LTC3541EDD-3 查看數據表（PDF） - Linear Technology

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LTC3541EDD-3

High Efficiency Buck + VLDO Regulator

Linear Technology 

LTC3541-3

High Efficiency

Buck + VLDO Regulator

FEATURES

DESCRIPTIO

■ High Efficiency 500mA Buck Plus 300mA VLDO

Regulator

Auto Start-Up Powers VLDO/Linear Regulator

Output Prior to Buck 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: 1.8V

■ VLDO Input Voltage Range (LVIN: 1.675V to 5.5V)

■ Fixed VLDO Output Voltage: 1.575V

■ 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®3541-3 combines a synchronous buck DC/

DC converter with a very low dropout linear regulator

(VLDOTM regulator) and internal feedback resistor networks

to provide two output voltages from a single input voltage

with minimum external components. When configured

for dual output operation, the LTC3541-3’s auto start-up

feature will bring the 1.575V VLDO/linear regulator output

into regulation in a controlled manner prior to enabling the

1.8V buck output without the need for external pin control.

The 300mA VLDO/linear regulator output will source only

30mA until the buck output achieves regulation. The input

voltage range is ideally suited for applications powered

from a Li-Ion battery and 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 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

LTC3541-3 Typical Application

VIN

3V TO 5V

2.2µH

VOUT1

1.8V

10µF

SW ENVLDO

VIN

MODE

LTC3541-3

ENBUCK GND

VOUT

LVIN

LVOUT

PGND

VOUT2

1.575V

2.2µF

35413 TA01a

Buck (Burst) Efficiency vs Load Current

100

1

VIN = 3V

90

EFFICIENCY

80

0.1

70

60

50

POWER

0.01

LOSS

40

30

0.001

20

10

0

0.0001

1

10

100

1000

LOAD CURRENT (mA) 35413 TA01b

35413fc



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