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參數(shù)資料
| 型號： | SC2441EVB |
| 廠商： | Semtech Corporation |
| 英文描述： | Very Low Input Voltage 2-Phase Synchronous Step-down Controllers with Step-up Converter |
| 中文描述： | 非常低的輸入電壓2相同步降壓與升壓轉(zhuǎn)換器控制器 |
| 文件頁數(shù)： | 25/35頁 |
| 文件大?。?/td> | 733K |
| 代理商： | SC2441EVB |
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25
2005 Semtech Corp.
www.semtech.com
POWER MANAGEMENT
Applications Information (Cont.)
SC2441
Given the input voltage V
, the output voltage V
and
the load current I
o3
, the following circuit parameters are
to be determined.
Inductor Selection
For a specified inductor current ripple (peak-to-peak)
δ
3
,
the inductor value is
.
V
V
)
V
V
1
I
f
V
δ
L
3
o
in
3
o
in
3
o
3
3
s
in
3
=
If V
= 3.3V, V
o3
= 5V and I
o3
= 1A with
δ
3
= 0.3 and f
s3
=
1MHz, then, L
= 2.5
μ
H.
For operation above 1MHz, Ferrite core material should
be used for lower core losses and better circuit efficiency.
The peak inductor current is
(1+0.5*
δ
3
)I
o3
.
The saturation current rating of the selected inductor
should be at least 1.2~1.5 times of the calculated peak
current value. In the example above, the peak inductor
current is 1.74A.
Capacitor Selection
Input capacitor
: The input capacitance should be large
such that the input transients due to both the step-up
and the step-down converters do not trip the UVLO
threshold 1.59V. Since the SC2441 controls a 2-phase
low input voltage step-down converter, the input
capacitance is sized to handle the input ripple current of
the buck converter. This is usually sufficient for the auxiliary
boost converter because the input current in a boost
converter is continuous. A small (< 1uF) ceramic bypass
capacitor can be soldered close to the PVIN pin for high
frequency filtering.
Output capacitor:
Unlike buck converter, pulse current is
delivered to the output of a boost converter. To reduce the
output ripple voltage, low ESR capacitors should be used.
The output capacitor should also be able handle the output
ripple current. The SC2441 is designed to use multi-layer
ceramic capacitor as the sole output capacitor.
Maximum Output Current
Figure 4 shows that the boost switch current is sensed
with an internal sense resistor Rs. With a current limit
threshold voltage of 14mV, the maximum output current
is
.
)
2
1
s
R
mV
14
)
δ
+
D
1
I
3
3
max
,
o
=
The boost switch current limit is internally set at 1.7A.
Voltage Feedback
With the internal reference voltage V
ref3
=1.25V, the voltage
feedback gain is
.
25
.
5
25
.
V
V
h
3
o
3
ref
3
=
=
=
The values of the feedback resistors can be determined
from the equation in “Setting the Output Voltage” section.
Loop Compensation
A simple small signal model for current-mode boost
converter in continuous-conduction mode is shown in
Figure 17.
Figure 17. Small signal model of Boost converter.
3
O
2
3
3
3
R
)
D
I
SL
I
)
D
I
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| 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 |
| SC2442HITSTR | High Performance Wide Input Range Dual Synchronous Buck Controller |
| SC2442HITSTRT | 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 |
|---|---|
| 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: |
| SC2442HITSTRT | 制造商:Semtech Corporation 功能描述:Controller IC |
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