LTC3448 Ver la hoja de datos (PDF) - Linear Technology

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Fabricante

LTC3448

1.5MHz/2.25MHz, 600mA Synchronous Step-Down Regulator with LDO Mode

Linear Technology 

FEATURES

■ High Efficiency: Up to 96%

■ Very Low Quiescent Supply Current: 32µA During

Linear Regulator Operation

■ 600mA Output Current (Buck Converter)

■ Optionally Operates as Linear Regulator Below

3mA—External or Automatic ON/OFF

■ 2.5V to 5.5V Input Voltage Range

■ 1.5MHz or 2.25MHz Constant Frequency Operation

or External Synchronization

■ No Schottky Diode Required

■ Low Dropout Operation: 100% Duty Cycle

■ 0.6V Reference Allows Low Output Voltages

■ Shutdown Mode Draws < 1µA Supply Current

■ Current Mode Operation for Excellent Line and

Load Transient Response

■ Overtemperature Protected

■ Low Profile (3mm × 3mm) 8-Lead DFN and 8-Lead

MSOP Packages

U

APPLICATIO S

■ Cellular Telephones

■ Personal Information Appliances

■ Wireless and DSL Modems

■ Digital Still Cameras

■ MP3 Players

■ Portable Instruments

, LTC and LT are registered trademarks of Linear Technology Corporation.

All other trademarks are the property of their respective owners.

Protected by U.S. Patents including 5481178, 6580258, 6304066, 6127815,

6498466, 6611131. Others pending.

LTC3448

1.5MHz/2.25MHz, 600mA

Synchronous Step-Down

Regulator with LDO Mode

DESCRIPTIO

The LTC®3448 is a high efficiency, monolithic, synchronous

buck regulator using a constant frequency, current mode

architecture. Supply current during operation is only 32µA

(linear regulator mode) and drops to <1µA in shutdown. The

2.5V to 5.5V input voltage range makes the LTC3448 ide-

ally suited for single Li-Ion battery-powered applications.

100% duty cycle provides low dropout operation, extend-

ing battery life in portable systems. At moderate output load

levels, PWM pulse skipping mode operation provides very

low output ripple voltage for noise sensitive applications.

The LTC3448 automatically switches into linear regulator

operation at very low load currents to maintain <5mVP-P

output voltage ripple. Supply current in this mode is

typically 32µA. The switch to linear regulator mode occurs

at a threshold of 3mA. Linear regulator operation can be set

to on, off or automatic turn on/off.

Switching frequency is selectable at either 1.5MHz or

2.25MHz, allowing the use of small surface mount induc-

tors and capacitors.

The internal synchronous switch increases efficiency and

eliminates the need for an external Schottky diode. Low

output voltages are easily supported with the 0.6V feed-

back reference voltage. The LTC3448 is available in a low

profile 3mm × 3mm DFN package or thermally enhanced

8-lead MSOP.

TYPICAL APPLICATIO

1.5V High Efficiency Regulator with Automatic LDO Mode

VIN

2.5V TO 5.5V

CIN

4.7µF

VIN

SW

RUN VOUT

LTC3448

MODE

FREQ VFB

SYNC

GND

2.2µH

22pF 474k

316k

COUT

4.7µF

VOUT

1.5V

3448 TA01a

Efficiency and Power Loss vs Load Current

100 VIN = 3.6V

1

90 VOUT = 1.5V

80 TA = 25°C

0.1

70

EFFICIENCY

60

POWER LOSS

50

0.01

40

30

0.001

20

10

0

0.0001

0.001

0.01

0.1

0.0001

1

LOAD CURRENT (A)

23448 TA01b

3448f

1

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