LTC3548EDD-2-TRPBF Просмотр технического описания (PDF) - Linear Technology

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LTC3548EDD-2-TRPBF

Dual Synchronous, Fixed /Adjustable Output, 2.25MHz Step-Down DC/DC Regulator

Linear Technology 

LTC3548-2

FEATURES

Dual Synchronous,

Fixed /Adjustable Output, 2.25MHz

Step-Down DC/DC Regulator

DESCRIPTION

n High Efficiency: Up to 95%

n 1.8V/800mA Fixed Output and 400mA Adjustable

Output Voltage

n Only 40μA Quiescent Current (Both Channels)

n 2.25MHz Constant-Frequency Operation

n High Switch Current Limits: 1.2A and 0.7A

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 Power-On Reset Output

n Externally Synchronizable Oscillator

n Small, Thermally Enhanced 3mm × 3mm DFN Package

APPLICATIONS

n PDAs/Palmtop PCs

n Digital Cameras

n Cellular Phones

n Portable Media Players

n PC Cards

n Wireless and DSL Modems

The LTC®3548-2 is a dual, constant-frequency, synchro-

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 VIN Internal synchronous 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® operation provides high efficiency at light

loads, while pulse-skipping 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 cur-

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

L, LT, LTC, LTM, Linear Technology, the Linear logo 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, 6127815, 6304066, 6498466, 6580258

6611131..

TYPICAL APPLICATION

VIN

2.8V TO 5.5V

10μF

VOUT2

2.5V

400mA

4.7μH

68pF

RUN2 VIN RUN1

MODE/SYNC

POR

LTC3548-2

SW2

SW1

100k

RESET

2.2μH

VOUT1

1.8V

800mA

887k

4.7μF

280k

VFB2

VOUT1

GND

10μF

35482 F01

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

Efficiency and Power Loss

vs Load Current

100

1000

95

90

EFFICIENCY

100

85

POWER LOSS

80

10

75

VIN = 3.6V

70

VOUT = 1.8V

1

Burst Mode OPERATION

65

CHANNEL 1

NO LOAD ON CHANNEL 2

60

0.1

1

10

100

1000

LOAD CURRENT (mA)

35482 F01b

35482fb

1

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