IEEE Power Electronics Magazine - September 2014 - 39

One interesting feature of
AVSBus is the ability of the
Power
Processor/
master to send a command to
Management IC
FPGA/ASIC
the slave with the instruction
Interleaved
PWM1
to hold the command rather
Buck
than executing it immediately.
Power Stage
VOut1
Suppose that a master is comRail 1
municating with a power supController
Interleaved
ply controller that controls
PWM2
Buck
three output voltages used by
Power Stage
the master. The master can
AVSBus
AVSBus
send a command for the first
Master
voltage with the instruction to
hold, send another command
VOut2
PWM3
Rail 2
Buck
for the second voltage with the
Controller
Power Stage
instruction to hold, and then
send a command to the third
voltage with the instruction
VOut3
PWM4
Buck
Rail 3
to "commit." When the power
Power Stage
Controller
supply controller receives the
command with the instruction to commit, it executes
all three commands simulta- fig 4 The AVSBus with multiple power supply rails.
neously. This example is important when the logic device
voltages are being changed and restrictions on voltage differthe commercial power supply industry. From Revision 1.0,
ences between each supply voltage must be observed.
PMBus has grown and evolved into the de facto standard
The AVSBus is an important new tool the system enfor digital power management. With the recent release of
gineer and logic designer can use to reduce energy conRevision 1.3 and new energy-saving AVSBus interface,
sumption. It is a full digital power management protocol
PMBus has taken an important step that offers system manwith a well-defined electrical interface, data transmisufacturers a new tool for reducing energy consumption.
sion format and flow control, and a very compact and
elegant command language. The feedback to the PMBus
About the Author
working group from the system manufacturers has been
Robert V. White (bob.white@ieee.org) received a B.S.E.E.
very positive, and several semiconductor manufacturers
degree from the Massachusetts Institute of Technology, an
are working on implementing AVSBus in their power supM.S.E.E. degree from Worcester Polytechnic Institute, and
ply controllers.
is currently pursuing a Ph.D. degree in power electronics at
the University of Colorado, Boulder. He has over 30 years of
experience in power electronics. He has held managerial
Summary
and individual contributor positions in product developThis article has described the origins and basic operations
ment, technology development, applications and systems
of the PMBus, the result of the first open standard effort in
engineering, and technical marketing. He is considered the
father of the PMBus and an expert in digital power. He is
To Learn More
also working with the application of wide-bandgap and
compound semiconductors in switching applications. He is
This article provided only an introductory description of the
currently the president and chief engineer of Embedded
PMBus and AVSBus. If you would like to learn more, please visit
Power Labs, a power electronics consulting company. He
the PMBus Web site at www.PMBus.org. From that page, you can
has been very active in the IEEE Power Electronics Socirequest that the PMBus specifications be sent to you at no cost.
ety and the IEEE Applied Power Electronics Conference
Under the "News" tab, there are a number of blog entries that
and Exposition (APEC) committees, including twice servdiscuss Revision 1.3 and, in particular, provide several discussions
ing as the APEC general chair. He was awarded the IEEE
of the new AVSBus.
Millennium Medal in 2000 and the IEEE Power Electronics
The SMIF also provides technical support for the SMBus and
Society Distinguished Service Award in 2002. He is a FelPMBus specifications. You can send your questions about the
low of the IEEE.
specifications and implementation issues to techquestions@
smiforum.org.

September 2014

z IEEE PowEr ElEctronIcs MagazInE

http://www.PMBus.org

Table of Contents for the Digital Edition of IEEE Power Electronics Magazine - September 2014