LTC3548-2 Linear Technology, LTC3548-2 Datasheet

LTC3548-2

Manufacturer Part Number

LTC3548-2

Description

Step-Down DC/DC Regulator

Manufacturer

Linear Technology

Datasheet

1.LTC3548-2.pdf (16 pages)

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FEATURES

■

APPLICATIO S

■

400mA

TYPICAL APPLICATIO

OUT2

2.5V

High Efficiency: Up to 95%

1.8V/800mA Fixed Output and 400mA Adjustable

Output Voltage

Only 40µA Quiescent Current (Both Channels)

2.25MHz Constant Frequency Operation

High Switch Current Limits: 1.2A and 0.7A

No Schottky Diodes Required

Low R

Current Mode Operation for Excellent Line

and Load Transient Response

Short-Circuit Protected

Low Dropout Operation: 100% Duty Cycle

Ultralow Shutdown Current: I

Power-On Reset Output

Externally Synchronizable Oscillator

Small Thermally Enhanced 3mm × 3mm DFN Package

PDAs/Palmtop PCs

Digital Cameras

Cellular Phones

Portable Media Players

PC Cards

Wireless and DSL Modems

2.8V TO 5.5V

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

DS(ON)

4.7µF

68pF

887k

Internal Switches: 0.35Ω

280k

10µF

4.7µH

MODE/SYNC

SW2

RUN2

FB2

LTC3548-2

GND

< 1µA

RUN1

SW1

POR

OUT1

Fixed/Adjustable Output, 2.25MHz

2.2µH

100k

RESET

35482 F01

Step-Down DC/DC Regulator

10µF

1.8V

800mA

OUT1

DESCRIPTIO

The LTC

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

applications, 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. For channel 1, the output voltage

is fixed at 1.8V/800mA; for channel 2, the output voltage

is adjustable from 0.6V to V

0.35Ω, 1.2A/0.7A 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

while Pulse Skip Mode provides low noise ripple at light

loads.

To further maximize battery run time, 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.

trademarks are the property of their respective owners. Burst Mode is a registered

trademark of Linear Technology Corporation. Protected by U.S. Patents including 5481178,

6580258, 6304066, 6127815, 6498466, 6611131.

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

operation provides high efficiency at light loads,

3548-2 is a dual, constant frequency, synchro-

100

Efficiency and Power Loss

Dual Synchronous,

EFFICIENCY

vs Load Current

LOAD CURRENT (mA)

POWER LOSS

Burst Mode OPERATION

CHANNEL 1

NO LOAD ON CHANNEL 2

OUT

= 3.6V

= 1.8V

100

. Internal synchronous

LTC3548-2

35482 F01b

1000

100

0.1

35482f

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