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參數(shù)資料
| 型號： | SC2441A |
| 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)： | 27/37頁 |
| 文件大?。?/td> | 1024K |
| 代理商： | SC2441A |
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27
2006 Semtech Corp.
www.semtech.com
POWER MANAGEMENT
Applications Information
SC2441A
b) Select inductance value: Sometimes the calculated
inductance value is not available off-the-shelf. The
designer can choose the adjacent (larger) standard
inductance value. The inductance varies with
temperature and DC current. It is a good engineering
practice to re-evaluate the resultant current ripple at
the rated DC output current.
c) Current rating: The saturation current of the inductor
should be at least 1.5 times of the peak inductor current
under all conditions.
Output Capacitor (C
o
) and V
out
Ripple in Step-down
Sections
The output capacitor provides output current filtering in
steady state and serves as a reservoir during load
transient.
The output capacitor can be modeled as an
ideal capacitor in series with its parasitic ESR (R
esr
) and
ESL (L
esl
) (Figure 16).
Figure 16. C
o
equivalent circuit
If the current through the branch is i
b
(t), the voltage
across the terminals will then be
).
t
b
i
R
dt
)
b
di
L
dt
)
b
i
C
1
V
)
o
v
esr
t
0
esl
o
o
This basic equation illustrates the effects of ESR, ESL
and C
o
on the output voltage.
The first term is the DC voltage across C
at time t=0.
The second term is the ripple-voltage caused by the
inductor ripple-current. The third term is the voltage ripple
due to ESL and the fourth term is the voltage ripple due
to ESR. The total output voltage ripple is then a
vector
sum of the last three terms.
Since the inductor current is a triangular waveform with
peak-to-peak value
δ
*
I
o
, the ripple-voltage caused by
inductor current ripples is
.
f
C
8
I
v
s
o
o
C
The ripple-voltage due to ESL is
D
I
f
L
v
o
s
esl
ESL
and the ESR ripple-voltage is
.
I
R
v
o
esr
ESR
Aluminum capacitors (e.g. electrolytic, solid OS-CON,
POSCAP, tantalum) have high capacitances and low
ESL’s. The ESR has the dominant effect on the output
ripple voltage. It is therefore very important to minimize
the ESR.
When determining the ESR value, both the steady state
ripple-voltage and the dynamic load transient need to be
considered. To keep the steady state output ripple-voltage
<
V
o
, the ESR should satisfy
.
I
V
R
o
o
1
esr
To limit the dynamic output voltage overshoot/
undershoot within
α
(say 3%) of the steady state output
voltage) under 0 to full load current swing, the ESR value
should be
.
I
V
R
o
o
2
esr
The required ESR value of the output capacitors should
be
R
esr
= min{R
esr1
,R
esr2
}.
In the aluminum capacitor selection, the working voltage
rating is normally suggested to be greater than 1.5
V
o
.
The allowable current ripple (RMS) should be greater than
Co
Lesl
Resr
i
b
(t)
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| SC2441AEVB | 1.8V to 20V Input 2-Phase Synchronous Step-down Controllers with Step-up Converter |
| SC2441ATETRT | 1.8V to 20V Input 2-Phase Synchronous Step-down Controllers with Step-up Converter |
| 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 |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| SC2441A_09 | 制造商:SEMTECH 制造商全稱:Semtech Corporation 功能描述:1.8V to 20V Input 2-Phase Synchronous Step-down Controllers with Step-up Converter |
| SC2441AEVB | 制造商:SEMTECH 制造商全稱:Semtech Corporation 功能描述:1.8V to 20V Input 2-Phase Synchronous Step-down Controllers with Step-up Converter |
| SC2441ATETRT | 制造商:Semtech Corporation 功能描述: |
| 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 |
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