ISL6307A Datasheet, PDF (12/33 Pages) Intersil Corporation – Ultra-high bandwidth 6-Phase PWM Controller with 8 Bit VID Code Capable of Precision RDS(ON) or DCR Differential Current Sensing

ISL6307A
voltage developed across the lower MOSFET’s R_DS(ON),
which is the channel current scaled by R_DS(ON) and R_ISEN.
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 input pin provides 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 as shown in the typical application diagrams.
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 load-line, 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, ISL6307A will go into OCP mode. The OCP trip level can
be adjusted by changing the resistor value.
DRVEN - Driver enable output pin. This pin can be used to
enable the MOSFET drivers which have enable pins such as
ISL6609, ISL6608 or other DrMOS devices. If ISL6307A is
used with Intersil’s ISL6612 drivers, it’s not necessary to use
this pin.
TM - TM is an input pin for VR temperature measurement.
Connect this pin through a NTC thermistor to GND and a
resistor to 5V. The voltage at this pin is proportional to the
VR temperature. ISL6307A monitors the VR temperature
based on the voltage at TM and triggers VR_FAN and
VR_HOT signals based on the temperature thresholds.
VR_HOT - An indication output pin of high VR temperature.
It is an open-drain logic output with low impedance. It will be
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 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
ISL6307A 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 ISL6307A controller.
IL1 + IL2 + IL3, 7A/DIV
IL3, 7A/DIV
PWM3, 5V/DIV
IL2, 7A/DIV
IL1, 7A/DIV
PWM2, 5V/DIV
PWM1, 5V/DIV
1µs/DIV
FIGURE 1. PWM AND INDUCTOR-CURRENT WAVEFORMS
FOR 3-PHASE CONVERTER
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).
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.
12
FN9236.0
February 6, 2006