LTC3644/LTC3644-2

1

Rev. 0

For more information www.analog.com

TYPICAL APPLICATION

FEATURES

DESCRIPTION

Quad 17V, 1.25A Parallelable Synchronous Step-

Down Regulator with Ultralow Quiescent Current

The LTC®3644/LTC3644-2 is a quad 1.25A output, high

efficiencysynchronousmonolithicstep-downregulatorcapable

of operating from input supplies up to 17V. The switching

frequency is internally fixed to 1MHz or 2.25MHz with a ±50%

synchronizationrange.Theregulatorfeaturesultralowquiescent

The step-down regulator operates from an input voltage

range of 2.7V to 17V and provides an adjustable output

output current per channel. LTC3644/LTC3644-2 can be

configuredforquad1.25Aoutputs,triple2.5A/1.25A/1.25A

outputs, dual 2.5A outputs, or dual 3.75A/1.25A outputs. A

user selectable mode input is provided to allow the user to

operationprovidesthehighestefficiencyatlightloads,while

forced-continuous mode provides the lowest ripple noise.

The regulators can be synchronized to an external clock.

LTC3644 Options

PART NAME

FREQUENCY

LTC3644

1.00MHz

Adjustable

LTC3644-2

2.25MHz

Adjustable

4-Channel 1.25A Quad-Output 1MHz Step-Down Regulator

APPLICATIONS

n

Quad Step-down Outputs: 1.25A per Channel

n

n

n

One Inductor

n

Integrated 300mΩ P-Channel/80mΩ N-Channel

MOSFETs Provide Up to 93% Efficiency

n

Channels Enabled

n

Constant Frequency (1MHz/2.25MHz) with ±50%

Frequency Synchronization Range

n

±1% Output Voltage Accuracy

n

Current Mode Operation for Excellent Line and Load

Transient Response

n

Full Dropout Operation (100% Duty Cycle)

n

Phase Shift Programmable with External Clock

n

5mm × 5mm × 1.72mm BGA Package

n

Battery Powered Systems

n

Point-of-Load Supplies

n

Portable – Handheld Scanners and Cameras

All registered trademarks and trademarks are the property of their respective owners. Protected

by U.S. patents, including 5481178, 6580258, 6498466, 6611131, 5705919.

Efficiency and Power Loss vs Load

at 1MHz in Burst Mode Operation

EFFICIENCY

POWER LOSS

LOAD CURRENT (A)

0.00

0.25

0.50

0.75

1.00

1.25

0

10

20

30

40

50

60

70

80

90

100

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

3644 TA01b

22pF

22pF

R1

619k

R2

196k

L1

3.3µH

47µF

47µF

4.7µF

22pF

22pF

R5

619k

R6

309k

L3

3.3µH

47µF

R3

619k

R4

137k

L2

4.7µH

R7

619k

R8

84.5k

L4

6.8µH

47µF

22µF

×4

RUN1

RUN2

RUN3

RUN4

PGOOD1

PGOOD2

PGOOD3

PGOOD4

MODE/SYNC

PHASE

SW1

FB1

SW3

FB3

2.5V AT 1.25A

1.8V AT 1.25A

5V AT 1.25A

3.3V AT 1.25A

SW2

FB2

SW4

FB4

GND

5V TO 17V

LTC3644

3644 TA01a

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