LT1776I View Datasheet(PDF) - Linear Technology

Part Name

Description

Manufacturer

LT1776I

Wide Input Range, High Efficiency, Step-Down Switching Regulator

Linear Technology 

LT1776

TYPICAL APPLICATIONS

Minimum Component Count Application

Figure 4a shows a basic “minimum component count”

application. The circuit produces 5V at up to 500mA IOUT

with input voltages in the range of 10V to 40V. The typical

POUT/PIN efficiency is shown in Figure 4b. As shown, the

SHDN and SYNC pins are unused, however either (or both)

can be optionally driven by external signals as desired.

User-Programmable Undervoltage Lockout

Figure 5 adds a resistor divider to the basic application.

This is a simple, cost-effective way to add a user-

programmable undervoltage lockout (UVLO) function.

Resistor R5 is chosen to have approximately 200µA

through it at the nominal SHDN pin lockout threshold of

1.25V. The somewhat arbitrary value of 200µA was

VIN

10V TO

40V

+ C1

39µF

63V

5

1

VIN

2

SHDN VCC

3

VSW

C5

100pF

LT1776

6

SYNC

7

FB

8

VC

GND

4

D1

L1 +

MBRS1100 100µH

C2

100µF

10V

C3

2200pF

X7R

R3

22k

5%

C4

100pF

C1: PANASONIC HFQ

C2: AVX D CASE TPSD107M010R0080

C4, C5: X7R OR COG/NPO

D1: MOTOROLA 100V, 1A, SMD SCHOTTKY

L1: COILCRAFT DO3316P-104

FOR 3.3V VOUT VERSION:

R1: 24.3K, R2: 14.7k

L1: 68µH, DO3316P-683

IOUT: 0mA TO 500mA

R1

36.5k

1%

VOUT

5V

0mA to 500mA

R2

12.1k

1%

1776 F04a

Figure 4a. Minimum Component Count Application

90

80

70

60

50

40

VIN = 10V

30 VIN = 20V

VIN = 30V

20

1

VIN = 40V

10

100

ILOAD (mA)

1000

1776 F04b

Figure 4b. POUT/PIN Efficiency

14

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