SC4524SETRT 查看數據表（PDF） - Semtech Corporation
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SC4524SETRT Datasheet PDF : 21 Pages
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SC4524
POWER MANAGEMENT
Applications Information
cycle is
ISW VINTON
b
for a power loss of
DISW VIN
b
» ISW VOUT
b
.
loss of
DISW VOUT
b
.
If D is tied to the output, then the charge drawn from
BST
the
output
capacitor
will
still
be
ISW TON
b
.
The
energy
loss
due to base charge per cycle is
ISW VOUT TON
b
for a power
Since VOUT < VIN, DBST should always be tied to VOUT (if
>2.5V) to maximize efficiency. In general efficiency
penalty increases as D decreases.
Figure 7 summarizes various ways of bootstrapping the
SC4524. A fast switching PN diode (such as 1N4148 or
MAX VBST = VIN + VOUT
DBST
BST
CBST
VIN
IN
SW
SC4524
GND
DRECT
VOUT
(a)
DBST DZ
= MAX VBST 2VIN - VZ
+ VZ -
BST
CBST
VIN
IN
SW
SC4524
GND
DRECT
VOUT
DBST
= MAX VBST 2VIN
BST
CBST
VIN
IN
SW
SC45 24
GND
DRECT
VOUT
(b)
VS > 2.5V
DBST
= MAX VBST VIN + VS
BST
CBST
VIN
IN
SW
SC4524
GND
D RECT
VOUT
(c)
(d)
= VS > VIN + 2.5V DBST MAX VBST VS
BST
VIN
IN
SW
SC45 24
GND
D RECT
VOUT
2006 Semtech Corp.
(d)
Figure 7. Methods of Bootstrapping the SC4524.
13
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