IR3086

Page 6 of 15

9/1/03

SYSTEM THEORY OF OPERATION

XPhase

The XPhase

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 1, the XPhase

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

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.

0.1uF

CIN

CCS RCS

CCS RCS

0.1uF

VOUT+

VOUT SENSE-

VOUT-

12V

VID3

VID0

VID2

VID4

VOUT SENSE+

POWER GOOD

VR HOT

ENABLE

VID1

VID5

PHASE FAULT

IR3081

CONTROL

IC

>> BIAS VOLTAGE

>> PHASE TIMING

>> PWM CONTROL

<< CURRENT SENSE

ADDITIONAL PHASES

INPUT/OUTPUT

IR3086

PHASE

IC

CONTROL BUS

COUT

CURRENT SHARE

CURRENT SHARE

IR3086

PHASE

IC

>> VID VOLTAGE

PHASE FAULT

PHASE FAULT

PHASE HOT

PHASE HOT

Figure 1 – System Block Diagram