Design of a built-in current sensor for IDDQ testing

I_DDQ testing can cover the traditional stuck-at-faults as well as other defects that may affect reliability. One of the most critical issues in I_DDQ testing is a built-in current sensor (BICS) that can be used to detect abnormal static currents. The most serious problem in the conventional current sensor is performance degradation. The purpose of this work is to present an effective BICS, which has a very small impact on the performance of the circuit under test (CUT). The proposed BICS works in two-modes, the normal mode and the test mode. In the normal mode, our BICS is totally isolated from the CUT. Thus there Is absolutely no performance degradation of the CUT. In the testing mode, our BICS detects the abnormal current caused by permanent manufacturing defects. Furthermore, the BICS requires neither an external voltage reference nor a current source. Hence, the BICS requires less area and is more efficient than the conventional current sensors. The validity and effectiveness of the proposed RIGS are verified through the HSPICE simulation and the chip test. The fabrication was done through “CMPSC8” 0.8 μm n-well process. The testing results show that our BICS operates at a speed of 25 MHz