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LT1777

TYPICAL APPLICATIONS

Basic 5V Output Application

Figure 8 shows a basic application that produces 5V at up

to 500mA IOUT. Efficiency and Internal Power Dissipation

graphs are shown in Figure 9 for input voltages of 12V,

24V and 36V, and for sense inductor values of 0

µH, 1µH

and 2.2

µH. Be aware that continuous operation at the

combination of high input voltage, large sense inductor

and high output current may not be possible due to

thermal constraints. (Brief transients in input voltage or

output current should not present a problem, though.) As

shown, the SHDN and SYNC pins are unused, however

either (or both) can be optionally driven by external signals

as desired.

The data as shown were performed using an off-the-shelf

Coilcraft DO3316-224 as the main inductor. This is a

cost-effective inductor using an open style of construc-

tion. For a toroidal style inductor, the Coiltronics

CTX250-4 or similar may be substituted.

VIN

VCC

VSW

LT1777

SHDN

SYNC

µH TO 2.2µH

(SEE BELOW)

220

µH

100

µF

10V

36.5k

1777 F08

VOUT

12.1k

VIN

10V TO 40V

SGND

µF

63V

12k

2200pF

100pF

C1: PANASONIC HFQ ELECTROLYTIC

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. GRAPHICAL DATA TAKEN WITH:

µH = D01608C-102, COILCRAFT OR SIMILAR

2.2

µH = D01608C-222, COILCRAFT OR SIMILAR (SEE TEXT)

L2: COILCRAFT D03316-224 OR SIMILAR (SEE TEXT)

100pF

0.1

µF

0.1

µF

Figure 8. Basic 5V Output Application

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