ACCURATE DYNAMIC I_DD TESTING AND LOCALIZATION OF DEFECTIVE PARTS IN MIXED-SIGNAL CIRCUITS
Vladislav Nagy - Viera Stopjaková
The dynamic supply current testing based on the measurement of voltage drop across a parasitic resistance of the supply voltage metal routing is presented. Auto-zero technique for voltage comparator offset cancelation, which provides very accurate and sensitive low voltage drop measurement across the sensing resistor is proposed. Therefore, the proposed sensor might be used as a current monitor for dynamic current testing of mixed-signal circuits without any additional element necessarily connected in series with the power supply line. In the proposed defect localization methodology, the mixed-signal chip is split into smaller blocks and each block is tested independently. Then the results are evaluated in the common control part, which provides the information about a defective part and shifts this data to a serial data output pin. Therefore, with only one additional pin we may exactly localize the defective part of the integrated system. A USB (universal serial bus) high side power distribution switch was used as an experimental mixed-signal device under test (DUT). The proposed current monitor together with the localization technique was implemented into a circuit under test and the whole experimental chip was designed in a standard 0.35μm CMOS technology. Finally, the feasibility and efficiency of the proposed test and localization methodology were evaluated and the obtained results are presented.
Keywords: built-in current sensor, IDD testing, mixed-signal circuits, auto-zero technique, low offset comparator, defect localization.