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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)： | 24/37頁 |
| 文件大?。?/td> | 1024K |
| 代理商： | SC2441A |
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24
2006 Semtech Corp.
www.semtech.com
POWER MANAGEMENT
Applications Information
SC2441A
DCR Current Sensing
Either precision sense resistor or inductor DCR can be
used as the inductor current sensing element.
Figure 12. Current Sensing Circuit.
In Figure 12 SW1 and SW2 represent the MOSFET
switches. CS is the current sense amplifier. I
and I
are the input bias currents of the CS. L
is the output
inductor. R
is the DC resistance of L
. R
, R
3
and C
1
constitute the DCR current sensing network.
Assuming that CS input bias currents are zero and that
R
is not used, if the time constant L
/R
is made equal
to the time constant R
C
, then the voltage across the
inductor DCR, R
, will be replicated across C
in the steady
state (see Figure 13). The following equations apply:
/2
I
I
I
1
L
O
PEAK
L1
.
/2
I
I
I
1
L
O
VALLEY
L1
.
1
L1
I
C1
R
(t)
(t)
V
where, I
O
is the output current and
peak L
current ripple. The inductor current can therefore
be sensed by monitoring C
1
voltage. L should be selected
so that the
is between 25% to 33% of the I
O
.
1
L
I
is the peak-to-
However CS input bias currents are not zero. I
and I
are typically 0.4
μ
A and 40
μ
A respectively (see electrical
characteristics) and can not be ignored.
Figure 13. Voltage Waveform C
1
and R
1
In Figure 12, R
2
and R
3
resistive divider attenuates the
sensed signals when I
constant resulting from L
1
and its DCR R
1
is:
Define R
EQU
:
. The time
The time constant of the DCR sensing network is:
If
τ
C1
=
τ
L1
,
then the peak and valley voltages across
C
1
will be:
2
I
R
R
(
R
R
R
I
V
O
3
2
1
3
EQU
CS
VALLEY
C1
L1
I
)
I
therefore introduces an offset error to the sensed
voltage. To reduce this error, R
EQU
must be minimized.
Suppose V
=5V; V
=2.5V; D=50%; I
=20A;
F
=500KHz; L
=0.5
μ
H; R
=2m
;
I
=1
μ
A. The output
current limit is set at 28A. The time constant formed by
L
1
and R
1
is
1
1
1
L1
C
3
R
2
R
3
R
2
R
0.25ms
R
L
5A
I
1
L
25mV
I
2
28A
L1
R
R
(
R
R
R
I
V
3
2
1
3
EQU
CS
PEAK
C1
)
0
t
Voltage Drop on R
1
--- I
L1
(t)R
1
Voltage on C
1
--- V
C1
(t)
V
V
C1.PEAK
V
C1.VALLEY
R
1
I
L1.PEAK
R
1
I
L1.VALLEY
R
1
I
O
SC2441A
SW1
SW2
L
1
R
1
R
2
C
1
R
3
+
-
CS
+
V
C1
-
C
OUT
R
LOAD
V
IN
I
CS+
I
CS-
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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