I have just (20 mins ago) started looking at the possibility of using PMBus in future products and have come across the PowerOne licensing issue (referenced by electronicdesign.com), but also other info that says the bus is an open technology...

I am unclear as to who exactly needs to license to use this in a product.

E.g. if we wanted to produce a power supply that used PMBus enabled POL devices or PMBus controllers I'm guessing the device manufacturer needs to be the one licensed and not us, is that correct?

If we wanted to implement an MCU in our theoretical PSU, as an PMBus device/controller would we then need to license it?

Going back to the first case where only pre-licensed devices are used, if the bus master was a computer then the computer would require programming as a type of PMBus master controller - would that require licensing?

Has been suggested that the license is only on POL regulators, is that the case does anyone know?

  • 1
    \$\begingroup\$ Um, you need to make up your mind on protocols. Your question title cites PMBus but the body of the question is about SMBus. SMBus is not PMBus. SMBus is a closed standard that requires licensing. PMBus is an open standard. Also, AFAIK, Power-One's claim against PMBus hasn't yet been contested beyond that single lawsuit and appears to be limited to digitally-controlled DC/DC point-of-load converters. \$\endgroup\$ Jun 6 '13 at 13:57
  • \$\begingroup\$ Whoops, meant PMBus througout, will edit Q. Thanks \$\endgroup\$
    – Toby
    Jun 6 '13 at 14:20

The meat-and-potatoes of the licensing issue is as follows: (I am not a lawyer)

  • Power-One holds a patent that covers their Z-One point-of load converter: U.S. Patent No. 7,000,125
  • Power-One sued Artesyn over a point-of-load product that was never released to the marketplace, based around PMBus
  • Patent 7,000,125 was interpreted to cover the following:
    • A digital power control system for programming, controlling, and monitoring an array of Point of Load regulators using a data bus for communication with and control of the Point of Load regulators, where:
    • Point of Load Regulator is a dc-dc switching voltage regulator designed to receive power from a voltage bus on a printed circuit board, and adapted to power a portion of the devices on the board and to be placed near the one or more devices being powered as part of a distributed board-level power system.
  • Artesyn lost and had to pay $100 (one hundred dollars)
  • Power-One maintains that any POL converter with digital control and/or communication needs a license

Some quick searches show me that several companies have entered into licensing agreements with Power-One concerning digital power:


SO ... if you're using an off-the-shelf PMBus controller in a POL application, check that the manufacturer has a license. If you're spinning your own custom solution with a microcontroller, I suggest using a micro for which the manufacturer has a license.

That, and call a patent lawyer. Seriously. This patent business is exceedingly nasty.

  • \$\begingroup\$ Many thanks or clarifying that, thankfully my application does not concern POLs \$\endgroup\$
    – Toby
    Jun 6 '13 at 23:13
  • 1
    \$\begingroup\$ From what I've heard, non-POL applications don't bother with the license since the patent is completely untested beyond the scope of a POL. \$\endgroup\$ Jun 7 '13 at 11:33

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