LT3681 Просмотр технического описания (PDF) - Linear Technology

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LT3681

36V, 2A, 2.8MHz Step-Down Switching Regulator with Integrated Power Schottky Diode

Linear Technology 

LT3681

36V, 2A, 2.8MHz Step-Down

Switching Regulator with

Integrated Power Schottky Diode

FEATURES

■ Wide Input Voltage Range: 3.6V to 34V Operating,

36V Maximum

■ 2A Maximum Output Current

■ Low Ripple Burst Mode® Operation

50µA IQ at 12VIN to 3.3VOUT

Output Ripple < 15mVP-P

■ Adjustable Switching Frequency: 300kHz to 2.8MHz

■ Low Shutdown Current: IQ < 1µA

■ Integrated Boost Diode

■ Integrated Power Schottky Diode

■ Power Good Flag

■ Saturating Switch Design: 0.18Ω On-Resistance

■ 1.265V Feedback Reference Voltage

■ Output Voltage: 1.265V to 20V

■ Soft-Start Capability

■ Small 14-Pin Thermally Enhanced

(4mm x 3mm) DFN Package

U

APPLICATIO S

■ Automotive Battery Regulation

■ Power for Portable Products

■ Distributed Supply Regulation

■ Industrial Supplies

■ Wall Transformer Regulation

DESCRIPTIO

The LT®3681 is an adjustable frequency (300kHz to 2.8MHz)

monolithic buck switching regulator that accepts input

voltages up to 34V (36V maximum). A high efficiency

0.18Ω switch is included on the die along with a boost

Schottky diode and the necessary oscillator, control, and

logic circuitry. An undedicated power Schottky diode is

integrated into the LT3681 to minimize the solution size.

Current mode topology is used for fast transient response

and good loop stability. Low ripple Burst Mode operation

maintains high efficiency at low output currents while

keeping output ripple below 15mV in a typical application.

In addition, the LT3681 can further enhance low output

current efficiency by drawing bias current from the output

when VOUT is above 3V. Shutdown reduces input supply

current to less than 1µA while a resistor and capacitor on

the RUN/SS pin provide a controlled output voltage ramp

(soft-start). A power good flag signals when VOUT reaches

90% of the programmed output voltage. The LT3681

is available in 14-Pin 4mm x 3mm DFN package with

exposed pads for low thermal resistance.

, LT, LTC and LTM 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

5V Step-Down Converter

VIN

6.3V TO

34V

4.7mF

OFF ON

20k

330pF

60.4k

VIN

RUN/SS

BD

BOOST

VC LT3681

SW

DC

RT

DA

PG

BIAS

GND

FB

0.47mF L

6.8mH

VOUT

5V

2A

590k

200k

22mF

L: NEC PLC-0745-6R8

3681 TA01

Efficiency

100

90

80

70

60

50

40

30

20

10

0

0.0001 0.001

10.0000

1.0000

0.1000

0.0100

0.01 0.1

ILOAD (A)

VIN = 12V

VOUT = 3.3V

L = 4.7mH

0.0010

F = 800 kHz

0.0001

1

10

3681 TA01b

3681f

1

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