13

LT1111

1111fd

S

APPLICATI

I FOR ATIO

Table 2. Inductor Manufacturers

MANUFACTURER

PART NUMBERS

Coiltronics Incorporated

CTX100-4 Series

6000 Park of Commerce Blvd.

Surface Mount

Boca Raton, FL 33487

407-241-7876

Toko America Incorporated

Type 8RBS

1250 Feehanville Drive

Mount Prospect, IL 60056

312-297-0070

Sumida Electric Co. USA

CD54

708-956-0666

CDR74

CDR105

Surface Mount

Using the Gain Block

The gain block (GB) on the LT1111 can be used as an error

amplifier, low-battery detector or linear post regulator.

The gain block itself is a very simple PNP input op amp with

an open collector NPN output. The negative input of the

gain block is tied internally to the 1.25V reference. The

positive input comes out on the SET pin.

Arrangement of the gain block as a low-battery detector

is straightforward. Figure 12 shows hookup. R1 and R2

need only be low enough in value so that the bias current

of the SET input does not cause large errors. 33k for R2

is adequate. R3 can be added to introduce a small amount

of hysteresis. This will cause the gain block to “snap”

when the trip point is reached. Values in the 1M to 10M

range are optimal. However, the addition of R3 will

change the trip point.

Table 3. Capacitor Manufacturers

MANUFACTURER

PART NUMBERS

Sanyo Video Components

OS-CON Series

1201 Sanyo Avenue

San Diego, CA 92073

619-661-6322

Nichicon America Corporation

PL Series

927 East State Parkway

Schaumberg, IL 60173

708-843-7500

Sprague Electric Company

150D Solid Tantalums

Lower Main Street

550D Tantalex

Sanford, ME 04073

207-324-4140

Matsuo

267 Series

714-969-2491

Surface Mount

LT1111 • F12

R1

R2

1.25V

REF

SET

GND

IN

V

LT1111

47k

5V

TO

PROCESSOR

+

–

A0

R3

R1 =

35.1

µA

R2 = 33k

R3 = 1.6M

Figure 12. Setting Low-Battery Detector Trip Point

Table 1. Component Selection for Common Converters

INPUT

OUTPUT

OUTPUT

CIRCUIT

INDUCTOR

INDUCTOR

CAPACITOR

VOLTAGE

VOLTAGE

CURRENT (MIN)

FIGURE

VALUE

PART NUMBER

VALUE

NOTES

2 to 3.1

5

90mA

4

15

µH

S CD75-750K

33

µF*

2 to 3.1

5

10mA

4

47

µH

S CD54-470K, C CTX50-1

10

µF

2 to 3.1

12

30mA

4

15

µH

S CD75-150K

22

µF

2 to 3.1

12

10mA

4

47

µH

S CD54-470K, C CTX50-1

10

µF

5

12

90mA

4

33

µH

S CD75-330K

22

µF

5

12

30mA

4

47

µH

S CD75-470K, C CTX50-1

15

µF

6.5 to 11

5

50mA

5

15

µH

S CD54-150K

47

µF**

12 to 20

5

300mA

5

56

µH

S CD105-560K, C CTX50-4

47

µF**

20 to 30

5

300mA

5

120

µH

S CD105-121K, C CTX100-4

47

µF**

5

–5

75mA

6

56

µH

S CD75-560K, C CTX50-4

47

µF

12

–5

250mA

6

120

µH

S CD105-121K, C CTX100-4

100

µF**

S = Sumida

C = Coiltronics

* Add 47

** Add 220