Fast PFET Buck Controller
LM51031
A P−Ch FET with a continuous drain current (ID)
rating greater than the maximum output current is
required. The Gate−to−Source voltage VGS and
Source Breakdown Voltage should be chosen
based on the input supply voltage. The power
dissipation due to the conduction losses is
given by:
where
The power dissipation of the P−Ch FET due to
the switching losses is given by:
where tr = Rise Time.
11) Diode Selection
The flyback or catch diode should be a Schottky
diode because of it’s fast switching ability and
low forward voltage drop. The current rating
must be at least equal to the maximum output
current. The breakdown voltage should be at
least 20 V for this 12 V application. The diode
power dissipation is given by:
HTC
− 9 −
HTC [ HTC KOREA TAEJIN TECHNOLOGY CO. ]
