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FN6802.2

August 31, 2010

Component Placement

Within the allotted implementation area, orient the switching

components first. The switching components are the most

critical because they carry large amounts of energy and tend

to generate high levels of noise. Switching component

placement should take into account power dissipation. Align

the output inductors and MOSFETs such that space between

the components is minimized while creating the PHASE

plane. Place the Intersil MOSFET driver IC as close as

possible to the MOSFETs they control to reduce the parasitic

impedances due to trace length between critical driver input

and output signals. If possible, duplicate the same placement

of these components for each phase.

Next, place the input and output capacitors. Position one high

frequency ceramic input capacitor next to each upper

MOSFET drain. Place the bulk input capacitors as close to the

upper MOSFET drains, as dictated by the component size

and dimensions. Long distances between input capacitors

and MOSFET drains result in too much trace inductance and

a reduction in capacitor performance. Locate the output

capacitors between the inductors and the load, while keeping

them in close proximity to the microprocessor socket.

Voltage-Regulator (VR) Design Materials

The tolerance band calculation (TOB) worksheets for VR

output regulation and IMON have been developed using the

Root-Sum-Squared (RSS) method with 3 sigma distribution

point of the related components and parameters. Note that

the “Electrical Specifications” table beginning on page 6

specifies no less than 6 sigma distribution point, not suitable

for RSS TOB calculation. Intersil also developed a set of

worksheets to support VR design and layout. Contact

Intersil’s local office or field support for the latest available

information.

ISL6334D