MP2930 - 4-PHASE PWM CONTROLLER WITH 8-BIT DAC CODE

MP2930 Rev. 1.01

www.MonolithicPower.com

10

10/30/2013

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OPERATION

Multiphase Power Conversion

The MP2930 is a multiphase regulators and it

can be programmed for 2-, 3- or 4-channel

operation

for

microprocessor

core.

The

switching of each channel in a multiphase

converter is timed to be symmetrically out-of-

phase with each of the other channels. The

interleaving work of each phase can help to

reduce of ripple current amplitude and to

reduce input ripple current.

PWM Operation

Under steady state conditions the operation of

the

MP2930

appears

to

be

that

of

a

conventional

trailing

edge

modulator.

Conventional analysis and design methods can

be used for steady state and small signal

operation.

Under load transition condition, the MP2930

can turn on all phase together to improve the

load transient. It can achieve excellent transient

performance and reduce the demand on the

output capacitors.

The default channel setting for the MP2930 is

four and the timing of each channel is set by the

number of active channels. The cycle time of

the pulse signal is the inverse of the switching

frequency set by the resistor between the FS

pin and GND.

For 4-channel operation, the channel firing

order is 4-3-2-1: PWM3 pulse happens 1/4 of a

cycle

after

PWM4,

PWM2

output

follows

another 1/4 of a cycle after PWM3, and PWM1

delays another 1/4 of a cycle after PWM2. For

3-channel operation, the channel firing order is

3-2-1.

Connecting PWM4 to VCC selects 3-phase

operation and the pulse times are spaced in 1/3

cycle increments. If PWM3 is connected to VCC,

2-phase operation is selected and the PWM2

pulse happens 1/2 of a cycle after PWM pulse.

Switching Frequency

The MP2930 switching frequency is set by the

Equation (1).

SW

10

T

F

10

2.5

R





(1)

phase.

Current Sensing

MP2930 has cycle by cycle current sense for

fast response. MP2930 adopts inductor DCR

sensing, or resistive sensing techniques. The

inductor current. The sensed current is used for

current

balance,

load-line

regulation,

and

overcurrent protection.

Inductor DCR Sensing

The MP2930 can adopt a lossless current

sensing scheme, commonly referred to as

inductor DCR sensing, as shown in Figure 2.

Figure 2

—DCR Sensing Configuration

Equation (2) shows the s-domain equivalent





DCR

L

s

L

I

L

V









(2)

A simple RC network across the inductor

extracts the DCR voltage, as shown in Figure 2.







RC

s

L

I

DCR

1

DCR

L

s

C

V



























(3)