LTC3520 Ver la hoja de datos (PDF) - Linear Technology

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LTC3520

Synchronous 1A Buck-Boost and 600mA Buck Converters

Linear Technology 

LTC3520

Synchronous 1A

Buck-Boost and 600mA

Buck Converters

FEATURES

n Dual High Efficiency DC/DC Converters:

Buck-Boost (VOUT: 2.2V to 5.25V, IOUT = 1A at

VOUT = 3.3V, VIN ≥ 3V)

Buck (VOUT: 0.8V to VIN, IOUT = 600mA)

n 2.2V to 5.5V Input Voltage Range

n Pin-Selectable Burst Mode® Operation

n Uncommitted Gain Block for LDO Controller, Battery

Good Indication or Sequencing

n Programmable 100kHz to 2MHz Switching Frequency

n 55μA Total Quiescent Current for Both Converters in

Burst Mode Operation

n Thermal and Overcurrent Protection

n <1μA Quiescent Current in Shutdown

n 24-Lead 4mm × 4mm QFN Package

APPLICATIONS

n Portable Media Players

n Digital Cameras

n Handheld PCs, PDAs

n GPS Receivers

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, 6166527, 6304066, 6404251, 6580258.

DESCRIPTION

The LTC®3520 combines 1A buck-boost and 600mA

synchronous buck DC/DC converters in a tiny 4mm ×

4mm package. A programmable switching frequency

allows the efficiency to be optimized while minimizing

the solution footprint. Both converters feature soft-start

and current limit protection. The uncommitted gain block

can be configured as an LDO or utilized as a battery-good

comparator.

The buck converter is current mode controlled with internal

synchronous rectification to improve efficiency. Pin-select-

able Burst Mode operation can be enabled to improve light

load efficiency, or the buck converter can be operated in

low noise PWM mode for sensitive applications.

The buck-boost converter provides continuous conduc-

tion operation to maximize efficiency and minimize noise.

At light loads, use of Burst Mode operation will improve

efficiency.

The LTC3520 provides a <1μA shutdown mode and over-

temperature shutdown on both converters. The LTC3520

is available in a low profile (0.75mm) 24-lead 4mm ×

4mm QFN package.

TYPICAL APPLICATION

3.3V at 500mA, 1.8V at 600mA and 1.5V at 200mA Converter

VIN

2.2V TO

5.5V

VOUT2

1.8V

600mA

10μF

22μF

255k

200k

BURST

4.7μH

27pF

0.01μF

54.9k

PWM

PVIN1 PVIN2 PVIN3 SVIN SW1A

SW1B

SW2

VOUT1

VC1

FB2

SS2

FB1

LTC3520

SS1

RT

PWM1

PWM2

AOUT

4.7μH

470pF

15k

0.01μF

VOUT2

SD3

OFF ON

SD2

SD1

AIN

PGND1 SGND PGND2

56pF

1M

10k

309k

33pF

100k

110k

47μF

VOUT1

3.3V

500mA

1A FOR

VIN ≥ 3V

VOUT

1.5V

200mA

4.7μF

3520 TA01

Efficiency vs VIN

100

BUCK-BOOST

95

IOUT = 150mA

BUCK

90

IOUT = 250mA

85

80

75

70

2.2 2.7 3.2 3.7 4.2 4.7 5.2

VIN (V)

3520 TA01b

3520fa

1

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