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參數(shù)資料
| 型號： | SC2441ATETRT |
| 廠商： | Semtech Corporation |
| 英文描述： | 1.8V to 20V Input 2-Phase Synchronous Step-down Controllers with Step-up Converter |
| 中文描述： | 1.8V至20V的輸入2相同步降壓與升壓轉(zhuǎn)換器控制器 |
| 文件頁數(shù)： | 29/37頁 |
| 文件大小： | 1024K |
| 代理商： | SC2441ATETRT |
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29
2006 Semtech Corp.
www.semtech.com
POWER MANAGEMENT
Applications Information
impedance is R
in
and the input capacitor C
has an ESR
denoted as R
. MOSFET and input capacitor current
waveforms, ESR voltage ripple and input voltage ripple
are shown in Figure 19.
SC2441A
Figure 19. Typical waveforms at the input of a
buck converter.
It can be seen that the current in the input capacitor
pulses with high di/dt. Capacitors with low ESL should be
used. It is also important to place the input capacitor
close to the MOSFET’s on the PC board to reduce trace
inductances around the pulse current loop.
The RMS value of the capacitor current is approximately
].
)
D
1
D
)
D
1
)(
12
1
[(
D
I
I
2
2
2
o
Cin
The power losses at the input capacitors is then
P
Cin
= I
Cin
2
R
esr
.
For reliable operation
,
the maximum power dissipation
in the capacitors should not result in more than 10
o
C of
temperature rise. Many manufacturers specify the
maximum allowable ripple current (ARMS) rating of the
capacitor at a given ripple frequency and ambient
temperature. The input capacitance should be high
enough to handle the ripple current. For higher power
applications, multiple capacitors are placed in parallel to
increase the ripple current handling capability.
Sometimes meeting tight input voltage ripple
specifications may require the use of larger input
capacitance. At full load, the peak-to-peak input voltage
ripple due to the ESR is
.
I
2
1
R
v
o
esr
ESR
The peak-to-peak input voltage ripple due to the capacitor
is
.
f
C
DI
v
s
in
o
C
From these two expressions, C
can be found to meet
the input voltage ripple specification. In a multi-phase
converter, channel interleaving can be used to reduce
ripple. The two step-down channels of the SC2441A
operate at 180 degrees from each other. If both step-
down channels in the SC2441A are connected in parallel,
both the input and the output RMS currents will be
reduced.
Ripple cancellation effect of interleaving allows the use
of smaller input capacitors. When converter outputs are
connected in parallel and interleaved, smaller inductors
and capacitors can be used for each channel. The total
output ripple-voltage remains unchanged. Smaller
inductors speeds up output load transient.
When two channels with a common input are interleaved,
the total DC input current is simply the sum of the
individual DC input currents. The combined input current
waveform depends on duty ratio and the output current
waveform. Assuming that the output current ripple is
small, the following formula can be used to estimate the
RMS
value of the ripple current in the input capacitor.
Let the duty ratios and output currents of Channel 1 and
Channel 2 be D
1
, D
2
and I
o1
, I
o2
respectively.
If D
1
<0.5 and D
2
<0.5, then
.
I
D
I
D
I
2
2
o
2
2
1
o
1
Cin
If D
1
>0.5 and (D
1
-0.5) < D
2
<0.5, then
.
I
5
D
D
(
)
I
I
)(
5
D
(
I
I
2
2
o
1
2
2
2
o
1
o
1
2
1
o
Cin
If D
1
>0.5 and D
2
< (D
1
-0.5) < 0.5, then
.
I
5
D
D
(
)
I
I
2
D
I
I
2
2
o
2
1
2
2
o
1
o
2
1
o
Cin
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| SC2441 | Very Low Input Voltage 2-Phase Synchronous Step-down Controllers with Step-up Converter |
| SC2441EVB | Very Low Input Voltage 2-Phase Synchronous Step-down Controllers with Step-up Converter |
| SC2441ITSTRT | Very Low Input Voltage 2-Phase Synchronous Step-down Controllers with Step-up Converter |
| SC2442 | High Performance Wide Input Range Dual Synchronous Buck Controller |
| SC2442H | High Performance Wide Input Range Dual Synchronous Buck Controller |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| SC2441EVB | 制造商:SEMTECH 制造商全稱:Semtech Corporation 功能描述:Very Low Input Voltage 2-Phase Synchronous Step-down Controllers with Step-up Converter |
| SC2441ITSTRT | 制造商:Semtech Corporation 功能描述:Controller IC |
| SC2442 | 制造商:SEMTECH 制造商全稱:Semtech Corporation 功能描述:High Performance Wide Input Range Dual Synchronous Buck Controller |
| SC2442H | 制造商:SEMTECH 制造商全稱:Semtech Corporation 功能描述:High Performance Wide Input Range Dual Synchronous Buck Controller |
| SC2442HITSTR | 制造商:Semtech Corporation 功能描述: |
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