3PHASEPWM datasheet(5/5 Pages) IRF

5 / 5 page

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

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.

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

faster

transient

response

requirements and higher switching frequencies.

Multiphase topology is the preferred topology to

address

the

functionality

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

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

functionalities within voltage regulators will

need to be optimized to provide the best

performance at the best cost in compact

footprints.

Drop <100mV

Inductor Current

in each phase

rises

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