PDN Impedance Measurements using the Bode 500 and Picotest PDN Probes

by Florian Hämmerle - OMICRON Lab
The power delivery network (PDN) describes the complete system delivering the power from the power source (i.e. a battery or a AC/DC power supply) to the power sink (i.e. a processor or FPGA). The PDN must be able to provide a sufficiently low source impedance such that the voltage drop does not exceed the limits when the maximum current is flowing. The faster the current transients, the more challenging this gets. Adding decoupling capacitors to the PDN helps to provide a low impedance over a wide frequency range but also brings the risk of resonance peaks in the PDN. A simple PDN impedance measurement can help in verifying the PDN design. It will reveal critical resonances that could lead to system failures. This presentation will cover the basics of dynamic output impedance and PDN impedance, focusing on measuring low impedance using the Bode 500 in conjunction with Picotest PDN probes.