LT3845EFEPBF 查看數據表（PDF） - Linear Technology

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LT3845EFEPBF

High Voltage Synchronous Current Mode Step-Down Controller with Adjustable Operating Frequency

Linear Technology 

FEATURES

■ High Voltage Operation: Up to 60V

■ Synchronizable Up to 600kHz

■ Adjustable Constant Frequency: 100kHz to 500kHz

■ Output Voltages Up to 36V

■ Adaptive Nonoverlap Circuitry Prevents Switch

Shoot-Through

■ Reverse Inductor Current Inhibit for Discontinuous

Operation Improves Efficiency with Light Loads

■ Programmable Soft-Start

■ 120μA No Load Quiescent Current

■ 10μA Shutdown Supply Current

■ 1% Regulation Accuracy

■ Standard Gate N-Channel Power MOSFETs

■ Current Limit Unaffected by Duty Cycle

■ Reverse Overcurrent Protection

■ 16-Lead Thermally Enhanced TSSOP Package,

16-Pin PDIP

APPLICATIONS

■ 12V and 42V Automotive and Heavy Equipment

■ 48V Telecom Power Supplies

■ Avionics and Industrial Control Systems

■ Distributed Power Converters

LT3845

High Voltage Synchronous

Current Mode Step-Down

Controller with Adjustable

Operating Frequency

DESCRIPTION

The LT®3845 is a high voltage, synchronous, current

mode controller used for medium to high power, high

efficiency supplies. It offers a wide 4V to 60V input range

(7.5V minimum start-up voltage). An onboard regulator

simplifies the biasing requirements by providing IC power

directly from VIN.

Burst Mode® operation maintains high efficiency at light

loads by reducing IC quiescent current to 120μA. Light

load efficiency is also improved with the reverse inductor

current inhibit function which supports discontinuous

operation.

Additional features include adjustable fixed operating

frequency that can be synchronized to an external clock

for noise sensitive applications, gate drivers capable of

driving large N-channel MOSFETs, a precision undervoltage

lockout, 10μA shutdown current, short-circuit protection

and a programmable soft-start.

The LT3845 is available in a 16-lead thermally enhanced

TSSOP package and 16-pin through hole N package.

L, LT, LTC, LTM, Burst Mode, Linear Technology and the Linear logo are registered trademarks

of Linear Technology Corporation. All other trademarks are the property of their respective

owners.. Protected by U.S. Patents, including 5481178, 6611131, 6304066, 6498466, 6580258.

TYPICAL APPLICATION

High Voltage Step-Down Regulator 48V to 12V at 75W

VIN

20V TO 55V

2.2μF

100V

47μF

63V

82.5k

1M

1500pF

VIN

BOOST

SHDN

TG

LT3845

CSS

SW

BURST_EN

VCC

16.2k

143k

20k

2200pF

100pF

49.9k

VFB

VC

SYNC

fSET

BG

PGND

SENSE+

SENSE–

SGND

0.1μF

BAS521

Si7370DP

Si7370DP

15μH

B160

0.01Ω

VOUT

12V

75W

33μF

×3

1μF

1N4148

3845 TA01a

Efficiency and Power Loss vs

Load Current

100

7

VIN = 48V

95

6

90

5

85

4

80

3

75

2

LOSS

70

1

65

0.1

1

LOAD CURENT (A)

0

10

3845 TA01b

3845fd

1

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