By Benjamin Dannan and Steven Sandler, Picotest.com, and Subbaiah M. Pemmaiah, Coppermountaintech.com
High speed Printed Circuit Board (PCB) design requires well designed Power Delivery Networks (PDN) to support today’s FPGAs and custom mixed-signal ASICs. The PDN contains important impedance information that can tell a designer how a system will react to dynamic currents and the impact of PCB layout. If we consider the PDN as a transmission line between the Voltage Regulator Module (VRM) and the load (ASICs), then a starting point for a good PDN design is the VRM.
Today VRMs need to supply power to multiple VDD cores to support FPGAs and/or custom ASICs using multi-gigabit Ethernet, PCIe, and DDR memory interfaces. With that being said, vendor information for a VRM’s output impedance is not available and not always accurate when it is supplied. Further, measuring ultra-low impedance on multiple VRMs or multitopology DC-DC regulators is a challenge for any design engineer...
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