ISL6569ACR datasheet(8/22 Pages) RENESAS

8 / 22 page

ISL6569A

FN9092 Rev 2.00

Page 8 of 22

Dec 29, 2004

Interleaving

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

timed to be symmetrically out of phase with the other

channel. In a 2-phase converter, channel-2 switches half a

cycle after channel-1. As a result, the converter has a ripple

frequency twice that of either phase. Figure 2 illustrates the

multiplicative effect on output ripple frequency. The two

channel currents (IL1 and IL2), combine to form the AC

ripple current and the DC load current. The ripple

component has twice the ripple frequency of either channel

current. Each PWM pulse is terminated half of a cycle, or

2.0

s, after the PWM pulse of the previous phase. The peak-

to-peak current waveform for each phase is about 7A, and

the dc components of the inductor currents combine to feed

the load.

RISEN1

ERROR

AMPLIFIER

ISEN1

VOUT

PWM1

FIGURE 1. SIMPLIFIED BLOCK DIAGRAM OF A ISL6569A CONVERTER

IOUT

P

LOAD

x 1

RGND

VSEN

VDIFF

DAC

REFERENCE

COMP

VIN

RISEN2

ISEN2

PWM2

VIN

CURRENT

SENSE

AVERAGE

CURRENT

SENSE

PWM

CIRCUIT

PWM

CIRCUIT

x0.1

100

A

IOUT

OFS

FIGURE 2. PWM AND INDUCTOR-CURRENT WAVEFORMS

FOR 2-PHASE CONVERTER

s/DIV

PWM2, 5V/DIV

PWM1, 5V/DIV

IL2, 7A/DIV

IL1, 7A/DIV

IL1 + IL2, 7A/DIV

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