ISL6566AIR-T View Datasheet(PDF) - Intersil

Part Name

Description

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ISL6566AIR-T

Three-Phase Buck PWM Controller with Two Integrated MOSFET Drivers and One External Driver Signal

Intersil 

ISL6566A

to smooth the voltage transition during Dynamic VID

operations.

OFS

The OFS pin provides a means to program a dc current for

generating an offset voltage across the resistor between FB

and VDIFF. 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 unconnected.

OCSET

This is the overcurrent set pin. Placing a resistor from OCSET

to ICOMP allows a 100µA current to flow out this pin,

producing a voltage reference. Internal circuitry compares the

voltage at OCSET to the voltage at ISUM, and if ISUM ever

exceeds OCSET, the overcurrent protection activates.

ISEN1, ISEN2 and ISEN3

These pins are used for balancing the channel currents by

sensing the current through each channel’s lower MOSFET

when it is conducting. Connect a resistor between the

ISEN1, ISEN2, and ISEN3 pins and their respective phase

node. This resistor sets a current proportional to the current

in the lower MOSFET during its conduction interval.

UGATE1 and UGATE2

Connect these pins to the corresponding upper MOSFET

gates. These pins are used to control the upper MOSFETs

and are monitored for shoot-through prevention purposes.

Maximum individual channel duty cycle is limited to 66%.

BOOT1 and BOOT2

These pins provide the bias voltage for the corresponding

upper MOSFET drives. Connect these pins to appropriately-

chosen external bootstrap capacitors. Internal bootstrap

diodes connected to the PVCC pins provide the necessary

bootstrap charge.

PHASE1 and PHASE2

Connect these pins to the sources of the upper MOSFETs.

These pins are the return path for the upper MOSFET

drives.

LGATE1 and LGATE2

These pins are used to control the lower MOSFETs. Connect

these pins to the corresponding lower MOSFETs’ gates.

PWM3

Pulse-width modulation output. Connect this pin to the PWM

input pin of an Intersil driver IC if 3-phase operation is

desired.

EN_PH3

This pin has two functions. First, a resistor divider connected

to this pin will provide a POR power up synch between the

on-chip and external driver. The resistor divider should be

designed so that when the POR-trip point of the external

driver is reached the voltage on this pin should be 1.220V.

The second function of this pin is disabling PWM3 for 2-

phase operation. This can be accomplished by connecting

this pin to a +5V supply.

PGOOD

During normal operation PGOOD indicates whether the

output voltage is within specified overvoltage and

undervoltage limits. If the output voltage exceeds these limits

or a reset event occurs (such as an overcurrent event),

PGOOD is pulled low. PGOOD is always low prior to the end

of soft-start.

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 that is

both cost-effective and thermally viable have forced a

change to the cost-saving approach of multi-phase. The

ISL6566A controller helps simplify implementation by

integrating vital functions and requiring minimal external

components. The block diagram on page 2 provides a top

level view of multi-phase power conversion using the

ISL6566A 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 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

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).

8

FN9200.2

July 27, 2005

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