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LTC1874

FEATURES

APPLICATIO S

DESCRIPTIO

Dual Constant Frequency

Current Mode Step-Down

DC/DC Controller

The LTC

step-down DC/DC controller with excellent AC and DC load

and line regulation. Each controller has an accurate

undervoltage lockout that shuts down the individual con-

troller when the input voltage falls below 2.0V.

The LTC1874 boasts

±2.5% output voltage accuracy and

consumes only 270

µA of quiescent current per controller.

The LTC1874 is configured with Burst Mode operation,

which enhances efficiency at low output current for appli-

cations where efficiency is a prime consideration.

To further maximize the life of a battery source, each

external P-channel MOSFET is turned on continuously in

dropout (100% duty cycle). In shutdown, each controller

draws a mere 8

µA. High constant operating frequency of

550kHz allows the use of small external inductors.

The LTC1874 is available in a small footprint 16-lead

narrow SSOP.

Figure 1. LTC1874 3.5V-9.5V Input to 3.3V/1A and 1.8V/1A Dual Step-Down Converter

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1- or 2-Cell Lithium-Ion-Powered Applications

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Personal Information Appliances

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Portable Computers

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Distributed 3.3V, 2.5V or 1.8V Power Systems

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High Efficiency: Up to 94%

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High Output Currents Easily Achieved

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Constant Frequency 550kHz Operation

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Burst Mode

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Low Dropout: 100% Duty Cycle

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0.8V Reference Allows Low Output Voltages

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Current Mode Operation for Excellent

Line and Load Transient Response

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Low Quiescent Current: 270

µA (Each Controller)

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Separate Shutdown Pin for Each Controller

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Shutdown Mode Draws Only

8

µA Supply Current (Each Controller)

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±2.5% Reference Accuracy

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Available in 16-Lead Narrow SSOP

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Each Controller Functions Independent of the Other

, LTC and LT are registered trademarks of Linear Technology Corporation.

Burst Mode is a trademark of Linear Technology Corporation.

GND1

PGND1

PGATE1

8

7

6

5

12

11

10

9

1

2

3

4

13

14

15

16

PGATE2

PGND2

GND2

LTC1874

10k

220pF

M2

D2

C2

47

µF

6V

R2

0.04

Ω

L2

4.7

µH

220pF

10k

R1

0.04

Ω

80.6k

1874 TA01

100k

1.8V

1A

+

80.6k

249k

C1

47

µF

6V

C1, C2: SANYO POSCAP 6TPA47M

EMK325BJ106MNT (

×2)

D1, D2: MBRM120

L1, L2: COILCRAFT D01608C-472

M1, M2: Si3443DV

R1, R2: DALE 0.25W

L1

4.7

µH

+

10

µF

16V

×2

3.5V

TO 9.5V

D1

M1

3.3V

1A