LTC3548

1

3548fa

TYPICAL APPLICATION

FEATURES

APPLICATIONS

DESCRIPTION

, LTC, LT, LTM and Burst Mode are registered trademarks 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.

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PDAs/Palmtop PCs

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Digital Cameras

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Cellular Phones

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Portable Media Players

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PC Cards

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Wireless and DSL Modems

and Load Transient Response

DFN Packages

Dual Synchronous,

400mA/800mA, 2.25MHz

Step-Down DC/DC Regulator

step down DC/DC converter. Intended for low power ap-

plications, it operates from 2.5V 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 ≤1.2mm. Each output voltage is adjustable

from 0.6V to 5V. Internal synchronous 0.35Ω, 0.7A/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

while Pulse Skip Mode provides low noise ripple at light

loads.

To further maximize battery runtime, the P-channel

MOSFETs are turned on continuously in dropout (100%

duty cycle), and both channels draw a total quiescent cur-

rent of only 40μA. In shutdown, the device draws <1μA.

Figure 1. 2.5V/1.8V at 400mA/800mA Step-Down Regulators

RUN2

TO 5.5V

AT 400mA

AT 800mA

RUN1

POR

SW1

GND

SW2

MODE/SYNC

LTC3548

10μF

100k

RESET

33pF

68pF

2.2μH

4.7μH

887k

604k

301k

280k

4.7μF

10μF

3548 TA01

LOAD CURRENT (mA)

1

100

95

90

85

80

75

70

65

60

1000

100

10

1

0.1

10

100

1000

3548 TA02

Burst Mode OPERATION

CHANNEL 1, NO LOAD ON CHANNEL 2

POWER LOSS

EFFICIENCY

LTC3548 Efficiency Curve