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

MP2930 Rev. 1.01

www.MonolithicPower.com

19

10/30/2013

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lowest switching frequency that allows the

regulator

to

meet

the

transient-response

requirements.

Selecting the Input Capacitor

The

input

capacitors

are

responsible

for

sourcing the AC component of the input current

flowing into the upper MOSFETs. Their RMS

current capacity must be sufficient to handle the

AC component of the current drawn by the

upper MOSFETs which is related to duty cycle

and the number of active phases.

Low

capacitance,

high-frequency

ceramic

capacitors are needed in addition to the bulk

capacitors to suppress leading and falling edge

voltage

spikes.

Select

low

ESL

ceramic

capacitors and place one as close as possible

to each upper MOSFET drain to minimize board

parasitic

impedances

and

maximize

suppression.

PC Board Layout

For best performance of the MP2930, the

following guidelines should be strictly followed:

Within the allotted implementation area, place

the

switching

components

first.

Switching

component placement should take into account

power dissipation. Align the output inductors

and MOSFETs such that space between the

components is minimized while creating the

PHASE plane. If possible, duplicate the same

placement of these components for each phase.

Next, place the input and output capacitors.

Position one high frequency ceramic input

capacitor next to each upper MOSFET drain.

Place the input capacitors as close to the upper

MOSFET drains as dictated by the component

size

and

dimensions.

Locate

the

output

capacitors between the inductors and the load,

while keeping them in close proximity to the

microprocessor socket.