ISL6561CRZ Intersil, ISL6561CRZ Datasheet - Page 24

• Manufacturer Part Number: ISL6561CRZ
• Description: IC CTRLR PWM MULTIPHASE 40-QFN
• Manufacturer: Intersil

Specifications of ISL6561CRZ

• Applications: Controller, Intel VR10X
• Voltage - Input: 3 ~ 12 V
• Number Of Outputs: 4
• Voltage - Output: 0.84 ~ 1.6 V
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 40-VFQFN, 40-VFQFPN
• Input Voltage: 12V
• Output Voltage: 1.65V
• Supply Voltage Range: 4.75V To 5.25V
• Digital Ic Case Style: QFN
• No. Of Pins: 40
• Operating Temperature Range: 0°C To +70°C
• Filter Terminals: SMD
• Rohs Compliant: Yes
• Control Mode: Voltage
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

For a two phase design, use Figure 16 to determine the
input-capacitor RMS current requirement given the duty
cycle, maximum sustained output current (I
of the per phase peak-to-peak inductor current (I
Select a bulk capacitor with a ripple current rating which will
minimize the total number of input capacitors required to
support the RMS current calculated. The voltage rating of
the capacitors should also be at least 1.25 times greater
than the maximum input voltage.
Figures 17 and 18 provide the same input RMS current
information for three and four phase designs respectively.
Use the same approach to selecting the bulk capacitor type
and number as described above.
Low capacitance, high-frequency ceramic capacitors are
needed in addition to the bulk capacitors to suppress leading
and falling edge voltage spikes. The result from the high
current slew rates produced by the upper MOSFETs turn on
FIGURE 17. NORMALIZED INPUT-CAPACITOR RMS CURRENT
FIGURE 16. NORMALIZED INPUT-CAPACITOR RMS CURRENT
0.3
0.2
0.1
0.3
0.2
0.1
0
0
0
0
I
I
L,PP
L,PP
I
I
I
L,PP
L,PP
L,PP
= 0
= 0.25 I
vs DUTY CYCLE FOR 2-PHASE CONVERTER
VS DUTY CYCLE FOR 3-PHASE CONVERTER
= 0
= 0.5 I
= 0.75 I
0.2
0.2
O
O
O
DUTY CYCLE (V
DUTY CYCLE (V
0.4
0.4
24
I
I
L,PP
L,PP
= 0.5 I
= 0.75 I
0.6
0.6
O
O
/ V
/ V
IN
IN
O
)
)
O
O
), and the ratio
0.8
0.8
L,PP
) to I
1.0
1.0
O
.
ISL6561
and off. Select low ESL ceramic capacitors and place one as
close as possible to each upper MOSFET drain to minimize
board parasitic impedances and maximize suppression.
MULTI-PHASE RMS IMPROVEMENT
Figure 19 is provided as a reference to demonstrate the
dramatic reductions in input-capacitor RMS current upon the
implementation of the multi-phase topology. For example,
compare the input rms current requirements of a two-phase
converter versus that of a single phase. Assume both
converters have a duty cycle of 0.25, maximum sustained
output current of 40A, and a ratio of I
single phase converter would require 17.3 Arms current
capacity while the two-phase converter would only require
10.9 Arms. The advantages become even more pronounced
when output current is increased and additional phases are
added to keep the component cost down relative to the
single phase approach.
FIGURE 18. NORMALIZED INPUT-CAPACITOR RMS CURRENT
FIGURE 19. NORMALIZED INPUT-CAPACITOR RMS CURRENT
0.3
0.2
0.1
0.6
0.4
0.2
0
0
0
0
I
I
L,PP
L,PP
= 0
= 0.25 I
VS DUTY CYCLE FOR 4-PHASE CONVERTER
I
I
I
VS DUTY CYCLE FOR SINGLE-PHASE
CONVERTER
L,PP
L,PP
L,PP
0.2
0.2
= 0
= 0.5 I
= 0.75 I
O
DUTY CYCLE (V
DUTY CYCLE (V
O
O
0.4
0.4
I
I
L,PP
L,PP
= 0.5 I
= 0.75 I
0.6
0.6
O
O
C,PP
/ V
/ V
IN
IN
O
O
)
)
to I
O
0.8
0.8
of 0.5. The
May 12, 2005
FN9098.5
1.0
1.0