LTC3548EDD(RevA) View Datasheet(PDF) - Linear Technology

Part Name

Description

MFG CO.

LTC3548EDD
(Rev.:RevA)

Dual Synchronous, 400mA/800mA, 2.25MHz Step-Down DC/DC Regulator

Linear Technology 

LTC3548

Dual Synchronous,

400mA/800mA, 2.25MHz

Step-Down DC/DC Regulator

FEATURES

n High Efficiency: Up to 95%

n Very Low Quiescent Current: Only 40μA

n 2.25MHz Constant Frequency Operation

n High Switch Current: 0.7A and 1.2A

n No Schottky Diodes Required

n Low RDS(ON) Internal Switches: 0.35Ω

n Current Mode Operation for Excellent Line

and Load Transient Response

n Short-Circuit Protected

n Low Dropout Operation: 100% Duty Cycle

n Ultralow Shutdown Current: IQ < 1μA

n Output Voltages from 5V down to 0.6V

n Power-On Reset Output

n Externally Synchronizable Oscillator

n Small Thermally Enhanced MSOP and 3mm × 3mm

DFN Packages

APPLICATIONS

■ PDAs/Palmtop PCs

■ Digital Cameras

■ Cellular Phones

■ Portable Media Players

■ PC Cards

■ Wireless and DSL Modems

DESCRIPTION

The LTC®3548 is a dual, constant frequency, synchronous

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

Mode® operation provides high efficiency at light loads,

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.

, 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.

TYPICAL APPLICATION

VIN = 2.8V

TO 5.5V

10μF

VOUT2 = 2.5V

AT 400mA

4.7μH

68pF

RUN2 VIN RUN1

MODE/SYNC

POR

LTC3548

SW2

SW1

100k

RESET

2.2μH

33pF

VOUT1 = 1.8V

AT 800mA

4.7μF

887k

280k

VFB2

GND

VFB1

604k

301k

10μF

3548 TA01

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

LTC3548 Efficiency Curve

100

1000

95

90

EFFICIENCY

100

85

80

10

POWER LOSS

75

70

65

60

1

1

VIN = 3.3V, VOUT = 1.8V

Burst Mode OPERATION

CHANNEL 1, NO LOAD ON CHANNEL 2 0.1

10

100

1000

LOAD CURRENT (mA)

3548 TA02

3548fa

1

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