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參數(shù)資料
| 型號： | SC2441ATETRT |
| 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)： | 25/37頁 |
| 文件大?。?/td> | 1024K |
| 代理商： | SC2441ATETRT |
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25
2006 Semtech Corp.
www.semtech.com
POWER MANAGEMENT
Applications Information
SC2441A
Pre-biased Start Up
Sometimes the step-down converter is to start into a
pre-biased output load. The pre-biased voltage is normally
lower than the output setpoint of the step-down
converter.
As described earlier, pre-bias startup process with the
SC2441A is seamless. The testing setup of the pre-biased
start-up is shown as in Figure 14.
D1
V
s
Blocking Diode
External
Voltage
Source
Module
under
Test
+
-
R
LOAD
V
O
Figure 14. Test Setup for Pre-biased Start Up
In Figure 14, V
is the external power supply pre-biasing
V
. D
blocks the output of the power module under test
from V
during soft-start. R
is the resistive load of the
module under test. Before power-up the module, monitor
V
to ensure that it is the desired pre-biased output
voltage. Then power-up the module. V
O
should rise
smoothly.
Free-running Operation
The internal oscillator of the SC2441A can either free-
run or it can be phase-locked to an external clock.
In free-running mode, the internal phase-locked loop is
disabled by tying an external resistor from the PLLF pin
to V
. The external resistor ROSC (see figure 5(a))
programs the channel frequency. The PLLF pull-up resistor
should be carefully selected so that the voltage at the
PLLF pin is above 1V. A value between 20K
to 50K
is
recommended.
Pull-up resistor can also be tied to V
if V
is present
before the SC2441A starts to switch. The advantage tying
the pull-up resistor to V
is because that the V
is a
regulated output from either a boost converter or a sepic
converter. The resistor from the PLLF pin can be tied to
V
if V
is from a boost converter output. The reason is
that the V
will be powered up from the input V
before
output of the boost converter reaches the setpoint.
However, in some applications, a SEPIC converter is
employed to get stable V
due to the wide input voltage
range. In this case, the resistor from the PLLF pin should
not be connected to the V
due to the presence of a DC
blocking capacitor in the converter. The SC2441A will not
switch if the PLLF pin is at zero volt.
Applying more than 2.1V at the PLLF pin activates the
diode clamp circuit (see Figure 5(a)). The filtering
components (R
,R
, C
and C
in Figure 5(a)) are not
needed while free-running. The clamp activation will have
no effect on the PLL if V
PLLF
>1V.
The internal clock is brought out to the CKOUT pin. The
signal at CKOUT pin can be used as the synchronizing
clock for other SC2441As in a master-slave configuration.
0.25ms
C
3
R
2
R
3
R
2
R
1
25mV
5A
2
28A
μ
R
R
R
R
R
R
R
R
A
1
3
2
1
3
3
2
2
3
)
(
)
(
With an arbitrary selection of
3.01K
3
R
2
R
3
R
2
R
, we can
get C
=83nF. Since 83nF is not a standard capacitance
value, we use 100nF capacitor for C
1
. Consequently,
R
2
2.5
. And we can also derive:
K
3
R
2
R
3
R
25mV
5A
2
28A
μ
2.5K
R
R
2.5K
A
1
2
1
6.80K
2
R
3.92K
3
R
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| 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 |
| SC2442 | High Performance Wide Input Range Dual Synchronous Buck Controller |
| SC2442H | High Performance Wide Input Range Dual Synchronous Buck Controller |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)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 |
| SC2442 | 制造商:SEMTECH 制造商全稱:Semtech Corporation 功能描述:High Performance Wide Input Range Dual Synchronous Buck Controller |
| SC2442H | 制造商:SEMTECH 制造商全稱:Semtech Corporation 功能描述:High Performance Wide Input Range Dual Synchronous Buck Controller |
| SC2442HITSTR | 制造商:Semtech Corporation 功能描述: |
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