In an embodiment, a phase interpolator (PI) circuit is in an integrated circuit with a test latch, and the test latch is enabled by a test clock signal to under-sample the PI output clock signal from the signal source. In a method of operation, a PI output clock signal is generated in an integrated circuit, and the PI output clock signal is under-sampled in a test latch in the integrated circuit triggered by a test clock signal. Output data from the test latch is transmitted to a test device that is separated from the integrated circuit.
