Testing of an integrated circuit that contains secret information

Octrooi-Publicatie

Goel, S.K., Vranken, H.P.E., Marinissen, E.J., Nieuwland, A. & Vermeulen, H.G. (2008). Testing of an integrated circuit that contains secret information. Patent No. CN101238382.

Abstract

 

An integrated circuit (10) comprises a functional circuit (12a to c) that contain information that must be secured against unauthorized access. The integrated circuit comprises a test access circuit (14, 16) coupled to the functional circuit (12a to c), and a plurality of fuse elements (18) coupled to the test access circuit (14, 16). The fuse elements (18) are connected in a circuit configuration that makes the functional circuit (12a to c) consistently accessible via the test access circuit (14, 16) only when first fuse elements (18) of the plurality are in a blown state and second fuse elements (18) of the plurality are in a not-blown state. As a result the integrated circuit can be tested after selectively blowing all of the first fuse elements (18). After testing at least part of thesecond fuse elements (18) is blown.; As a result, a person that does not know which fuse elements are first fuse elements and which are second fuse elements is presented with difficulties to restore the integrated circuit to a state where test access with the danger of access to the secured information is possible.