isl6307 Intersil Corporation, isl6307 Datasheet - Page 12

• Manufacturer Part Number: isl6307
• Description: 6-phase Pwm Controller With 8 Bit Vid Code Capable Of Precision Rds On Or Dcr Differential Current
• Manufacturer: Intersil Corporation

voltage developed across the lower MOSFET’s R
which is the channel current scaled by R
VR_RDY - VR_RDY is used as an indication of the end of
soft-start with certain delay per Intel VR11. It is an open-
drain logic output that is low impedance until the soft-start is
completed. It will be pulled low again once the undervoltage
point is reached.
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 over current 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 not used, keep this pin open.
IDROOP - The output pin of sensed average channel
current which is proportional 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 proportional to 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, ISL6307 will go into OCP mode, this means 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 5V. The voltage at this pin is proportional to VR
temperature. ISL6307 monitor the VR temperature based
the voltage at TM pin and output VR_HOT and VR_FAN
control signals.
VR_HOT - An indication output pin of high VR temperature.
It is an open-drain logic output with low impedance. It will be
12
DS(ON)
and R
DS(ON)
ISEN
,
.
ISL6307
pulled high when measured VR temperature reaches certain
level.
VR_FAN - An indication output pin of VR temperature high
warning with open-drain logic. It will be pulled high when
measured VR temperature reaches certain level. VR_FAN
will be pulled to high before VR_HOT.
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
ISL6307 controller helps reduce the complexity of
implementation by integrating vital functions and requiring
minimal output components. The block diagrams on pages
4, 5, 6 and 7 provide top level views of multiphase power
conversion using the ISL6307 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 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. PWM AND INDUCTOR-CURRENT WAVEFORMS
PWM1, 5V/DIV
IL1 + IL2 + IL3, 7A/DIV
FOR 3-PHASE CONVERTER
IL1, 7A/DIV
PWM3, 5V/DIV
1µs/DIV
IL3, 7A/DIV
PWM2, 5V/DIV
IL2, 7A/DIV
March 9, 2006
FN9224.0