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參數(shù)資料
| 型號： | SC480EVB |
| 廠商： | Semtech Corporation |
| 英文描述： | Complete DDR1/2/3 Memory Power Supply |
| 中文描述： | 完全DDR1/2/3內(nèi)存供電 |
| 文件頁數(shù)： | 11/25頁 |
| 文件大?。?/td> | 858K |
| 代理商： | SC480EVB |
11
2006 Semtech Corp.
www.semtech.com
POWER MANAGEMENT
SC480
Referencing Figure 2, the equation for setting the output
voltage is:
5
R3
2
R
1
V
)
(
UT
O
x
Current Limit Circuit
Current limiting of the SC480 can be accomplished in two
ways. The on-state resistance of the low-side MOSFETs
can be used as the current sensing element, or a sense
resistor in the low-side source can be used if greater ac-
curacy is desired. RDSON sensing is more ef
fi
cient and
less expensive. In both cases, the R
resistor between
the ILIM pin and LX sets the over-current threshold. This
resistor R
is connected to a 10
μ
A current source within
the SC480 which is turned on when the low-side MOSFET
turns on. When the voltage drop across the sense resistor
or low-side MOSFET equals the voltage across the R
resis-
tor, current limit will activate. The high-side MOSFET will
not be allowed to turn on until the voltage drop across the
sense element (resistor or MOSFET) falls below the voltage
across the R
ILIM
resistor.
The current sensing circuit actually regulates the inductor
valley current, see Figure 3. This means that if the current
limit is set to 10A, the peak current through the inductor
would be 10A plus the peak ripple current, and the average
current through the inductor would be 10A plus 1/2 the
peak-to-peak ripple current.
I
LIMIT
I
LOAD
I
PEAK
I
TIME
Valley Current
-
Limit Threshold Point
Figure 3
Application Information
D1
Vout
+5V
+VIN
L1
+
C1
Q2
+
C3
D2
R1
PGND
DL
VDDP
ILIM
LX
DH
BST
C2
Q1
SC480
Figure 4
The schematic of RDS
sensing circuit is shown in Figure
4 with R
ILIM
= R1 and RDS
ON
of Q2.
Similarly, for resistor sensing, the current through the lower
MOSFET and the source sense resistor develops a voltage
that opposes the voltage developed across R
. When the
voltage developed across the R
resistor reaches voltage
drop across R
an over-current exists and the high-side
MOSFET will not be allowed to turn on. The over-current
equation when using an external sense resistor is:
SENSE
R
ILIM
R
A
10
Valley
OC
IL
x
Schematic of resistor sensing circuit is shown in Figure 5
with R
ILIM
= R1 and R
SENSE
= R4.
Figure 5
Q1
Q2
+
C1
Vout
D1
R1
+5V
L1
+
C3
R4
D2
PGND
DL
VDDP
ILIM
LX
DH
BST
+VIN
C2
SC480
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| SC480IMLTRT | Complete DDR1/2/3 Memory Power Supply |
| SC4810B | High Performance Current Mode PWM Controller with Complementary Output, Programmable Delay |
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| SC480IMLTRT | 制造商:SEMTECH 制造商全稱:Semtech Corporation 功能描述:Complete DDR1/2/3 Memory Power Supply |
| SC4810B | 制造商:SEMTECH 制造商全稱:Semtech Corporation 功能描述:High Performance Current Mode PWM Controller with Complementary Output, Programmable Delay |
| SC4810BIMLTRT | 制造商:Semtech Corporation 功能描述:Controller IC Leaded Process Compatible: |
| SC4810BITSTRT | 制造商:Semtech Corporation 功能描述:Controller IC |
| SC4810E | 制造商:SEMTECH 制造商全稱:Semtech Corporation 功能描述:High Performance Current Mode PWM Controller with Complementary Output, Programmable Delay |
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