LT3685E 查看數據表（PDF） - Linear Technology

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LT3685E

36V, 2A, 2.4MHz Step-Down Switching Regulator

Linear Technology 

LT3685

36V, 2A, 2.4MHz Step-Down

Switching Regulator

FEATURES

■ Wide Input Range:

Operation From 3.6V to 36V

Overvoltage Lockout Protects Circuit through

60V Transients

■ 2A Maximum Output Current

■ Adjustable Switching Frequency: 200kHz to 2.4MHz

■ Low Shutdown Current: IQ < 1μA

■ Integrated Boost Diode

■ Synchronizable Between 250kHz to 2MHz

■ Power Good Flag

■ Saturating Switch Design: 0.25 On-Resistance

■ 0.790V Feedback Reference Voltage

■ Output Voltage: 0.79V to 20V

■ Soft-Start Capability

■ Small 10-Pin Thermally Enhanced MSOP and

(3mm × 3mm) DFN Packages

APPLICATIONS

■ Automotive Battery Regulation

■ Set Top Box

■ Distributed Supply Regulation

■ Industrial Supplies

■ Wall Transformer Regulation

DESCRIPTION

The LT®3685 is an adjustable frequency (200kHz to 2.4MHz)

monolithic step-down switching regulator that accepts

input voltages up to 38V operating and 60V maximum. An

internal overvoltage protection circuit turns off the power

switch when VIN is above 38V typical (36V minimum) which

then allows the part to safely withstand 60V transients. A

high efficiency 0.25 switch is included on the die along

with a boost Schottky diode and the necessary oscillator,

control, and logic circuitry. Current mode topology is

used for fast transient response and good loop stability.

The LT3685’s high operating frequency allows the use of

small, low cost inductors and ceramic capacitors result-

ing in low output ripple while keeping total solution size

to a minimum. The low current shutdown mode 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 89% of the programmed output voltage. The

LT3685 is available in 10-Pin MSOP and 3mm × 3mm DFN

packages 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 APPLICATION

3.3V Step-Down Converter

VIN

4.5V TO 36V

TRANSIENT

TO 60V

OFF ON

14k

4.7μF

470pF

40.2k

VIN

RUN/SS

BD

BOOST

VC

LT3685

SW

RT

PG

SYNC

GND

FB

VOUT

3.3V

2A

0.47μF 4.7μH

316k

100k

22μF

3685 TA01

Efficiency

100

VOUT = 5V

90

80

VOUT = 3.3V

70

60

VIN = 12V

L = 5.6μH

50

F = 800 kHz

0 0.5

1.0

1.5

2

LOAD CURRENT (A)

3685 TA01b

3685fb

1

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