LT3973/LT3973-3.3/LT3973-5

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3973fb

For more information www.linear.com/LT3973

TYPICAL APPLICATION

DESCRIPTION

42V, 750mA Step-Down

Regulator with 2.5µA

Quiescent Current and

Integrated Diodes

The LT®3973 is an adjustable frequency monolithic buck

switchingregulatorthatacceptsawideinputvoltagerange

up to 42V, and consumes only 2.5µA of quiescent current.

A high efficiency switch is included on the die along with

the catch diode, boost diode, and the necessary oscillator,

controlandlogiccircuitry.LowrippleBurstModeoperation

maintainshighefficiencyatlowoutputcurrentswhilekeep-

ing the output ripple below 10mV in a typical application.

A minimum dropout voltage of 530mV is maintained when

theinputvoltagedropsbelowtheprogrammedoutputvolt-

age, such as during automotive cold crank. Current mode

topology is used for fast transient response and good loop

stability. A catch diode current limit provides protection

against shorted outputs and overvoltage conditions, with

thermalshutdownprovidingadditionalfaultprotection.An

accurate programmable undervoltage lockout feature is

available, producing a low shutdown current of 0.75µA.

the programmed output voltage. The LT3973 is available

in small, thermally enhanced 10-lead MSOP and 3mm ×

3mm DFN packages.

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.

5V Step-Down Converter

FEATURES

APPLICATIONS

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Ultralow Quiescent Current

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Wide Input Voltage Range: 4.2V to 42V Operating

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Adjustable Switching Frequency: 200kHz to 2.2MHz

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Integrated Boost and Catch Diodes

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750mA Output Current

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Excellent Start-Up and Dropout Performance

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Fixed Output Voltages: 3.3V, 5V

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Accurate Programmable Undervoltage Lockout

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Internal Catch Diode Current Limit

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Power Good Flag

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Thermal Shutdown

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Small, Thermally Enhanced 10-Lead MSOP and

(3mm × 3mm) DFN Packages

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Automotive Battery Regulation

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Power for Portable Products

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Industrial Supplies

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Gate Drive Bias

BOOST

LT3973

SW

EN/UVLO

PG

RT

C3

0.47µF

15pF

C2

22µF

C1

4.7µF

5.6V TO 42V

5V

750mA

1M

316k

215k

f = 600kHz

L1

15µH

BD

OUT

FB

GND

OFF ON

3973 TA01a

Efficiency

LOAD CURRENT (mA)

0.01

40

80

70

60

50

90

100

0.1

1

3973 TA01b

10

0.01

10

100

1

0.1

1000