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续流用的，开关和电感同时作用，
& U6 s0 ~1 _% ?3 A' q/ \! _$ KWith the PFET on, the input supply charges COUT and
) r2 q4 L' u; d) H/ [4 E' nsupplies current to the load via the series path through the0 L" R- l& A5 n+ b
PFET and the inductor. Current through the Inductor ramps; s ]: H0 K9 B8 B1 u) ^0 a
up linearly and the output voltage increases. As the FB voltage
, \6 D' F9 ~5 F L% A+ G8 Ireaches the upper threshold, which is the internal reference$ s! i( \" h9 p1 j# m2 c$ B
voltage plus 10mV, the output of the comparator
& n5 `9 f3 ] p4 [* f) schanges from low to high, and the PGATE responds by turning2 X: [8 _6 }( N3 F+ K6 ~
the PFET off. As the PFET turns off, the inductor voltage
, o3 b- d6 w; x/ freverses, the catch diode turns on, and the current through
Y! ?& r: B2 H1 q& E5 Fthe inductor ramps down. Then, as the output voltage reaches1 L& D" W+ Z; p" [" J4 ]" k
the internal reference voltage again, the next cycle starts |
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发表于 2011-6-10 10:08
