The verdict is in on the digital power-control patent
lawsuit between Power-One and Artesyn Technologies,
and it doesn’t bode well for the PMBus. Maybe
Power-One should change its name to “Power-
Won” now that a Texas jury has upheld the validity of its ZOne
digital power-management and power-control patents.
The jury found the patents to be valid and specifically ruled
that Artesyn Technologies infringed on one of the Power-
One patents. Artesyn is part of Emerson Electric’s Network
Power business unit.
Power-One believes its digital power-management and
power-control intellectual property (IP) applies to a range
of digital power-control products, systems, communications
methods, bus architectures, and implementations. This covers
dc-dc point-of-load (POL) implementations using data
bus communication, including the PMBus protocols.
Validation of the Power-One patents could put a dent
in the future of the PMBus. Power-One CEO Bill Yeates
says that if dc-dc POL PMBus users have printed-circuit
cards that have multiple POLs and a communication bus,
the technology will require a license from Power-One. No
license fee has been announced.
It’s not clear if the semiconductor manufacturers that
have ICs intended for PMBus applications are subject to
licensing their products. It would appear that they would be
exempt because they produce components that could only
be a part of a PMBus system.
But if their ICs are found in power supplies or customers’
system printed-circuit boards that infringe the Power-One
patents, they may stand a chance of being sued. Because of
this patent situation, it is likely that the market
for their ICs would certainly be reduced, at
least in the near term. Several companies
already have introduced PMBus ICs.
PMBus on the Market
Zilker Labs’ 3-A,
PMBus-compliant ZL2105 combines a synchronous
step-down dc-dc converter with integrated
synchronous power MOSFETs and key powermanagement
functions in a 6- by 6-mm package.
The IC is fully configurable with simple
pin-strap connections or resistor selection or
via the device’s on-board serial port using the
industry-standard PMBus command set. It
also provides the configurability, control, and
monitoring capabilities of digital power technology
without compromising efficiency.
Intersil’s ISL8601 is a single-phase pulsewidth
modulation (PWM) controller with
integrated MOSFET drivers utilizing analog
voltage mode control. Its extensive PMBus compliance enables
flexible power-supply design and comprehensive product
evaluation and testing. Besides the I2C interface, select
PMBus commands for the ISL8601 can also be programmed
via external resistors, bringing the power and flexibility of
PMBus into low-cost power-supply systems.
The LTC7510 from Linear Technology is a digital dc-dc
controller with onboard nonvolatile memory and a PMBus
interface for real-time reporting and controlling of POL
power-management attributes such as current, voltage,
and operating frequency and temperature. Power-supply
sequencing, margining, and turn-on/off are easily programmed
via the PMBus interface. The LTC7510 also provides
extensive POL fault-detection reporting capability.
Maxim’s MAX8688 integrated digital power-supply
controller and monitor IC can work with any existing POL
power supply to provide complete digital programmability.
It operates using a PMBus-compliant communication protocol
and can be programmed using this protocol or simply
with the use of a free GUI available from the Maxim Web
site that significantly reduces development time. Once the
configuration is complete, the results can be saved into EEPROM
or loaded onto the part through PMBus at power-up.
Primarion’s PX75xx family incorporates an industry-standard
PMBus serial interface for controlling and monitoring.
Digital PMBus-compliant POL power ICs are designed for
use in synchronous buck converters. Applications include
low-voltage distributed power supplies required to power
ASICs, FPGAs, DSPs, and memory for telecom, datacom,
server, and storage equipment.
The PX75xx family includes the
PX7510 single-phase digital integrated
power conversion and management
IC; the PX7520 dual-phase digital
integrated power conversion and management
IC; the PX7522 digital dualoutput/
dual-phase integrated power
management and conversion IC; and
the PX7542 dual-output, multiphase
digital dc-dc controller.
The UCD9112 from Texas Instruments
is a dual-phase synchronous
buck digital PWM (DPWM) controller
designed for POL power applications.
It integrates dedicated circuitry for dcdc
loop management with a microcontroller
core, flash memory, and PMBus
interface to support configurability,
monitoring, and POL management.
The UCD9112 can operate at switching
frequencies of up to 1 MHz. The
UCD7230 synchronous buck driver
works with the UCD9112. Besides its
4-A output drive capability, the driver
integrates current-limit, short-circuit
protection as well as undervoltage lockout
protection. The UCD7230’s 3.3-V,
10-mA linear regulator provides the
supply current for the controller.
The infringing power supply referred
to in the lawsuit was Artesyn’s DPL20C,
which is now said to be “in development”
and “coming soon” on the Artesyn
Web site. The DPL20C was the first
PMBus-compliant dc-dc converter to be
announced in September 2005.
Rated as a 20-A output, non-isolated
POL dc-dc converter, it featured an
extensive set of digital configuration,
monitoring, and diagnostic facilities accessible
via the PMBus interface. It also
boasted a 4.5- to 13.8-V input, 0.6- to
5.5-V programmable output, 20-A output
with 91% typical efficiency (12-V
input), and differential remote sense.
Protection features included overcurrent
and overvoltage.
Z-One vs. PMBus
Digital power
management provided by Z-One and
PMBus lets designers set a power supply’s
operating parameters, monitor
its operation, and perform corrective
measures in response to faults or
warnings. The ability to set a power
supply’s output voltage allows the same
hardware to provide different output
voltages by merely reprogramming.
Plus, the ability to monitor and maintain
a power-management subsystem
enhances its reliability and availability.
The Z-One digital system and PMBus
differ in how they partition powermanagement
tasks (see the figure). Z-One
products split the power-management
responsibilities between a firmwareenabled
digital power manager and
a POL-based DPWM IC. The PMBus
requires the designer to program the
computer according to the PMBus
protocol with much of the intelligence
residing in a system controller.
Also, the Z-One system operates only
with dc-dc converters, whereas the
PMBus can operate with dc-dc and
ac-dc converters. It should be noted
that the PMBus is just a protocol, not
the actual hardware.