MP3908 – HIGH EFFICIENCY BOOST CONTROLLER

MP3908 Rev.0.9

www.MonolithicPower.com

9

8/29/2008

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In cases where the ESR zero is in a relatively

low frequency region and results in insufficient

gain margin, an optional capacitor (C5) (shown

in flat page) should be added. Then a pole,

formed by C5 and R3, should be placed at the

ESR zero to cancel the adverse effect.

R3

2

1

5

C

×

×

π

×

=

Layout Consideration

High frequency switching regulators require

very careful layout for stable operation and low

noise. Keep the high current path as short as

possible between the MOSFET drain, output

diode, output capacitor and GND pin for

must be placed close to the VCC pin for best

decoupling. All feedback components must be

kept close to the FB pin to prevent noise

injection on the FB pin trace. The ground return

of the input and output capacitors should be

tied closed to the GND pin. See the MP3908

demo board layout for reference.