LTC1772HS6 データシートの表示（PDF） - Linear Technology

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LTC1772HS6

Constant Frequency Current Mode Step-Down DC/DC Controller in SOT-23

Linear Technology 

LTC1772

Constant Frequency

Current Mode Step-Down

DC/DC Controller in SOT-23

FEATURES

■ High Efficiency: Up to 94%

■ High Output Currents Easily Achieved

■ Wide VIN Range: 2.5V to 9.8V

■ Constant Frequency 550kHz Operation

■ Burst Mode® Operation at Light Load

■ Low Dropout: 100% Duty Cycle

■ Tiny 6-Lead SOT-23 Package

■ 0.8V Reference Allows Low Output Voltages

■ Current Mode Operation for Excellent Line and Load

Transient Response

■ Low Quiescent Current: 270µA

■ Shutdown Mode Draws Only 8µA Supply Current

■ ±2.5% Reference Accuracy

U

APPLICATIO S

■ One or Two Lithium-Ion-Powered Applications

■ Cellular Telephones

■ Wireless Modems

■ Portable Computers

■ Distributed 3.3V, 2.5V or 1.8V Power Systems

■ Scanners

DESCRIPTIO

The LTC®1772 is a constant frequency current mode step-

down DC/DC controller providing excellent AC and DC load

and line regulation. The device incorporates an accurate

undervoltage lockout feature that shuts down the LTC1772

when the input voltage falls below 2.0V.

The LTC1772 provides a ±2.5% output voltage accuracy

and consumes only 270µA of quiescent current. For

applications where efficiency is a prime consideration, the

LTC1772 is configured for Burst Mode operation, which

enhances efficiency at low output current.

To further maximize the life of a battery source, the

external P-channel MOSFET is turned on continuously in

dropout (100%dutycycle).In shutdown, the device draws

a mere 8µA. High constant operating frequency of 550kHz

allows the use of a small external inductor.

The LTC1772 is available in a small footprint 6-lead

SOT-23.

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

Burst Mode is a registered trademark of Linear Technology Corporation.

All other trademarks are the property of their respective owners.

TYPICAL APPLICATIO

10k

220pF

1

6

ITH/RUN PGATE

LTC1772

2

GND

3

VFB

5

VIN

SENSE– 4

R1

0.03Ω

L1

M1 4.7µH

+

D1

C1

10µF

10V

C2A

47µF

6V

VIN

2.5V

TO 9.8V

VOUT

2.5V

C2B

2A

1µF

10V 174k

C1: TAIYO YUDEN LMK325BJ106K-T

C2A: SANYO 6TPA47M

C2B: AVX 0805ZC105KAT1A

D1: MOTOROLA MBRM120T3

L1: MURATA LQN6C-4R7

M1: FAIRCHILD FDC638P

R1: IRC LRC-LR1206-01-R030F

80.6k

1772 F01a

Figure 1. High Efficiency, High Output Current 2.5V/2A Regulator

Efficiency vs Load Current

100

VIN = 3.3V VIN = 4.2V

90

80

VIN = 6V

70

VIN = 9.8V VIN = 8.4V

60

50

40

1

VOUT = 2.5V

10

100

1000

LOAD CURRENT (mA)

10000

1772 F01b

1772fb

1

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