DFT for embedded charge-pump PLL systems incorporating IEEE 1149.1

In this work we present a DFT strategy to test embedded Charge-Pump Phase Locked Loops (CP-PLL) in systems incorporating boundary scan, wherein the proposed DFT allows the verification of the operating frequency range of the CP-PLL while the system is in test mode. This is achieved with a minimal degradation in PLL performance, with lock characteristics remaining unchanged. Simulation results with the layout extracted netlist of the CP-PLL are used to illustrate the working of the technique.