ISL6557A 데이터 시트보기 (PDF) - Renesas Electronics

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ISL6557A

Multiphase PWM Controller for CORE Voltage Regulation

Renesas Electronics 

ISL6557A

COMP

ERROR

AMPLIFIER

+

FB

-

-

+

+

-

DAC

&

REFERENCE

+

-

IOUT

VDIFF

+

x1

-

RGND

+

-

+

-

+

-

VSEN

PWM

CIRCUIT

PWM

CIRCUIT

PWM

CIRCUIT

AVERAGE

CURRENT

SENSE

CURRENT

SENSE

CURRENT

SENSE

PWM1

VIN

L1

ISEN1

RISEN1

PWM2

VIN

L2

ISEN2

RISEN2

PWM3

VIN

L3

ISEN3

RISEN3

FIGURE 1. SIMPLIFIED BLOCK DIAGRAM OF THE ISL6557A IN A 3-PHASE CONVERTER

VOUT

CO

P

LOAD

Operation

Multi-Phase Power Conversion

Multi-phase power conversion provides the most cost-effective

power solution when load currents are no longer easily

supported by single-phase converters. Although its greater

complexity presents additional technical challenges, the multi-

phase approach offers cost-saving advantages with improved

response time, superior ripple cancellation, and excellent

thermal distribution.

INTERLEAVING

The switching of each channel in a multi-phase converter is

timed to be symmetrically out of phase with each of the other

channels. In a 4-phase converter, each channel switches 1/4

cycle after the previous channel and 1/4 cycle before the

following channel. As a result, the four-phase converter has a

combined ripple frequency four times greater than the ripple

frequency of any one phase. In addition, the peak-to-peak

amplitude of the combined inductor currents is reduced in

proportion to the number of phases (Equations 1 and 2).

Increased ripple frequency and lower ripple amplitude mean

FN9068 Rev 3.00

July 2004

that the designer can use less per-channel inductance and

lower total output capacitance for any performance

specification.

IL1 + IL2 + IL3, 7A/DIV

IL3, 7A/DIV

PWM3, 5V/DIV

IL2, 7A/DIV

IL1, 7A/DIV

PWM2, 5V/DIV

PWM1, 5V/DIV

1s/DIV

FIGURE 2. PWM AND INDUCTOR-CURRENT WAVEFORMS

FOR 3-PHASE CONVERTER

Page 6 of 18

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