IR3084MPBF datasheet(7/45 Pages) IRF

7 / 45 page

IR3084

Page 7 of 45

07/20/2005

SYSTEM THEORY OF OPERATION

XPhase

TM Architecture

The XPhase

architecture is designed for multiphase interleaved buck converters which are used in

applications requiring small size, design flexibility, low voltage, high current and fast transient response. The

architecture can be used in any multiphase converter ranging from 1 to 16 or more phases where flexibility

facilitates the design trade−off of multiphase converters. The scalable architecture can be applied to other

applications which require high current or multiple output voltages.

As shown in Figure 2, the XPhase

TM architecture consists of a Control IC and a scalable array of phase

converters each using a single Phase IC. The Control IC communicates with the Phase ICs through a 5−wire

analog bus, i.e. bias voltage, phase timing, average current, error amplifier output, and VID voltage. The Control

IC incorporates all the system functions, i.e. VID, PWM ramp oscillator, error amplifier, bias voltage, and fault

protections etc. The Phase IC implements the functions required by the converter of each phase, i.e. the gate

drivers, PWM comparator and latch, over−voltage protection, and current sensing and sharing.

There is no unused or redundant silicon with the XPhase

TM architecture compared to others such as a 4 phase

controller that can be configured for 2, 3, or 4 phase operation. PCB Layout is easier since the 5 wire bus

eliminates the need for point−to−point wiring between the Control IC and each Phase. The critical gate drive and

current sense connections are short and local to the Phase ICs. This improves the PCB layout by lowering the

parasitic inductance of the gate drive circuits and reducing the noise of the current sense signal.

VR FAN

VID3

ADDITIONAL PHASES

INPUT/OUTPUT

CONTROL BUS

COUT

>> VID VOLTAGE

VID0

VID1

VID2

VOUT SENSE+

VR HOT

VR READY

IR3084

CONTROL

>> PWM CONTROL

>> PHASE TIMING

>> BIAS VOLTAGE

<< CURRENT SENSE

RCS

CCS

CIN

RCS

CCS

VID6

VID5

VIDSEL

VID7

VID4

VOUT-

VOUT SENSE-

12V

VOUT+

ENABLE

IR3086

PHASE

PHASE FAULT

IR3086

PHASE

CURRENT SHARE

PHASE FAULT

Figure 2 – System Block Diagram

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