ISL6561CRZ Intersil, ISL6561CRZ Datasheet - Page 11

• 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

OVP - Overvoltage protection pin. This pin pulls to VCC and
is latched when an overvoltage condition is detected.
Connect this pin to the gate of an SCR or MOSFET tied from
V
pin may be pulled above VCC as high as 15V to ground with
an external resistor. However, it is only capable of pulling low
when VCC is above 2V.
IDROOP - IDROOP is the ouput pin of sensed average
channel current which is propotional to load current. In the
application which does not require loadline, leave this pin
open. In the application which requires load line, connect this
pin to FB so that the sensed average current will flow
through the resistor between FB and VDIFF to create a
voltage drop which is propotional to load current.
Operation
Multi-Phase Power Conversion
Microprocessor load current profiles have changed to the
point that the advantages of multi-phase power conversion
are impossible to ignore. The technical challenges
associated with producing a single-phase converter which is
both cost-effective and thermally viable have forced a
change to the cost-saving approach of multi-phase. The
ISL6561 controller helps simplifying the implementation by
integrating vital functions and requiring minimal output
components. The block diagrams on pages 2 and 3 provide
top level views of multi-phase power conversion using the
ISL65556ACB and ISL6561CR controllers.
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 3-phase converter, each channel switches 1/3
cycle after the previous channel and 1/3 cycle before the
following channel. As a result, the three-phase converter has
a combined ripple frequency three times greater than the
IN
FIGURE 1. PWM AND INDUCTOR-CURRENT WAVEFORMS
or V
OUT
PWM1, 5V/DIV
IL1 + IL2 + IL3, 7A/DIV
to ground to prevent damage to the load. This
FOR 3-PHASE CONVERTER
IL1, 7A/DIV
PWM3, 5V/DIV
11
1µs/DIV
IL3, 7A/DIV
PWM2, 5V/DIV
IL2, 7A/DIV
ISL6561
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
that the designer can use less per-channel inductance and
lower total output capacitance for any performance
specification.
Figure 1 illustrates the multiplicative effect on output ripple
frequency. The three channel currents (IL1, IL2, and IL3)
combine to form the AC ripple current and the DC load
current. The ripple component has three times the ripple
frequency of each individual channel current. Each PWM
pulse is terminated 1/3 of a cycle after the PWM pulse of the
previous phase. The peak-to-peak current for each phase is
about 7A, and the dc components of the inductor currents
combine to feed the load.
To understand the reduction of ripple current amplitude in
the multi-phase circuit, examine the equation representing
an individual channel’s peak-to-peak inductor current.
In Equation 1, V
voltages respectively, L is the single-channel inductor value,
and f
The output capacitors conduct the ripple component of the
inductor current. In the case of multi-phase converters, the
capacitor current is the sum of the ripple currents from each
of the individual channels. Compare Equation 1 to the
expression for the peak-to-peak current after the summation
of N symmetrically phase-shifted inductor currents in
Equation 2. Peak-to-peak ripple current decreases by an
amount proportional to the number of channels. Output-
voltage ripple is a function of capacitance, capacitor
equivalent series resistance (ESR), and inductor ripple
I
PP
FIGURE 2. CHANNEL INPUT CURRENTS AND INPUT-
=
S
(
----------------------------------------------------- -
V
is the switching frequency.
IN
INPUT-CAPACITOR CURRENT, 10A/DIV
–
L f
V
CAPACITOR RMS CURRENT FOR 3-PHASE
CONVERTER
OUT
S
CHANNEL 1
INPUT CURRENT
10A/DIV
V
IN
IN
) V
and V
OUT
CHANNEL 2
INPUT CURRENT
10A/DIV
OUT
CHANNEL 3
INPUT CURRENT
10A/DIV
1µs/DIV
are the input and output
May 12, 2005
FN9098.5
(EQ. 1)