Scan flip-flop with internal latency for scan input and its operation method

TLDR: In this paper, a scan flip-flop circuit with a multiplexer and a delay element is presented, which allows the selection of either the scan input or the data input for presentation at the input of the flipflop.

Abstract: A scan flip-flop circuit including a data input, a scan input, a data output, a flip-flop, a multiplexer and a delay element is provided. The multiplexer allows selection of either the scan input or the data input for presentation at the input of the flip-flop. The flip-flop provides an output signal at the output of the scan flip-flop. The delay element is in a signal path between the scan input and the input of the flip-flop, and provides a signal propagation delay between the scan input and the input of the flip-flop. The delay between the scan input and the input of the flip-flop is substantially larger than the signal propagation delay between the data input and the input of the flip-flop. The delay in the scan path reduces the need for external buffers to avoid hold-time violations during scan testing of integrated circuits.