1

LTC3403

3403f

APPLICATIO S

TYPICAL APPLICATIO

s

WCDMA Cell Phone Power Amplifiers

s

Wireless Modems

Figure 1a. WCDMA Transmitter Power Supply

Figure 1b. Efficiency vs Output Current

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

Burst Mode is a registered trademark of Linear Technology Corporation.

†

10

µF

CER

2.7V

TO 5V

*

**

†

LTC3403

RUN

REF

2.2

µH*

3403 F01a

MURATA LQH32CN2R2M11

TAIYO YUDEN JMK212BJ475MG

TAIYO YUDEN JMK212BJ106MN

3

SW

MODE

GDR

GND

4.7

µF

CER

3

600mA

WCDMA

RF PA

OUTPUT

PROGRAMMING

DAC

OUTPUT CURRENT (mA)

60

70

75

85

95

0.1

10

100

1000

3403 F01b

50

1

80

65

55

90

FORCED

CONTINUOUS

MODE

Burst Mode

OPERATION

1.5MHz, 600mA

Synchronous Step-Down

Regulator with Bypass Transistor

DESCRIPTIO

FEATURES

s

Dynamically Adjustable Output from 0.3V to 3.5V

s

Very Low Quiescent Current: Only 20

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 < 1

µA 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

The LTC

nous buck regulator optimized for WCDMA power ampli-

fier applications. The output voltage can be dynamically

eliminating power loss through the inductor. Selectable

controlling input.

Supply current is only 20

drops to <1

µA 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.