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LTZQ

1.5V, 1.8V, 1.5MHz, 300mA Synchronous Step-Down Regulators in ThinSOT

Linear Technology 

LTC3405A-1.5/LTC3405A-1.8

1.5V, 1.8V, 1.5MHz, 300mA

Synchronous Step-Down

Regulators in ThinSOT

FEATURES

■ High Efficiency: Up to 93%

■ Very Low Quiescent Current: Only 20µA

During Operation

■ 300mA Output Current at VIN = 3V

■ 2.5V to 5.5V Input Voltage Range

■ 1.5MHz Constant Frequency Operation

■ No Schottky Diode Required

■ Low Dropout Operation: 100% Duty Cycle

■ Stable with Ceramic Capacitors

■ Shutdown Mode Draws < 1µA Supply Current

■ ±3% Output Voltage Accuracy

■ Current Mode Operation for Excellent Line and

Load Transient Response

■ Overtemperature Protected

■ Low Profile (1mm) ThinSOTTM Package

U

APPLICATIO S

■ Cellular Telephones

■ Personal Information Appliances

■ Wireless and DSL Modems

■ Digital Still Cameras

■ MP3 Players

■ Portable Instruments

TYPICAL APPLICATIO

VIN

2.7V

TO 5.5V

CIN**

4.7µF

CER

4

VIN

3 4.7µH*

SW

LTC3405A-1.8

1

RUN

6

5

MODE VOUT

GND

2

3405A1518 F01

*MURATA LQH3C4R7M34

**TAIYO YUDEN JMK212BJ475MG

VOUT

1.8V

300mA

COUT**

4.7µF

CER

Figure 1a. High Efficiency Step-Down Converter

DESCRIPTIO

The LTC®3405A-1.5/LTC3405A-1.8 are high efficiency

monolithic synchronous buck regulators using a constant

frequency, current mode architecture. Supply current

during operation is only 20µA and drops to <1µA in

shutdown. The 2.5V to 5.5V input voltage range makes the

LTC3405A-1.5/LTC3405A-1.8 ideally suited for single

Li-Ion battery-powered applications. 100% duty cycle

provides low dropout operation, extending battery life in

portable systems.

Switching frequency is internally set at 1.5MHz, allowing

the use of small surface mount inductors and capacitors.

The LTC3405A-1.5/LTC3405A-1.8 are specifically designed

to work well with ceramic output capacitors, achieving

very low output voltage ripple and a small PCB footprint.

The internal synchronous switch increases efficiency and

eliminates the need for an external Schottky diode. The

LTC3405A-1.5/LTC3405A-1.8 are available in a low profile

(1mm) ThinSOT package.

For adjustable output voltage, refer to the LTC3405A data

sheet.

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

ThinSOT is a trademark of Linear Technology Corporation.

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

100

VIN = 2.7V

90

80

VIN = 3.6V

VIN = 4.2V

70

VIN = 5.5V

60

50

40

0.1

1

10

100

OUTPUT CURRENT (mA)

1000

3405A1518 F01b

Figure 1b. Efficiency vs Load Current

3405a1518fa

1

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