SG1842(2000) データシートの表示（PDF） - Microsemi Corporation

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SG1842
(Rev.:2000)

CURRENT MODE PWM CONTROLLER

Microsemi Corporation 

PRODUCT DATABOOK 1996/1997

SG1842/SG1843 Series

CURRENT-MODE PWM CONTROLLER

PRODUCTION DATA SHEET

T Y P I C A L A P P L I C A T I O N C I R C U I T S (continued)

VCC

VIN

7 (12)

8 (14)

4 (7)

7 (11)

Q1

2 (3)

SG1842/43

6 (10)

I

1 (1)

R2

MPSA63

C

R1

5 (9)

5 (8)

3 (5)

VCS

RS

I

= VCS Where: V



= 1.67 

R1



 and V

= 1V (Typ.)

PK R

S

CS

 R1+R2 

C.S.MAX

tSOFTSTART = -ln



1



-

V - 1.3

EAO

5



R1

R1+R2















R1 R2

R1+R2







C

where; VEAO ≡ voltage at the Error Amp Output under

minimum line and maximum load conditions.

FIGURE 19. — ADJUSTABLE BUFFERED REDUCTION OF CLAMP LEVEL

WITH SOFTSTART

Softstart and adjustable peak current can be done with the external

circuitry shown above.

RA

6

RB

8

4

555

TIMER

2

1

f=

1.44

(RA + 2RB)C

f

=

RB

RA + 2RB

8 (14)

SG1842/43

3

4 (7)

To other

SGX842/43

5 (9)

FIGURE 20. — EXTERNAL DUTY CYCLE CLAMP AND

MULTI-UNIT SYNCHRONIZATION

Precision duty cycle limiting as well as synchronizing several 1842/

1843's is possible with the above circuitry.

2.8V

1.1V

SG1842/43

5V

8 (14)

RT

4 (7)

CT

Discharge

Current

Id = 8.2mA

2.5V

SG1842/43

2 (3)

Ri

1 (1)

RF

RF ³ 10K

0.5mA

FIGURE 21. — OSCILLATOR CONNECTION

The oscillator is programmed by the values selected for the timing

components RT and CT. Refer to application information for

calculation of the component values.

FIGURE 22. — ERROR AMPLIFIER CONNECTION

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

12

Copyright © 2000

Rev. 1.6 4/00

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