LTC3541-2(RevA) データシートの表示（PDF） - Linear Technology
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LTC3541-2 Datasheet PDF : 20 Pages
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LTC3541-2
High Efficiency
Buck + VLDO Regulator
FEATURES
DESCRIPTIO
■ High Efficiency, 500mA Buck Plus 300mA VLDO
Regulator
Auto Start-Up Powers Buck Output Prior to VLDO/
Linear Regulator Output
■ Independent 500mA High Efficiency Buck
(VIN: 2.7V to 5.5V)
■ 300mA VLDO Regulator with 30mA Standalone Mode
■ No External Schottky Diodes Required
■ Fixed Buck Output Voltage: 1.875V
■ VLDO Input Voltage Range (LVIN: 1.6V to 5.5V)
■ Fixed VLDO Output Voltage: 1.5V
■ Selectable Fixed Frequency, Pulse-Skip Operation
or Burst Mode® Operation
■ Short-Circuit Protected
■ Current Mode Operation for Excellent Line and Load
Transient Response
■ Shutdown Current: <3µA
■ Constant Frequency Operation: 2.25MHz
■ Low Dropout Buck Operation: 100% Duty Cycle
■ Small, Thermally Enhanced, 10-Lead (3mm × 3mm)
DFN Package
U
APPLICATIO S
■ Digital Cameras
■ Cellular Phones
■ PC Cards
■ Wireless and DSL Modems
■ Other Portable Power Systems
The LTC®3541-2 combines a synchronous buck DC/
DC converter with a very low dropout linear regulator
(VLDOTMregulator) and internal feedback resistor networks
to provide two output voltages from a single input volt-
age with minimal external components. When configured
for dual output operation, the LTC3541-2’s auto start-up
feature will bring the 1.875V buck output into regulation
in a controlled manner, prior to enabling the 1.5V VLDO
output without the need for external pin control. The
1.5V VLDO/linear regulator output prior to 1.875V buck
output sequencing may also be obtained via external pin
control. The input voltage range is ideally suited for Li-Ion
battery applications powering sub-3.3V logic from 5V or
3.3V rails.
The synchronous buck converter provides a high efficiency
output, typically 90%. It can provide up to 500mA of output
current while switching at 2.25MHz, allowing the use of
small surface mount inductors and capacitors. A mode-
select pin allows Burst Mode operation to be enabled for
higher efficiency at light load currents, or disabled for lower
noise, constant frequency operation.
The VLDO regulator provides a low noise, low voltage
output capable of providing up to 300mA of output current
using only a 2.2µF ceramic capacitor. The input supply
voltage of the VLDO regulator (LVIN) may come from the
buck regulator output or a separate supply.
, LT, LTC, LTM and Burst Mode are registered trademarks of Linear Technology
Corporation. VLDO is a trademark of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
Protected by U.S. Patents, including 5481178, 6611131, 6304066, 6498466, 6580258.
TYPICAL APPLICATIO
VIN
2.9V TO 5.5V
2.2µH
VOUT1
1.875V
200mA
10µF
SW ENVLDO
VIN
MODE
LTC3541-2
ENBUCK GND
VOUT
LVIN
LVOUT
PGND
VOUT2
1.5V
2.2µF 300mA
35412 TA01a
Buck (Burst) Efficiency vs Load Current
100
1
VIN = 3V
90
EFFICIENCY
80
0.1
70
60
POWER LOSS
50
0.01
40
30
0.001
20
10
0
0.0001
1
10
100
1000
LOAD CURRENT (mA) 35412 TA01b
35412fb
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