Device-Specific Power Delivery Network (PDN) Tool 2.0 User Guide
ID
683293
Date
8/24/2021
Public
1.2.2.1.1. Device Selection Section
1.2.2.1.2. Power Rail Data and Configuration Section
1.2.2.1.3. Meeting Target Impedance when Entering 0 A into the PDN Tool
1.2.2.1.4. Dealing with Multiple Shared Power Supply Pin Types
1.2.2.1.5. VRM Data Section
1.2.2.1.6. Rail Group Summary Section
1.2.2.1.7. VRM Impedance Section
1.2.2.1.8. BGA Via Section
1.2.2.1.9. Plane Section
1.2.2.1.10. Spreading Section
1.2.2.1.11. Implementing Split Planes
1.2.2.1.12. FEFFECTIVE Section
1.2.2.1.13. Decoupling Section
1.2.2.1.14. Results Summary Section
1.2.2.1.15. Recommended Flow for Deriving Decoupling for an FPGA System using the System_Decap Tab
1.2.4. Troubleshooting ZEFF
When the decoupling mode is set to Auto, this may result in a ZEFF value that is too high. This can happen when the PCB parameters you entered result in an inefficient PDN, and the current to be decoupled by the PCB are unrealistically high.
With difficult PCB and current parameters, auto decoupling continues to add decoupling capacitors until it determines they have little effect. This results in hundreds of capacitors. You can achieve decoupling schemes with similar performance manually using far fewer capacitors.