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參數(shù)資料
| 型號： | SC2440TETRT |
| 廠商： | Semtech Corporation |
| 英文描述： | 2.5 MHz Dual Switching Regulator with Integrated 2A Switches |
| 中文描述： | 2.5 MHz雙開關穩(wěn)壓器集成甲開關 |
| 文件頁數(shù)： | 9/26頁 |
| 文件大?。?/td> | 643K |
| 代理商： | SC2440TETRT |
9
2005 Semtech Corp.
www.semtech.com
SC2440
POWER MANAGEMENT
Applications Information
Setting the Output Voltage
The regulator output voltage is set with an external
resistive divider (Figure 4) with its center tap tied to the
FB pin.
VOUT
R1
15nA
)
V
2
R
R
OUT
1
=
(1)
The percentage error due the input bias current of the
error amplifier is
V
1
)
R
R
100
nA
15
V
V
2
1
OUT
OUT
=
.
Example: Determine the output voltage error of a
V
5
V
OUT
=
converter with
R
2
=
K
1
51
.
From (1),
=
=
K
205
)
5
K
1
51
R
1
%
061
.
V
1
)
K
205
K
1
51
(
100
nA
15
V
V
OUT
OUT
=
=
.
This error is at least an order of magnitude lower than
the ratio tolerance resulting from the use of 1% resistors
in the divider string.
Choosing the Operating Frequency
The free-running frequency of the master oscillator is
set with an external resistor from the ROSC pin to ground.
Channel frequency is one-half of that of the master
oscillator. A graph of channel frequency against R
is
shown in the “Typical Performance Characteristics”.
Before choosing the operating frequency, tradeoffs
among efficiency, operating duty cycle, component size
and EMI interferences must be considered. High
frequency operation reduces the size of passive
components but switching losses are higher. Lowering
the switching frequency improves efficiency. However the
required inductor and capacitor are larger. Channel
frequencies between 1 and 2MHz are good compromises.
In order to quantify the tradeoff between switching
frequency and efficiency, the 12V to 5V DC-DC converter
in Figure 1 is modified to run at 500KHz and 2.5MHz
while keeping the inductor ripple current constant. The
modified component values are tabulated in Table 1 and
efficiencies at these frequencies are shown in Figure 5.
The efficiency of the 1.3MHz 5V regulator in Figure 1 is
also plotted for the ease of comparison. The efficiency
at 500KHz is only marginally higher than that at 1.3MHz.
The peak efficiency at 2.5MHz is only 2% lower compared
to those at lower frequencies.
R2
FB
SC2440
Figure 4. V
OUT
is set with a Resistive Divider
f
)
H
M
(
R
9
K
(
)
L
2
(
μ
)
H
R
7
K
(
)
C
8
)
p
C
9
)
p
5
6
5
)
0
1
7
R
D
s
c
o
C
0
1
4
1
0
7
4
2
2
3
0
1
)
1
0
4
0
D
o
c
F
4
4
3
2
0
2
2
0
1
5
2
0
)
R
2
4
R
C
a
d
m
u
S
7
4
3
0
2
2
0
1
Table 1. The 12V to 5V Converter in Figure 1 is modified
to run at Different Frequencies.
Efficiency vs Load Current
75
80
85
90
0.0
0.5
1.0
1.5
2.0
Load Current (A)
E
V
IN
=12V
V
OUT
=5V
2.5MHz
1.3MHz
500KHz
Figure 5. Efficiencies of 500KHz, 1.3MHz and 2.5MHz
12V to 5V Step-down Converters.
相關PDF資料 |
PDF描述 |
|---|---|
| SC2441A | 1.8V to 20V Input 2-Phase Synchronous Step-down Controllers with Step-up Converter |
| 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 |
相關代理商/技術參數(shù) |
參數(shù)描述 |
|---|---|
| SC2441 | 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 |
| SC2441A | 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 |
| 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: |
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