SG3844Y SEMICOA, SG3844Y Datasheet - Page 11
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SG3844Y
Manufacturer Part Number
SG3844Y
Description
Manufacturer
SEMICOA
Datasheet
1.SG3844Y.pdf
(12 pages)
Specifications of SG3844Y
Pwm Type
Current Mode PWM Controller
Number Of Pwm Outputs
1
On/off Pin
No
Adjustable Output
No
Switching Freq
500kHz
Duty Cycle
50%
Output Current
200mA
Synchronous Pin
No
Rise Time
50ns
Fall Time
50ns
Operating Temperature Classification
Commercial
Mounting
Through Hole
Pin Count
8
Package Type
CDIP
Lead Free Status / Rohs Status
Not Compliant
Available stocks
Company
Part Number
Manufacturer
Quantity
Price
Company:
Part Number:
SG3844Y
Manufacturer:
NEC
Quantity:
5 510
Copyright © 2000
Rev. 1.6c
The 1844/45 output stage can provide negative base current to
remove base charge of power transistor (Q
is accomplished by adding a capacitor (C
(R
The RC low-pass filter will eliminate the leading edge current spike
caused by parasitics of Power MOSFET.
1
). The resistor (R
»
FIGURE 14. — CURRENT SENSE SPIKE SUPPRESSION
R
SG1844/45
»
1
SG1844/45
V
| | R
FIGURE 16. — BIPOLAR TRANSISTOR DRIVE
C1
V
R
C
2
2
+
_
I
B
Pin numbers referenced are for 8-pin package and pin numbers in parenthesis are for 14-pin package.
7 (12)
1
) is to limit the base current during turn on.
V
C
7 (11)
6 (10)
5 (8)
3 (5)
7 (11)
6 (10)
5 (8)
3 (5)
V
CC
C
P R O D U C T D A T A B O O K 1 9 9 6 / 1 9 9 7
R
R
2
V
IN
1
C
Q1
R
) in parallel with a resistor
S
1
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
) for faster turn off. This
U R R E N T
P
V
C
R
C1
1
1
R O D U C T I O N
I
PK(MAX)
V
= 1.0V
IN
Q1
R
- M
S
R
I
PK
S
O D E
P W M C
D
A resistor (R
ringing caused by the MOSFET input capacitance and any inductance
in series with the gate drive. (Note: It is very important to have a
low inductance ground path to insure correct operation of the I.C.
This can be done by making the ground paths as short and as wide
as possible.)
Current transformers can be used where isolation is required
between PWM and Primary ground. A drive transformer is then
necessary to interface the PWM output with the MOSFET.
A T A
I
SG1844/45
PK
=
V (PIN 1) - 1.4
O N T R O L L E R
FIGURE 15. — MOSFET PARASITIC OSCILLATIONS
7 (12)
S
1
) in series with the MOSFET gate reduce overshoot and
3R
H E E T
FIGURE 17. — ISOLATED MOSFET DRIVE
SG1844/SG1845 Series
7 (11)
6 (10)
5 (8)
3 (5)
S
SG1844/45
V
CC
C
N
N
7 (12)
3 (5)
Boundary
Isolation
P
S
R
7 (11)
6 (10)
5 (8)
R
S
R
V
1
CC
N
V
S
IN
Q1
R
S
V
IN
Q1
N
P
+
0
+
_ 0
V
_
GS
50% DC
25% DC
Waveforms
11