Device-Specific Power Delivery Network (PDN) Tool 2.0 User Guide

ID 683293
Date 8/24/2021
Public
Document Table of Contents

1.3.2.3. VRM Impedance

The PDN tool has default Library R and L models for VRM Impedance.

If a VRM model is available from the vendor, you can select the Custom option to replace the default values by directly overriding the new values.

Figure 27. VRM Impedance
Note: The single R and L assumption in the tool is for 1-phase single VRM. For multi-phase VRM usage, the simplest method for rough estimation is to divide the default numbers by the number of phases. For example, if the default values for a single switcher and four-phase VRM are R = 1 mΩ and L = 20 nH, then you can estimate the final values as R = 0.25 mΩ and L = 5 nH. Make note of how many phases of VRM you use in each PDN design. The tool may recommend bulk cap solutions that are significantly different.