SG3843DM Microsemi Analog Mixed Signal Group, SG3843DM Datasheet - Page 12

• Manufacturer Part Number: SG3843DM
• Description: IC PWM CURRENT MODE 8SOIC
• Manufacturer: Microsemi Analog Mixed Signal Group

Specifications of SG3843DM

• Pwm Type: Current Mode
• Number Of Outputs: 1
• Frequency - Max: 500kHz
• Duty Cycle: 100%
• Voltage - Supply: 8.2 V ~ 30 V
• Buck: No
• Boost: No
• Flyback: Yes
• Inverting: No
• Doubler: No
• Divider: No
• Cuk: No
• Isolated: Yes
• Operating Temperature: 0°C ~ 70°C
• Package / Case: 8-SOIC
• Frequency-max: 500kHz
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

SG1842/SG1843 Series
12
Softstart and adjustable peak current can be done with the external
circuitry shown above.
The oscillator is programmed by the values selected for the timing
components R
calculation of the component values.
FIGURE 19. — ADJUSTABLE BUFFERED REDUCTION OF CLAMP LEVEL
I
t
where; V
SOFTSTART
C
PK
minimum line and maximum load conditions.
=
V
R
CS
S
R
R
= -ln 1 -
2
1
EAO
FIGURE 21. — OSCILLATOR CONNECTION
T
Where: V
SG1842/43
MPSA63
and C
Discharge
≡ voltage at the Error Amp Output under
8 (14)



Current
4 (7)
2 (3)
1 (1)
T
. Refer to application information for
V
5
2.8V
1.1V
CS
EAO



= 1.67
WITH SOFTSTART
R
- 1.3
1
R
SG1842/43
+R
1
2
I
d






= 8.2mA



R
P R O D U C T D A T A B O O K 1 9 9 6 / 1 9 9 7
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
1
5 (9)
R
+R



1
R
R
2
5V
1
1



+R
7 (12)
R
C
and V
2
2
8 (14)
4 (7)
U R R E N T
P



C
R O D U C T I O N
C.S.MAX
7 (11)
6 (10)
5 (8)
3 (5)
V
CC
R
C
T
= 1V (Typ.)
T
- M
V
IN
Q1
V
I
R
O D E
CS
S
P W M C
D
Precision duty cycle limiting as well as synchronizing several 1842/
1843's is possible with the above circuitry.
Error amplifier is capable of sourcing and sinking current up to 0.5mA.
A T A
O N T R O L L E R
FIGURE 20. — EXTERNAL DUTY CYCLE CLAMP AND
R
S
FIGURE 22. — ERROR AMPLIFIER CONNECTION
i
R
R
H E E T
A
B
R
f =
f =
F
6
2
³ 10K
R
MULTI-UNIT SYNCHRONIZATION
R
(R
F
A
A
(continued)
+ 2R
R
8
1.44
2 (3)
1 (1)
+ 2R
B
TIMER
B
555
B
)C
4
1
2.5V
SG1842/43
3
SGX842/43
To other
8 (14)
4 (7)
SG1842/43
0.5mA
Copyright © 2000
5 (9)
Rev. 1.6a 10/04