Testing integrated circuit designs containing multiple phase rotators

A circuit for testing a plurality of phase rotators, comprising:

• a compare element comprising a phase detector including a first input and a second input, wherein the compare element is configured to compare a first phase of a first signal provided at the first input to a second phase of a second signal provided at the second input;
• a first test bus connected to the first input of the phase detector;
• a second test bus connected to the second input of the phase detector;
• a phase locked loop (PLL) including a first input of the PLL, a second input of the PLL, and an output to generate a PLL phase to the first test bus;
• a reference clock which inputs a phase shift into the first input of the PLL;
• and
• a test phase rotator coupled between the second input of the PLL and the output of the PLL and which provides a feedback phase of the PLL,
• wherein a phase source separate from the PLL and comprising one of the plurality of phase rotators is selectively connected to the second test bus.