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L3380 Schematic ( PDF Datasheet ) - Unisonic Technologies

Teilenummer L3380
Beschreibung PWM STEP UP DC-DC CONTROLLER
Hersteller Unisonic Technologies
Logo Unisonic Technologies Logo 




Gesamt 9 Seiten
L3380 Datasheet, Funktion
UNISONIC TECHNOLOGIES CO., LTD
L3380
PWM STEP UP DC-DC
CONTROLLER
CMOS IC
DESCRIPTION
The L3380 is PWM step up DC-DC switching controller that
operates from 0.9V. The low start up input voltage makes L3380
specially designed for powering portable equipment from one or two
cells battery packs. This device consist of a soft start circuit, a
reference voltage source, an error amplifier, an oscillator, a phase
compensation, a PWM controller and an output drive circuit for
driving external power transistor.
Additionally, a chip enable feature is provided to power down the
converter for extended battery life. The device features a voltage
mode PWM control loop, providing stable and high efficiency
operation over a broad load current range.
FEATURES
* 0.9V low start-up Input voltage at 1mA load
* Low operation current
* 0.5uA low shutdown current
* Fix requency PWM at 100KHZ
www.DataSheet4U.com
* Built in PWM switching control circuit ,duty ratio is 0~83%
* Output voltage:0.1V step setting is available between 2.0V and
6.5V
* Soft start time: 6ms
* Shutdown function
APPLICATIONS
*Portable devices
*Electronic games
*Portable audio (MP3)
*Personal digital assistant (PDA)
*Digital still cameras(DSC)
*Camcorders
*White LED driver
*Single and dual-cell battery operated products
ORDERING INFORMATION
Order Number
Normal
Lead Free Plating
L3380-xx-AF5-R
L3380L-xx-AF5-R
Package
SOT-25
1
2
3
5
4
SOT-25
*Pb-free plating product number: L3380L
Packing
Tape Reel
L3380L-xx-AF5-R
(1)Packing Type
(2)Package Type
(3)Output Voltage Code
(4)Lead Plating
(1) R: Tape Reel
(2) AF5: SOT-25
(3) xx: refer to Marking Information
(4) L: Lead Free Plating, Blank: Pb/Sn
www.unisonic.com.tw
Copyright © 2006 Unisonic Technologies Co., Ltd
1 of 9
QW-R502-099,A






L3380 Datasheet, Funktion
L3380
CMOS IC
APPLICATION CIRCUIT INFORMATION
The following equations show the relation of the basic design parameters.
1. Refer to the application circuit, the increasing inductor current when the switch is turn on is given by the following
equation
iL+
=
1
L
U
LTON
=
1
L
(U
IN
US )
d
f
(U IN :input voltage ; U S :transistor saturation voltage)
The decreasing inductor current when the switch is turn off can derive by the equation below
iL
=
1
L
U
TL OFF
=
1
L
(U
O
+UD
U
IN
)
1
f
d
U D diode forward voltage
according to iL+ + ∆iL= 0 ,the duty ratio is given by
d
=
UO + U D U IN
UO +UD US
2. The average current flowing through the inductor is
IL
=
IO
1d
3. We note that IO = (1d )IL
then
we
can
write: IO
=
(1d )
IL
iL
• ∆iL
substituting
iL
=
1
L
U
TL OFF
iL
for equation above, output current is given by
IO
=
(1
d)
1
ICR
1
L
U
TL OFF
(
ICR
=
iL
IL
)
IO
=
(1
d)
1
ICR
1
L
(Uo + U D
U IN
)
1
f
d
IO=(1-d )2
UO+UD – UIN
ICR L f
derive that
L=
(1– d)2(UO+UD-UIN)
ICR IO f
4. The peak current of the inductor is given by
I PK
=
IL
+
1
2
iL
I PK
=
IL
+1
2
iL
IL
IL
according to
ICR
=
iL
IL
derive that
I PK
=
IL
+
1
2
ICR IL
Then derive the following equation for peak current of inductor
I PK
=
IL (1+
1
2
ICR)
UNISONIC TECHNOLOGIES CO., LTD
www.unisonic.com.tw
6 of 9
QW-R502-099,A

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