ISL6569 Intersil Corporation, ISL6569 Datasheet - Page 8

• Manufacturer Part Number: ISL6569
• Description: Multi-Phase PWM Controller
• Manufacturer: Intersil Corporation

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 (IL1and 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 2.0µs, 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.
IOUT
VDIFF
FB
COMP
I
OUT
REFERENCE
100µA
x0.1
x 1
+
+
-
DAC
OFS
&
+
-
VSEN
AMPLIFIER
ERROR
8
FIGURE 1. SIMPLIFIED BLOCK DIAGRAM OF A ISL6569 CONVERTER
RGND
+
+
+
+
-
-
-
-
AVERAGE
CURRENT
CURRENT
ISL6569
CIRCUIT
CIRCUIT
SENSE
SENSE
PWM
PWM
In addition, the peak-to-peak amplitude of the combined
inductor currents is reduced in proportion to the number of
phases. To understand the reduction of ripple current
amplitude in the multi-phase circuit, examine the equation
FIGURE 2. PWM AND INDUCTOR-CURRENT WAVEFORMS
PWM1
PWM2
PWM1, 5V/DIV
ISEN1
ISEN2
FOR 2-PHASE CONVERTER
IL1 + IL2, 7A/DIV
R
R
IL1, 7A/DIV
ISEN1
ISEN2
VIN
VIN
1µs/DIV
L
L
1
2
C
PWM2, 5V/DIV
O
IL2, 7A/DIV
LOAD
V
µP
OUT