ISL6569A Datasheet, PDF (8/22 Pages) Intersil Corporation – Multi-Phase PWM Controller

ISL6569A
OFS
x0.1
100µA
COMP
+
-
REFERENCE
&
DAC
+
-
+
FB
-
ERROR
AMPLIFIER
IOUT
I_OUT
VDIFF
-
x1
+
VSEN
+
-
+
-
RGND
PWM
CIRCUIT
PWM
CIRCUIT
AVERAGE
CURRENT
SENSE
CURRENT
SENSE
PWM1
VIN
L₁
ISEN1
R_ISEN1
PWM2
V_OUT
µP
C_O
LOAD
VIN
L₂
ISEN2
R_ISEN2
FIGURE 1. SIMPLIFIED BLOCK DIAGRAM OF A ISL6569A CONVERTER
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
2.0µs, 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.
IL1 + IL2, 7A/DIV
IL2, 7A/DIV
PWM2, 5V/DIV
IL1, 7A/DIV
PWM1, 5V/DIV
1µs/DIV
FIGURE 2. PWM AND INDUCTOR-CURRENT WAVEFORMS
FOR 2-PHASE CONVERTER
8
FN9092.2
December 29, 2004