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參數(shù)資料
| 型號(hào)： | 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(guān)穩(wěn)壓器集成甲開關(guān) |
| 文件頁(yè)數(shù)： | 20/26頁(yè) |
| 文件大?。?/td> | 643K |
| 代理商： | SC2440TETRT |
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20
2005 Semtech Corp.
www.semtech.com
SC2440
POWER MANAGEMENT
Applications Information
In addition C
5
and R
5
form a zero with angular frequency:
KHz
22
Krads
140
pF
470
K
4
=
15
1
C
R
1
1
5
5
1
Z
=
=
=
ω
The
v
output-to-control
v
v
transfer
function
OUT
FB
FB
COMP
OUT
COMP
v
v
v
=
is also shown in Figure 13. Its mid-
band gain (between z
1
and p
3
) is
+
2
1
2
5
MA
R
R
R
R
G
. The
overall loop gain T(s) is the product of the control-to-
output and the output-to-control transfer functions. To
j
ω
Bode plot, the feedback network is
assumed to be resistive. If the overall loop gain is to
cross 0dB at one tenth of the switching frequency
f
10
(between z
1
and p
2
) will be
simplify
)
(
5
S
C
π
=
ω
=
ω
) at –20dB/decade, then its mid-band gain
n
10
R
C
R
C
n
10
OUT
1
S
OUT
1
S
2
p
c
ω
=
ω
=
ω
ω
.
This is also equal to
+
2
1
2
5
MA
OUT
MP
R
R
R
R
G
R
G
. Therefore
n
10
R
C
R
R
R
+
R
G
R
G
OUT
1
2
1
2
5
MA
OUT
MP
ω
=
.
Re-arranging,
MA
MP
1
S
2
1
5
G
nG
10
C
R
R
1
R
ω
+
=
(11)
ω
z1
is shown to be less than
ω
p2
in Figure 13. Making
ω
=
ω
gives a first-order estimate of C
5
:
R
C
C
=
(12)
2
p
1
z
5
)
MIN
(
OUT
nR
1
5
Notice that R
determines the mid-band loop gain of the
converter. Increasing R
5
increases the mid-band gain and
the crossover frequency. However it reduces the phase
margin. An estimate of R
and C
can be obtained from
(11) and (12) with n=1. The compensation is then checked
by measuring the loop gain and the phase or by observing
the inductor current and the output voltage during load
transient. Choose the largest R
and the smallest C
to
give at least 45
°
of phase margin. The corresponding
load transient should not show any ringing or excessive
overshoot (see Figures 14(c), 14(d), 17(b) and 17(c)). C
6
is a small ceramic capacitor (10-47pF) to roll off the loop
gain at high frequency. Feedforward capacitor C
boosts
phase margin over a limited frequency range and is
sometimes used to improve loop response. C
11
will be
more effective if
1
1
R
R
R
>>
2
.
Example: Determine the compensation components for
the 1.3MHz 12V to 5V and 3.3V converter in Figure 1.
For both channels,
S
2
=
ω
F
10
C
1
μ
=
. n is assumed to be 1 in (11) and (12).
1
Mrads
,
A
2
I
)
MAX
(
OUT
=
and
For the 3.3V output:
=
×
×
16
+
=
K
9
)
10
8
)
)
10
10
10
2
K
10
K
3
23
1
R
4
5
6
5
nF
1
)
2
K
9
16
)
V
3
10
C
5
5
=
=
For the 5V channel:
=
×
×
25
+
=
K
5
)
10
8
)
)
10
10
10
2
K
10
K
2
40
1
R
4
5
6
7
nF
1
)
2
K
5
25
)
V
5
10
C
5
8
=
=
C
and C
(both 10pF) are then added to increase gain
margin. Load transient responses of both channels are
observed using these values. There is very little inductor
current overshoot even with C
and C
reduced to 470pF
and 220pF respectively (Figure 14). The measured overall
loop gain and phase plots of the converter are also
shown.
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相關(guān)代理商/技術(shù)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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