Setting up the pdn tool, Setting up the pdn tool -2, Figure 1–1 – Altera Power Delivery Network User Manual

Page 6: And the capacitor mounting inductance (l

1–2

Chapter 1: Power Delivery Network (PDN) Tool User Guide

Setting Up the PDN Tool

Power Delivery Network (PDN) Tool User Guide

Altera Corporation

Beyond lower frequencies, the VRM impedance is primarily inductive, making it
incapable of meeting the transient current requirement. The on-board discrete
decoupling capacitors must provide the required low impedance from low to high
frequencies, depending on the capacitor intrinsic parasitics (R

, C

, L

) and the

capacitor mounting inductance (L

mntN

). The interplanar capacitance between the

power-ground planes typically has lower inductance than the discrete decoupling
capacitor network, making it more effective at higher frequencies (tens of MHz). The
effectiveness of the decoupling capacitors is limited by the PCB spreading inductance
and the ball grid array (BGA) via inductance that a given capacitor encounters with
respect to the FPGA. To simplify the circuit topology, the PDN tool models the
distributed nature of PCB spreading, BGA inductance, and resistance with a single
lumped inductor and resistor.

Setting Up the PDN Tool

Figure 1–2

shows the various tabs of the PDN tool spreadsheet.

Table 1–1

describes the PDN tool tabs.

Figure 1–1. PDN Circuit Topology

Altera FPGA

Device

BGR Via

R and L

Spreading

R and L

Planar
R and C

LmntN

Lmnt3

Lmnt2

Lmnt1

LcN

CcN

RcN

Lc3

Cc3

Rc3

Lc2

Cc2

Rc2

Lc1

Cc1

Rc1

Decoupling
CAP Model

Lvrm

Rvrm

VRM

VRM Model

Figure 1–2. Tabs in the PDN Tool

Table 1–1. Description of Tabs in PDN Tool (Sheet 1 of 2)

Tab

Description

Release Notes

This tab provides the legal disclaimers, the revision history of the tool, and the user
agreement.

Introduction

This tab shows the schematic representation of the circuit that is modeled as part of the PDN
tool. The tab also provides a brief Quick Start instruction on using the tool.

Decap Selection

This tab provides an interface to input the various parameters and observe the resultant
impedance profile. This is the main user interface to the tool.