13

FN7296.2

May 13, 2005

The second way of offset tracking is to use the EN and

Power Good pins, as shown in Figure 25. In this

3. External Soft Start

An external soft start can be combined with auxiliary supply

tracking to provide desired soft start other than internally

preset soft start (Figure 26). The appropriate start-up time is:

t

s

RC

V

O

V

IN

---------

×

×

=

FIGURE 25. OFFSET TRACKING

2

3

16

15

14

13

5

6

7

12

11

9

8

10

19

18

EL7563

2

3

16

15

14

13

5

6

7

12

11

9

8

10

19

18

EL7563

1

20

1

20

EN

PG

EN

PG

TIME

FIGURE 26. EXTERNAL SOFT START

1

2

15

14

13

12

6

7

8

11

10

9

20

19

EL7563

-

+

STP

STN

R

C

EL7563