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LT1777

©LINEAR TECHNOLOGY CORPORATION 1999

1777f LT/TP 0899 4K • PRINTED IN USA

Linear Technology Corporation

1630 McCarthy Blvd., Milpitas, CA 95035-7417

circuit is capable of delivering up to 300mA at 5V, from

input voltages as high as 28V. The only disadvantage is

that due to the increased resistance in the inductor, the

circuit is no longer capable of withstanding indefinite short

circuits to ground. The LT1777 will still current limit at its

Momentary short circuits of a few seconds or less can still

be tolerated.

Minimum PC Board Size Application

The previously described basic applications employ power

path parts which are capable of delivering the full rated

input supply voltage and output current capabilities of the

LT1777. A substantial improvement in printed circuit

board area requirements can be achieved with the circuit

shown below. This uses a physically smaller and less

costly power inductor and a tantalum input capacitor. This

PART NUMBER

DESCRIPTION

COMMENTS

LT1076

100kHz, 2A Step-Down Switching Regulator

LT1533

Ultralow Noise 1A Switching Regulator

Push-Pull Design for Low Noise Isolated Supplies

LT1534

Ultralow Noise 2A Switching Regulator

Ultralow Noise Regulator for Boost Topologies

LT1576

200kHz, 1.5A Step-Down Switching Regulator

Output Up to 1.25A, Integrated Switch, SO-8 Package

LTC1622

Fixed Frequency 550kHz Operation, MSOP Package

LTC1624

High Efficiency SO-8 DC/DC Controller

LT1676/LT1776

Wide Input Range, High Efficiency, Step-Down Voltage Regulator 7.4V to 60V Input, 100/200kHz Operation, 700mA Internal Switch

RELATED PARTS

+

LT1777

SHDN

SYNC

4

10

7

6

D1

L1

0

µH TO 2.2µH

(SEE BELOW)

L2

200

µH

C2

100

µF

10V

R1

36.5k

1%

1777 TA03

5V

R2

12.1k

1%

5

3

10V TO 28V

12

14

13

FB

SGND

+

C1

22

µF

35V

R3

12k

C3

2200pF

C4

100pF

C1: AVX E CASE TPSE226M035R0300

C2: AVX D CASE TPSD107M010R0080

C3, C4, C5: NPO OR X7R

C6, C7: Z5U

D1: MOTOROLA 100V, 1A SMD SCHOTTKY

MBRS1100

L1: SENSE INDUCTOR CAN VARY FROM 0

µH TO 2.2µH

AS PER APPLICATION. SEE PREVIOUS SCHEMATICS

FOR EXAMPLES

L2: COILCRAFT CTX200-1 OR SIMILAR

C5

100pF

C6

0.1

µF

C7

0.1

µF

Minimum PC Board Area Application