3PHASEPWM Datasheet, PDF (5/5 Pages) International Rectifier – 3-Phase Synchronous PWM Controller IC Provides an Integrated Solution for Intel VRM 9.0 Design Guidelines

Inductor Current
in each phase
rises
Figure 4 - Normalized output current across output
capacitor, as a function of duty cycle, (Peak to peak
current normalized to the Vo/(L3Fs) at zero duty
cycle).
It is shown that the output current ripple is
greatly reduced by multi-phase operation. At the
certain duty cycle D=1/N, where N is the phase
number, the output ripple will be near zero due
to complete cancellation of inductor current
ripple. The optimum number of phases exists for
different applications.
Built-in Synchronous-Rectifier Driver
Synchronous rectification reduces conduction
losses in the rectifier by shunting the normal
Schottky diode with a low on-resistance
MOSFET switch. The synchronous rectification
also ensures good transient dynamic. The 3-
phase synchronous rectifier MOSFET drivers
are built inside the IRU3055.
Transient Response
The IRU3055 delivers transient response that
meets Intel VRM 9.0 design guidelines with no
oscillation and a voltage drop <100mV for a
60A step load.
Drop <100mV
Figure 5 - 3-phase inductor current and Vout at 60A
dynamic load response
Conclusion
With the development of new microprocessors
always requiring more power, voltage are
dropping to reduce power dissipation, driving
currents upward exponentially. Higher currents
also lead to faster transient response
requirements and higher switching frequencies.
Multiphase topology is the preferred topology to
address the functionality of today’s
microprocessors voltage regulation requirements
in a compact footprint at an acceptable cost. 3-
phase converters appear to be the preferred way
of economically meeting the design guidelines
for Intel VRM9.0. The IRU3055 3-phase
synchronous PWM controller IC provides an
integrated solution for a straightforward
implementation of Intel VRM 9.0.
As next generation processors emerge with more
stringent power supply requirements and
additional functionality, new approaches and
advances in technology will be needed. More
phases might be needed to meet the ever-
increasing currents. With more phases come
more design complexity, power dissipation and
response delay. The partitioning of
functionalities within voltage regulators will
need to be optimized to provide the best
performance at the best cost in compact
footprints.
5