ISL6327 Intersil Corporation, ISL6327 Datasheet - Page 9

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

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Functional Pin Description
VCC - Supplies the power necessary to operate the chip.
The controller starts to operate when the voltage on this pin
exceeds the rising POR threshold and shuts down when the
voltage on this pin drops below the falling POR threshold.
Connect this pin directly to a +5V supply.
GND - Bias and reference ground for the IC. The bottom
metal base of ISL6327 is the GND.
EN_PWR - This pin is a threshold-sensitive enable input for
the controller. Connecting the 12V supply to EN_PWR
through an appropriate resistor divider provides a means to
synchronize power-up of the controller and the MOSFET
driver ICs. When EN_PWR is driven above 0.875V, the
ISL6327 is active depending on status of EN_VTT, the
internal POR, and pending fault states. Driving EN_PWR
below 0.745V will clear all fault states and prime the ISL6327
to soft-start when re-enabled.
EN_VTT - This pin is another threshold-sensitive enable
input for the controller. It’s typically connected to VTT output
of VTT voltage regulator in the computer mother board.
When EN_VTT is driven above 0.875V, the ISL6327 is active
depending on status of ENLL, the internal POR, and pending
fault states. Driving EN_VTT below 0.745V will clear all fault
states and prime the ISL6327 to soft-start when re-enabled.
FS - Use this pin to set up the desired switching frequency. A
resistor, placed from FS to ground will set the switching
frequency. The relationship between the value of the resistor
and the switching frequency will be described by an
approximate equation.
SS - Use this pin to set up the desired start-up oscillator
frequency. A resistor, placed from SS to ground will set up
the soft-start ramp rate. The relationship between the value
of the resistor and the soft-start ramp up time will be
described by an approximate equation.
VID7, VID6, VID5, VID4, VID3, VID2, VID1 and VID0 -
These are the inputs to the internal DAC that generates the
reference voltage for output regulation. Connect these pins
either to open-drain outputs with or without external pull-up
resistors or to active-pull-up outputs. All VID pins have 40uA
internal pull-up current sources that diminish to zero as the
voltage rises above the logic-high level. These inputs can be
pulled up externally as high as VCC plus 0.3V.
VRSEL - VRSEL is the pin used to select the internal VID
code. When it is connected to GND, the extended VR10
code is selected. VRSEL pin has 40µA internal pull-up
current sources that diminish to zero as the voltage rises
above the logic-high level. When it’s floated or pulled to high,
VR11 code is selected. This input can be pulled up as high
as VCC plus 0.3V.
VDIFF, VSEN, and RGND - VSEN and RGND form the
precision differential remote-sense amplifier. This amplifier
9
ISL6327
converts the differential voltage of the remote output to a
single-ended voltage referenced to local ground. VDIFF is
the amplifier’s output and the input to the regulation and
protection circuitry. Connect VSEN and RGND to the sense
pins of the remote load. VDIFF is connected to FB through a
resistor.
FB and COMP - The inverting input and the output of the
error amplifier respectively. FB can be connected to VDIFF
through a resistor. A properly chosen resistor between
VDIFF and FB can set the load line (droop), when IDROOP
pin is tied to FB pin. The droop scale factor is set by the ratio
of the ISEN resistors and the inductor DCR or the dedicated
current sense resistor. COMP is tied back to FB through an
external R-C network to compensate the regulator.
DAC and REF - The DAC pin is the output of the precision
internal DAC reference. The REF pin is the positive input of
the Error Amp. In typical applications, a 1kΩ, 1% resistor is
used between DAC and REF to generate a precision offset
voltage. This voltage is proportional to the offset current
determined by the offset resistor from OFS to ground or
VCC. A capacitor is used between REF and ground to
smooth the voltage transition during Dynamic VID™
operations.
PWM1, PWM2, PWM3, PWM4, PWM5, PWM6 - Pulse
width modulation outputs. Connect these pins to the PWM
input pins of the Intersil driver IC. The number of active
channels is determined by the state of PWM3, PWM4,
PWM5, and PWM6. For 2-phase operation, connect PWM3
to VCC; similarly, PWM4 for 3-phase, PWM5 for 4-phase,
and PWM6 for 5-phase operation.
ISEN1+, ISEN1-; ISEN2+, ISEN2-; ISEN3+, ISEN3-;
ISEN4+, ISEN4-; ISEN5+, ISEN5-; ISEN6+, ISEN6- - The
ISEN+ and ISEN- pins are current sense inputs to individual
differential amplifiers. The sensed current is used for
channel current balancing, overcurrent protection, and droop
regulation. Inactive channels should have their respective
current sense inputs left open (for example, open ISEN6+
and ISEN6- for 5-phase operation).
For DCR sensing, connect each ISEN- pin to the node
between the RC sense elements. Tie the ISEN+ pin to the
other end of the sense capacitor through a resistor, R
The voltage across the sense capacitor is proportional to the
inductor current. Therefore, the sense current is proportional
to the inductor current, and scaled by the DCR of the
inductor and R
CONFIGURATION
6-Phase
5-Phase
4-Phase
3-Phase
TABLE 1. PHASE FIRING SEQUENCE
ISEN
.
PHASE SEQUENCE
1 - 2 - 3 - 4 - 5 - 6
1 - 2 - 3 - 4 - 5
1 - 2 - 4 - 3
1 - 2 - 3
June 5, 2006
ISEN
FN9276.1
.