© 2018 IEEE. A boundary scan design with embedded time-to-digital converter (TDCBS) has been proposed for testing small delay faults. In this paper, the TDCBS is applied for testing TSVs in 3D IC. To reduce test application time of the TDCBS, we propose a modified TAP controller that utilizes the bypass mode for reducing unnecessary scan shifts during observation of the captured results. The simulation for an experimental circuit is shown to evaluate the effectiveness of the proposed method.