LTC3403EDD View Datasheet(PDF) - Linear Technology

Part Name

Description

MFG CO.

LTC3403EDD

1.5MHz, 600mA Synchronous Step-Down Regulator with Bypass Transistor

Linear Technology 

LTC3403

1.5MHz, 600mA

Synchronous Step-Down

Regulator with Bypass Transistor

FEATURES

s Dynamically Adjustable Output from 0.3V to 3.5V

s Very Low Quiescent Current: Only 20µA

During Operation

s 600mA Output Current

s Internal P-Channel MOSFET Bypass Transistor

s High Efficiency: Up to 96%

s 1.5MHz Constant Frequency Operation

s No Schottky Diode Required

s Low Dropout Operation: 100% Duty Cycle

s 2.5V to 5V Input Voltage Range

s Drives Optional External P-Channel MOSFET

s Shutdown Mode Draws < 1µA Supply Current

s Current Mode Operation for Excellent Line and

Load Transient Response

s Overtemperature Protected

s Available in 8-Lead 3mm × 3mm DFN Package

U

APPLICATIO S

s WCDMA Cell Phone Power Amplifiers

s Wireless Modems

DESCRIPTIO

The LTC®3403 is a high efficiency monolithic synchro-

nous buck regulator optimized for WCDMA power ampli-

fier applications. The output voltage can be dynamically

programmed from 0.3V to 3.5V. At VOUT > 3.6V an internal

bypass P-channel MOSFET connects VOUT directly to VIN,

eliminating power loss through the inductor. Selectable

forced continuous mode enables fast VOUT response to the

controlling input.

Supply current is only 20µA in Burst Mode® operation and

drops to <1µA in shutdown. The 2.5V to 5V input voltage

range makes the LTC3403 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.

The LTC3403 is available in a low profile 8-lead 3mm ×

3mm DFN package.

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

Burst Mode is a registered trademark of Linear Technology Corporation.

TYPICAL APPLICATIO

VIN

2.7V

TO 5V

OUTPUT

PROGRAMMING

DAC

CIN†

10µF

CER

VIN

SW

LTC3403

MODE GDR

RUN VOUT

REF

GND

3

2.2µH*

*MURATA LQH32CN2R2M11

**TAIYO YUDEN JMK212BJ475MG

†TAIYO YUDEN JMK212BJ106MN

COUT**

4.7µF

CER

VOUT

3× VREF

600mA

WCDMA

RF PA

3403 F01a

Figure 1a. WCDMA Transmitter Power Supply

95

90

VIN = 3.6V

85

VIN = 4.2V

80

VIN = 3.6V

75

VIN = 4.2V

70

65

60

55

50

0.1

FORCED

CONTINUOUS

MODE

Burst Mode

OPERATION

VOUT = 1.8V

1

10

100

OUTPUT CURRENT (mA)

1000

3403 F01b

Figure 1b. Efficiency vs Output Current

3403f

1

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