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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) |
| 文件頁數(shù)： | 18/26頁 |
| 文件大小： | 643K |
| 代理商： | SC2440TETRT |
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18
2005 Semtech Corp.
www.semtech.com
SC2440
POWER MANAGEMENT
Applications Information
is no voltage at the switching regulator output or current
in the PGOOD pull-up resistor. If the PGOOD output high
level (= V
) is unacceptably low, then power good pull-
up from the input or a separate power supply will be the
only choice.
Sequencing the Outputs
As mentioned above, pulling either soft-start pin low with
an external transistor shuts off the corresponding
regulator (Figure 11). Releasing the soft-start pin enables
that channel and allows it to start. Delaying the release
of the soft-start pin of one channel with respect to the
other is a straightforward way of sequencing the outputs.
Figure 11(a) shows this method using two external
transistors M
and M
. M
is turned off first, allowing
channel 1 to start. Channel 2 is then enabled after time
T
D
.
The PGOOD output of one channel can also be used in
conjunction with the soft-start pin of the other channel
to delay start of that regulator. This method is depicted
in Figure 11(b). SS2 is pulled low and channel 2 is kept
off until channel 1 output rises to 90% of its set voltage.
A drawback of this approach is that only PGOOD2 is
available as a logic output.
Loop Compensation
Figure 12 shows a simplified equivalent circuit of a step-
down converter. The power stage, which consists of the
current-mode PWM comparator, the power switch, the
freewheeling diode and the inductor, feeds the output
network. The power stage can be modeled as a voltage-
controlled current source, producing an output current
proportional to its controlling input V
. Its
transconductance G
MP
is 5.7
-1
. With the current loop
closed, the control-to-output transfer function
COMP
OUT
v
v
has
a dominant-pole p
located at a frequency slightly higher
than that of the output filter pole.
1
OUT
1
OUT
V
OUT
C
2
p
C
R
n
nI
=
≈
ω
(8)
where C
1
is the output capacitor, R
OUT
is the equivalent
load resistance and n (depending on duty ratio, slope
compensation, frequency and passive components) is
usually between 1 and 2.
If C
is ceramic, then its ESR zero can be neglected as it
situates well beyond half the switching frequency. The
low frequency gain of the control-to-output transfer
function is simply the product of power stage
transconductance and the equivalent load resistance
(Figure 13).
The transfer functions of the feedback network and the
error amplifier are:
POWER
STAGE
GMP = 5.7
REFERENCE
VOLTAGE
1V
+
-
R5
C5
C6
RO
R2
COMP
R1
FB
C11
ESR
C1
R
OUT
V
OUT
V
IN
I
OUT
-1
GMA =
280
μ
-1
V
Figure 12. Simplified Control Loop Equivalent Circuit
相關(guān)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(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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