EB212 Datasheet, PDF (1/8 Pages) Motorola, Inc – Using Data Sheet Impedances for RF LDMOS Devices

MOTOROLA
Freescale Semiconductor, Inc.
SEMICONDUCTOR ENGINEERING BULLETIN
Using Data Sheet Impedances
for RF LDMOS Devices
Prepared by: Darin Wagner
Motorola Semiconductor Products Sector
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INTRODUCTION
This document explains the format used by Motorola for
presenting LDMOS impedance information for both
single - ended and push - pull devices on RF Power data
sheets. The purpose of this document is to clarify the use of
this information in the initial design of input and output
matching networks for these devices.
Multiple methods are available for impedance extraction.
The scope of this document does not cover detailed extraction
methods; however, a possible extraction method is explained
here. Whichever method is used, the main concern to be
addressed is the need to de - embed the extracted data back
to the reference plane of the device as shown in Figure 1.
As a byproduct of the impedance extraction methodology,
a zero length width step simulation block should be used
during simulation The MSTEP block for Agilent Advanced
Design System (ADS) users shows the difference between
the reference plane width and the copper lead pad width.
Figure 2 illustrates that the copper lead pad width (Dimension
“b”) is larger than the reference plane width (Dimension “a”).
For more information on this topic, the reference provided
at the end of this document is a rigorous but accurate method
for impedance measurements:
DUT Reference Plane
ÎÎÎÎ
MRF
XXXXX
a
b
DUT
Reference Planes
DUT
Reference Planes
Figure 1. Location of Reference Planes on a Package
b
Figure 2. Illustration of the Instantaneous
Impedance Change and Need for MSTEP Blocks
REV 0
 Motorola, Inc. 2004
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