PSRR measurement method for PLL including power delivery network

A measurement method to estimate PSRR (Power Supply noise Rejection Ratio) of PLL (Phase Locked Loop) using DPI (Direct Power Injection) method is proposed. The DPI (Direct Power Injection) method specified in IEC 62132-4. Through DPI measurement, PLL showed 50 dB to 60 dB PSRR in the 100 kHz ~ 20 MHz. The power noise level allowed by the DUT is predicted using the PSRR results. The phase noise was measured at various power sources such as LDO and DC-DC converters. These power noise levels are compared with allowable noise specification. PSRR level was improved with 1uF decoupling capacitor by 40dB in the range of 1 MHz ~ 10 MHz. The proposed method can provide guidelines on selecting a power source component of a clock generator and designing an efficient PDN (Power Delivery Network) structure.