By Benjamin Dannan and Steven Sandler, Picotest.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 multi-topology DC-DC regulators is a challenge for any design engineer...
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