SC2440 SEMTECH [Semtech Corporation], SC2440 Datasheet - Page 14

• Manufacturer Part Number: SC2440
• Description: 2.5 MHz Dual Switching Regulator with Integrated 2A Switches
• Manufacturer: SEMTECH [Semtech Corporation]

The switch base current
are the switch emitter current and current gain
respectively, is drawn from the bootstrap capacitor C
Charge
time, resulting in a voltage droop of
T
will be 0.57V. C
cycle, where
base current discharges the bootstrap capacitor to
difference between this voltage and that at SW must be
POWER MANAGEMENT
Applications Information
V
ON
A
2005 Semtech Corp.
= 1 s,
V
D
BST
I
VS > 2.5V
SW
VIN
VIN
â
T
V
ON
D
RECT
V is the applied D
A
35 and C
is drawn from C
BST
MAX V
I
DBST
is refreshed to
SW
IN
IN
C
T
BST
SC2440
SC2440
ON
BST
BOOST
BOOST
BST
GND
GND
=
at the end of conduction. The
MAX V
V
= 0.1 F, then the
I
N
â
+
I
SW
SW
V
SW
OUT
(a)
BST
(c)
1
BST
BST
=
Figure 8. Methods of Bootstrapping the SC2440.
V
anode voltage. Switch
I
V
I
during the switch on
N
SW
â
A
+
D
I
D
âC
V
SW
RECT
, where I
RECT
S
V
CBST
CBST
T
BST
D
DBST
ON
BST
. If I
V
V
C
D
BST
SW
RECT
SW
and
VOUT
VOUT
droop
= 2A,
every y
BST
.
14
higher than the minimum shown in Figure 7 to maximize
efficiency. D
output of the DC/DC converter.
If
the input power supply will be
of the switch). The energy loss due to base charge per
cycle is
If
the output capacitor will still be
due to base charge per cycle is
VS > VIN + 2.5V
D
D
BST
BST
VIN
VIN
is tied to the output, then the charge drawn from
is tied to the input, then the charge drawn from
I
SW
V
BST
IN
DBST
DBST
T
IN
IN
ON
can be tied either to the input or to the
SC2440
SC2440
for a power loss of
BOOST
BOOST
GND
GND
MAX V
MAX V
(b)
(d)
SW
SW
BST
BST
=
=
V
2V
S
I
N
I
SW
I
D
I
D
SW
SW
RECT
RECT
T
CBST
ON
T
V
ON
OUT
DI
(the base charge
. The energy loss
T
SW
www.semtech.com
ON
SC2440
V
IN
for a power
VOUT
VOUT
I
SW
V
OUT
.