TL497A

SWITCHING VOLTAGE REGULATORS

SLVS009D – JUNE 1976 – REVISED JULY 1999

5

POST OFFICE BOX 655303

APPLICATION INFORMATION

VI

L

14

13

10

8

7

6

5

4

3

2

1

TL497A

R2 = 1.2 k

Ω

R1

VO

CO

BASIC CONFIGURATION

(Peak Switching Current = I(PK) < 500 mA)

VI

RCL

L

R1

8

10

13

14

12

3

4

5

EXTENDED POWER CONFIGURATION

(using external transistor)

TL497A

DESIGN EQUATIONS

I

(PK) +

2I

O

max

V

O

V

I

L(

mH) +

V

I

I

(PK)

ton (ms)

C

T

(pF)

[ 12 ton (ms)

R1

+ (V

O

–1.2 V) k

W

Choose L (50 to 500

µH), calculate

ton (25 to 150 µs)

R

CL +

0.5 V

I

(PK)

C

O

(

mF) [ ton(ms)

V

I

V

O

I

(PK) )

I

O

V

ripple

(PK)

CT

R2 = 1.2 k

Ω

VO

CO

CT

RCL

Figure 1. Positive Regulator, Step-Up Configurations