LTC3407EDD-3 データシートの表示（PDF） - Linear Technology

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LTC3407EDD-3

Dual Synchronous, 1.8V/0.8A and 3.3V/0.8A 2.25MHz Step-Down DC/DC Regulator

Linear Technology 

LTC3407-3

Dual Synchronous,

1.8V/0.8A and 3.3V/0.8A

2.25MHz Step-Down DC/DC Regulator

FEATURES

■ Very Low Quiescent Current: Only 40µA

■ 1.8V at 800mA/3.3V at 800mA

■ High Efficiency: Up to 95%

■ 2.25MHz Constant Frequency Operation

■ High Switch Current: 1.2A on Each Channel

■ No Schottky Diodes Required

■ Low RDS(ON) Internal Switches: 0.35Ω

■ VIN: 3.3V to 5.5V

■ Current Mode Operation for Excellent Line

and Load Transient Response

■ Short-Circuit Protected

■ Low Dropout Operation: 100% Duty Cycle

■ Ultralow Shutdown Current: IQ < 1µA

■ Power-On Reset Output

■ Externally Synchronizable Oscillator

■ Small Thermally UEnhanced 3mm × 3mm DFN Package

APPLICATIO S

■ PDAs/Palmtop PCs

■ Digital Cameras

■ Cellular Phones

■ Portable Media Players

■ PC Cards

■ Wireless and DSL Modems

DESCRIPTIO

The LTC®3407-3 is a dual, constant frequency, synchro-

nous step down DC/DC converter. Intended for low power

applications, it operates from 3.3V to 5.5V input voltage

range and has a constant 2.25MHz switching frequency,

allowing the use of tiny, low cost capacitors and inductors

with a profile ≤1.0mm. Internal synchronous 0.35Ω, 1.2A

power switches provide high efficiency without the need

for external Schottky diodes.

A user selectable mode input is provided to allow the user

to trade-off noise ripple for low power efficiency. Burst

Mode® operation provides high efficiency at light loads,

while Pulse Skip Mode provides low noise ripple at light

loads.

To further maximize battery life, the P-channel MOSFETs

are turned on continuously in dropout (100% duty cycle),

and both channels draw a total quiescent current of only

40µA. In shutdown, the device draws <1µA.

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

Burst Mode is a registered trademark 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.

TYPICAL APPLICATIO

VIN

3.3V TO 5.5V

VOUT2

3.3V

10µF

2.2µH

10µF

RUN2 VIN RUN1

MODE/SYNC

POR

LTC3407-3

SW2

SW1

VOUT2

GND

VOUT1

100k

RESET

2.2µH

VOUT1

1.8V

10µF

34073 TA01

NOTE: IN DROPOUT, THE OUTPUT TRACKS THE INPUT VOLTAGE

Figure 1. 1.8V/3.3V at 800mA Step-Down Regulators

LTC3407-3 Efficiency/Power Loss

100

90

80

70

60

50

40

30

20

10

1

1

VOUT = 3.3V

VOUT = 1.8V

0.1

VOUT = 3.3V VOUT = 1.8V

0.01

0.001

VIN = 5V

Burst Mode OPERATION

NO LOAD ON OTHER CHANNEL

0.000

10

100

1000

LOAD CURRENT (mA)

34073 TA01b

34073fa

1

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