LTC3805

1

3805fb

TYPICAL APPLICATION

FEATURES

APPLICATIONS

DESCRIPTION

Adjustable Frequency

Current Mode Flyback

DC/DC Controller

DC/DC converters designed to drive an N-channel MOSFET

in high input and output voltage converter applications.

Operating frequency and slope compensation can be pro-

grammed by external resistors. Programmable overcurrent

sensing protects the converter from short-circuits. Soft-

start can be programmed using an external capacitor

and the soft-start capacitor also programs an automatic

restart feature.

The LTC3805 provides ±1.5% output voltage accuracy

and consumes only 360μA of quiescent current during

normal operation and only 40μA during micropower start-

up. Using a 9.5V internal shunt regulator, the LTC3805 can

be powered directly from a low impedance DC voltage of

9V or less.

The LTC3805 is available in the 10-lead MSOP package

and the 3mm × 3mm DFN package.

36V – 72V to 5V/2A Nonisolated Flyback Converter

■

■

Adjustable Slope Compensation

■

Adjustable Overcurrent Protection with Automatic

Restart

■

Adjustable Operating Frequency (70kHz to 700kHz)

with One External Resistor

■

Synchronizable to an External Clock

■

±1.5% Reference Accuracy

■

Current Mode Operation for Excellent Line and Load

Transient Response

■

RUN Pin with Precision Threshold and Adjustable

Hysteresis

■

Programmable Soft-Start with One External Capacitor

■

Low Quiescent Current: 360μA

■

Small 10-Lead MSOP and 3mm × 3mm DFN

■

Telecom Power Supplies

■

42V and 12V Automotive Power Supplies

■

Isolated Electronic Equipment

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

All other trademarks are the property of their respective owners.

LTC3805

GND

RUN

GATE

OC

SSFLT

FS

FB

118k

3k

68mΩ

22μF

× 2

22μF

SYNC

1.33k

8.66k

221k

100k

36V TO

72V

5V

AT 2A

13.7k

71.5k

100μF

× 2

3805 TA01a

0.1μF

20k

470pF

LOAD CURRENT (A)

0.01

0

20

30

40

50

60

70

0.1

1

3805 TA01b

80

90

100

10

1

0.1

10

10

LOSS

EFFICIENCY

Efficiency and Power Loss