of the circuit underntest (CUT). The proposed BICS works in two-modes, the normal mode andnthe test mode. In the normal mode, our BICS is totally isolated from thenCUT. Thus there Is absolutely no performance degradation of the CUT. Innthe testing mode, our BICS detects the abnormal current caused bynpermanent manufacturing defects. Furthermore, the BICS requires neithernan external voltage reference nor a current source. Hence, the BICSnrequires less area and is more efficient than the conventional currentnsensors. The validity and effectiveness of the proposed RIGS arenverified through the HSPICE simulation and the chip test. Thenfabrication was done through “CMPSC8” 0.8 Μm n-wellnprocess. The testing results show that our BICS operates at a speed ofn25 MHz