LTC3545/LTC3545-1

1

35451fb

TYPICAL APPLICATION

FEATURES

APPLICATIONS

DESCRIPTION

Triple 800mA Synchronous

Step-Down Regulator–2.25MHz

monolithic synchronous buck regulators using a constant

frequency, current mode architecture. The regulators op-

erate independently with separate run pins. The 2.25V to

5.5V input voltage range makes the LTC3545/LTC3545-1

well suited for single Li-Ion battery-powered applications.

Low ripple pulse skip mode or high efficiency Burst Mode

operation is externally selectable. PWM pulse skip mode

operation provides very low output ripple voltage while

Burst Mode operation increases efficiency at low output

loads.

Switching frequency is internally set to 2.25MHz, or the

switching frequency can be synchronized to an external

1MHz to 3MHz clock. Power good indicators easily allow

power on sequencing between the three regulators.

The internal synchronous switches increase efficiency and

eliminate external Schottky diodes. Low output voltages are

supported with the 0.6V feedback reference voltage.

The LTC3545-1 replaces the SYNC/MODE function with a

third PGOOD pin and forces Burst Mode operation.

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Three 800mA Outputs

■

High Efficiency: Up to 95%

■

2.25V to 5.5V Input Voltage Range

■

■

2.25MHz Constant Frequency Operation or

■

Synchronizable to External 1MHz to 3MHz Clock

■

Power Good Indicators Ease Supply Sequencing

■

0.6V Reference Allows Low Output Voltages

■

Current Mode Operation/Excellent Transient Response

■

Low Profile 16-Lead 3mm

× 3mm QFN Package

■

Smart Phones

■

Wireless and DSL Modems

■

Digital Still Cameras

■

Portable Instruments

■

Point of Load Regulation

High Efficiency Triple Step-Down Converter with Power Sequencing

Efficiency and Loss vs Load Current

L, LT, LTC, 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 6580258, 5481178, 6127815, 6498466, 6611131.

3545 TA01

L1

1.5μH

C5

10μF

PGND

GNDA

C4 10μF

C6

20pF

R2

255k

R1

511k

C1

10μF

1.8V

2.25V TO 5.5V

RUN1

PGOOD1

RUN2

PGOOD2

RUN3

L2

1.5μH

R4

226k

C2

10μF

1.2V

SW2

SYNC/MODE

SW1

LTC3545

GNDA

PGND

R7

500k

C7

20pF

R3

226k

R8

500k

L3

1.5μH

R6

200k

C3

10μF

1.5V

SW3

C8

20pF

R5

301k

LOAD CURRENT (A)

30

90

100

20

10

80

50

70

60

40

0.0001

0.01

0.1

1

3545 TA01b

0

0.001

1

0.1

0.01

0.0001

0.001

Burst Mode OPERATION

SINGLE CHANNEL