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參數(shù)資料
| 型號： | SC4806MLTRT |
| 廠商： | Semtech Corporation |
| 英文描述： | Multiple Function Double Ended PWM Controller |
| 中文描述： | 多功能雙端PWM控制器 |
| 文件頁數(shù)： | 10/22頁 |
| 文件大?。?/td> | 485K |
| 代理商： | SC4806MLTRT |
10
2006 Semtech Corp.
www.semtech.com
SC4806
POWER MANAGEMENT
Application Information (Cont.)
OUTA (PWM1)
OUTB (PWM1)
OUTA (PWM2)
OUTB (PWM2)
FEED BACK
The error signal from output of an external error ampli-
fier such as SC431 or SC4431 is applied to the inverting
input of the PWM comparator at the FB pin either di-
rectly or via an opto-coupler for the isolated applications.
For best stability, keep the FB trace length as short as
possible.
FB
SC431
-Vo
+Vo
+
Co1
Lo1
REF
The signal at the FB pin is then compared to the 3X sig-
nal from the current sense/ slope compensation RAMP
pin. Matched out of phase signals are generated to con-
trol the OUTA and OUTB gate drives of the two phases. A
single ramp signal is used to generate the control signals
for both phases, hence achieving a tightly matched per
phase operation.
Voltages below 1.5V at the FB pin, will produce a 0%
duty cycle at the OUTA/OUTB gate drives. This offset is to
provide enough head room for the opto coupler used in
isolated applications.
GATE DRIVERS
OUTA and OUTB are out of phase bipolar gate drive out-
put stages, that are supplied from VCC and provide a
peak source/sink current of about 100mA. Both stages
are capable of driving the logic input of external MOSFET
drivers or a NPN/PNP transistor buffer. The output stages
switch at half the oscillator frequency. When the voltage
on the RC pin is rising, one of the two outputs is high, but
during fall time, both outputs are off. This “dead time”
between the two outputs, along with a slower output rise
and fall time, insures that the two outputs can not be on
at the same time. The dead time is programmable and
depends upon the timing capacitor.
It should be noted that if high speed/high current drivers
such as the SC1301 are used, careful layout guide lines
must be followed in order to minimize stray inductance,
which might cause negative voltages at the output of
the drivers. This negative voltage can be clamped to a
reasonable level by placing a small Schottky diode di-
rectly at the output of the driver as shown below:
Vcc
G
9
ILIM
5
OUTB
10
F
7
L
1
VCC
12
S
2
S
3
RC
4
R
8
RAMP
6
OUTA
11
G
0
M aster
S C 4806
Cosc2
Rosc2
REF
Vcc
G
9
ILIM
5
OUTB
10
F
7
L
1
VCC
12
S
2
S
3
RC
4
R
8
RAMP
6
OUTA
11
G
0
S lave
S C 4806
Cosc1
Rosc1
REF
D_B1
Gate_A
G
9
ILIM
5
OUTB
10
F
7
L
1
VCC
12
S
2
S
3
RC
4
R
8
RAMP
6
OUTA
11
G
0
S C 4806
VCC
1
4
3
2
5
SC1301A
VCC
1
4
3
2
5
SC1301A
D_B2
Gate_B
D_A1
D_A2
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PDF描述 |
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| SC4808A | High Performance Dual Ended PWM Controller |
| SC4808AIMSTR | High Performance Dual Ended PWM Controller |
| SC4808AIMSTRT | High Performance Dual Ended PWM Controller |
| SC4808B | High Performance Dual Ended PWM Controller |
| SC4808BIMSTR | High Performance Dual Ended PWM Controller |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| SC4808A | 制造商:SEMTECH 制造商全稱:Semtech Corporation 功能描述:High Performance Dual Ended PWM Controller |
| SC4808AIMSTR | 制造商:SEMTECH 制造商全稱:Semtech Corporation 功能描述:High Performance Dual Ended PWM Controller |
| SC4808AIMSTRT | 制造商:Semtech Corporation 功能描述: |
| SC4808B | 制造商:SEMTECH 制造商全稱:Semtech Corporation 功能描述:High Performance Dual Ended PWM Controller |
| SC4808B-1 | 制造商:SEMTECH 制造商全稱:Semtech Corporation 功能描述:High Performance Dual Ended PWM Controller |
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