参数资料
型号: SG3845DM
厂商: MICROSEMI CORP-ANALOG MIXED SIGNAL GROUP
元件分类: 稳压器
英文描述: CURRENT MODE PWM CONTROLLER
中文描述: 1 A SWITCHING CONTROLLER, 500 kHz SWITCHING FREQ-MAX, PDSO8
封装: ROHS COMPLIANT, PLASTIC, SOIC-8
文件页数: 12/12页
文件大小: 216K
代理商: SG3845DM
C
U R R E N T
-M
O D E
PWM C
O N T R O L L E R
SG1844/SG1845 Series
P R O D U C T D A T A B O O K 1 9 9 6 / 1 9 9 7
Copyright 2000
Rev. 1.4 4/00
12
P
R O D U C T I O N
D
A T A
S
H E E T
T Y P I C A L A P P L I C AT I O N C I R C U I T S
(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
PK
=
Where: 0
V
1
1.0V
t
SOFTSTART
= -ln1 -
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
1
C
2
6
R
B
R
A
1
8
4
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
d
= 8.2mA
R
T
1 (1)
R
F
R
i
2 (3)
R
F
10K
2.5V
SG1844/45
0.5mA
The oscillator is programmed by the values selected for the timing
components R
and C
. 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
A
+ 2R
B
)C
R
1.44
f =R
A
+ 2R
B
V
1
R
S
R
1
R
2
R
1
+R
2
1.43 - 0.23
1+
V
C
V
2
and V
1
=
where: V
2
=
R
1
R
2
R
1
R
2
0.5
1+
R
1
R
2
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