May 18, 2021
"High speed printed circuit board (PCB) design requires well designed power delivery networks (PDN) to support today's FPGAs or custom mixed-signal ASICs. The PDN contains important impedance information that can offer the designer insight into how a system will react to dynamic currents. The PDN is the transmission line connecting the voltage regulator module (VRM) and the load, making the VRM a good starting point for a successful PDN design.
Vendor information for a VRM’s output impedance is not always provided, and when it is provided it may not be accurate. Further, measuring ultra-low impedance on multiple VRMs, or a multi-topology DC-DC regulator, is a challenge for many design engineers. The 2-port shunt-through measurement is the gold standard for measuring a VRM’s output impedance in the milliOhm and sub-milliOhm region ; however, it is not always possible to make these measurements without including dedicated RF connectors on the PCB or device under test (DUT). Therefore, when a designer makes these types of measurements with a vector network analyzer (VNA), the method of connecting the DUT requires attention to detail to ensure inductance is minimized to allow an accurate measurement..."
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