SG1844/SG1845 Series

PRODUCT DA T ABOOK 1996/1997

Copyright © 2000

Rev. 1.4

4/00

12

TYPICAL APPLICA TION CIRCUITS

(continued)

FIGURE 19. — EXTERNAL DUTY CYCLE CLAMP AND

MULTI-UNIT SYNCHRONIZATION

FIGURE 18. — ADJUSTABLE BUFFERED REDUCTION OF CLAMP LEVEL

WITH SOFTSTART

Precision duty cycle limiting for a duty cycle of <50%, as well as

synchronizing several 1844/45's is possible with the above circuitry.

Softstart and adjustable peak current can be done with the external

circuitry shown above.

I

Where: 0

≤ V

t

C

7 (12)

6 (10)

7 (11)

5 (8)

3 (5)

SG1844/45

V

CC

V

IN

Q1

R

S

5 (9)

8 (14)

4 (7)

2 (3)

1 (1)

2N2907

R

2

R

1

C

2

6

R

B

R

A

1

84

3

555

TIMER

4 (7)

5 (9)

8 (14)

SG1844/45

To other

SG1844/45

C

FIGURE 21. — ERROR AMPLIFIER CONNECTION

FIGURE 20. — OSCILLATOR CONNECTION

7 (11)

6 (10)

5V

C

T

2.8V

1.1V

SG1844/45

Discharge

Current

I

R

T

1 (1)

R

F

R

i

2 (3)

R

2.5V

SG1844/45

0.5mA

The oscillator is programmed by the values selected for the timing

components R

Refer to application information for

calculation of the component values.

Error amplifier is capable of sourcing and sinking current up to 0.5mA.

f =

(R

1.44

f =

R

R

B

V

1

R

S

R

R

1.43 - 0.23

1+













V

C

V

2

and V

where: V

R

1

R

2

R

1

R

2

0.5

1+

R

1

R

2