1

LTC3405

3405fa

During Operation

Load Transient Response

The LTC

nous buck regulator 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 LTC3405 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 internal synchronous switch increases efficiency and

eliminates the need for an external Schottky diode. Low

output voltages are easily supported with the 0.8V feed-

back reference voltage. The LTC3405 is available in a low

profile (1mm) ThinSOT package.

For new designs, refer to the LTC3405A data sheet. For

fixed 1.5V and 1.8V output versions, refer to the

LTC3405A-1.5/LTC3405A-1.8 data sheet.

Figure 1a. High Efficiency Step-Down Converter

1.5MHz, 300mA

Synchronous Step-Down

Regulator in ThinSOT

Figure 1b. Efficiency vs Load Current

2.2µF

CER

2.7V

TO 5.5V

*

**

†

††

LTC3405

RUN

MODE

3

4.7µH**

22pF

887k

280k

3405 F01a

MURATA LQH3C4R7M34

TAIYO YUDEN LMK212BJ225MG

AVX TPSB336K006R0600

5

4

6

1

2

SW

GND

33µF

3.3V

+

, 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.

OUTPUT CURRENT (mA)

0.1

10

1000

100

95

90

85

80

75

70

65

60

3405 F01b

1

100

APPLICATIO S

FEATURES

TYPICAL APPLICATIO

DESCRIPTIO