ISL6327 Intersil Corporation, ISL6327 Datasheet - Page 10

• Manufacturer Part Number: ISL6327
• Description: Enhanced 6-Phase PWM Controller
• Manufacturer: Intersil Corporation

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VR_RDY - VR_RDY indicates that the soft-start is completed
and the output voltage is within the regulated range around
VID setting. It is an open-drain logic output. When OCP or
OVP occurs, VR_RDY will be pulled to low. It will also be
pulled low if the output voltage is below the undervoltage
threshold.
OFS - The OFS pin provides a means to program a DC
offset current for generating a DC offset voltage at the REF
input. The offset current is generated via an external resistor
and precision internal voltage references. The polarity of the
offset is selected by connecting the resistor to GND or VCC.
For no offset, the OFS pin should be left unterminated.
TCOMP - Temperature compensation scaling input. The
voltage sensed on the TM pin is utilized as the temperature
input to adjust ldroop and the overcurrent protection limit to
effectively compensate for the temperature coefficient of the
current sense element. To implement the integrated
temperature compensation, a resistor divider circuit is
needed with one resistor being connected from TCOMP to
VCC of the controller and another resistor being connected
from TCOMP to GND. Changing the ratio of the resistor
values will set the gain of the integrated thermal
compensation. When integrated temperature compensation
function is not used, connect TCOMP to GND.
OVP - The Overvoltage protection output indication pin. This
pin can be pulled to VCC and is latched when an overvoltage
condition is detected. When the OVP indication is not used,
keep this pin open.
IDROOP - IDROOP is the output pin of the sensed average
channel current which is proportional to the 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 proportional to the load current.
IOUT - IOUT has the same output as IDROOP with
additional OCP adjustment function. In actual application, a
resistor needs to be placed between IOUT and GND to
ensure the proper operation. The voltage at IOUT pin will be
proportional to the load current. If the voltage is higher than
2V, ISL6327 will go into the OCP mode, this means it will
shut down first and then hiccup. The additional OCP trip
level can be adjusted by changing the resistor value.
TM - TM is an input pin for VR temperature measurement.
Connect this pin through NTC thermistor to GND and a
resistor to Vcc of the controller. The voltage at this pin is
reverse proportional to the VR temperature. ISL6327
monitors the VR temperature based on the voltage at the TM
pin and the output signals at VR_HOT and VR_FAN.
VR_HOT - VR_HOT is used as an indication of high VR
temperature. It is an open-drain logic output. It will be open
when the measured VR temperature reaches a certain level.
10
ISL6327
VR_FAN - VR_FAN is an output pin with open-drain logic
output. It will be open when the measured VR temperature
reaches a certain level.
Operation
Multiphase Power Conversion
Microprocessor load current profiles have changed to the
point that the advantages of multiphase 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 multiphase. The
ISL6327 controller helps reduce the complexity of
implementation by integrating vital functions and requiring
minimal output components. The block diagrams on pages
3, 4, and 5 provide top level views of multiphase power
conversion using the ISL6327 controller.
Interleaving
The switching of each channel in a multiphase 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
ripple frequency of any one phase. In addition, the peak-to-
peak amplitude of the combined inductor current is reduced
in proportion to the number of phases (Equations 1 and 2).
The increased ripple frequency and the 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 triggered 1/3 of a cycle after the start of the PWM
June 5, 2006
FN9276.1