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參數(shù)資料
| 型號： | SC1401 |
| 廠商： | Semtech Corporation |
| 英文描述： | High Performance Synchronous Buck Controller with LDO for Portable Power(用于便攜式電源帶低壓差輸出的高性能同步步降控制器（1.25-5.5V可調(diào)輸出）) |
| 中文描述： | 高性能同步降壓控制器用于便攜式電源穩(wěn)壓器（用于便攜式電源帶低壓差輸出的高性能同步步降控制器（1.25 - 5.5V的可調(diào)輸出）） |
| 文件頁數(shù)： | 15/17頁 |
| 文件大?。?/td> | 268K |
| 代理商： | SC1401 |
15
2001 Semtech Corp.
www.semtech.com
POWER MANAGEMENT
Application Information (Cont.)
SC1401
The inductance and duty cycle equation excludes any
resistive drops due to winding resistance and MOSFET
on resistance.
Where:
L1 = 4μH
From this calulation we choose L1 to be 3.9μH.
For a lower operating frequency, f = 200kHz, L1 calulates
to be 6μH.
Choosing Inductor & FET Current Rating
The current carring capability of the inductor and MOSFETs
should be sized to handle the maximum current of the
supply set by the current sense resistor. For the SC1401
EVAL board RSENSE equals the paralled combination of
R7A & R7B. Here we use the minimum current threshold
value:
mV
100
R
=
Where I
PEAK
equals:
I
PEAK
= 7 + 0.75
I
PEAK
= 7.75 Amps
Here we choose a sense resistor of 13.5 milliohms. Now
we can determine FET and inductor current carrying
capability by using the maximum current limit threshold:
From this value choose an inductor with Isat > 10.4 Amps,
and for the FET choose a continuous conduction current
rating > 10.4 Amps.
Input Capacitor Selection
Input capacitor is selected based upon the input ripple
current demands of the converter. First determine the
input ripple current expected and then choose a capacitor
to meet that demand.
The input RMS ripple current can be calculated as follows:
I
RMS
= 3.3 Amps
The worse case input RMS ripple current occurs at 50%
duty cycle (D = 0.5 or V
= 2 V
) and therefore under
this condition the IRMS ripple current can be
approximated by:
However, this condition will not occur because the duty
cycle is set by V
/V
, 2/6 = 0.33. If the output voltage is
changed where D approached 50% the input capacitor
ripple current may need to be recalculated and capacitors
added.
Therefore, for a maximum load current of 7 amps, the
input capacitors should be able to safely handle 3.3 amps
of ripple current.
For the EVAL board, we choose four 22μF, 35V Tantalum
capacitors. Each capacitor has a ripple current capability
of 0.908 amps at 100kHz, 25°C. Four of these
capacitors in parallel will meet the requirements.
MOSFET Switches
After selecting the voltage and current requirements of
each MOSFET device for the upper and lower switches,
the next step is to determine their power handling
capability. For the EVAL board the IRF7805 meets the
voltage and current requirements. However, the lower
FET is a combination of two IRF7805 devices in parallel
for improved efficiency and to handle any possible short
kHz
300
f
and
,
f
1
t
V
D
IN
O
=
=
=
V
1.5
10
3.33
28
2.0
)
(28
L1
6
=
2
I
I
I
O
O
PEAK
+
=
PEAK
I
SENSE
A
4
10
0135
.
14
.
I
PEAK
=
=
)
V
(V
V
V
I
I
O
IN
O
IN
O
RMS
=
2)
-
(6
2
6
7
I
RMS
=
2
I
I
O
RMS
=
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| SC1402 | Multi-Output, Low-Noise Power Supply Controller for Notebook Computers |
| SC1402ISS | Multi-Output, Low-Noise Power Supply Controller for Notebook Computers |
| SC1403ITSTRT | Mobile Multi-Output PWM Controller with Lossless Current Sense |
| SC1403 | Mobile Multi-Output PWM Controller with Virtual Current SenseTM |
| SC1403ITSTR | Mobile Multi-Output PWM Controller with Virtual Current SenseTM |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| SC1401ISS | 制造商:SEMTECH 制造商全稱:Semtech Corporation 功能描述:HIGH PERFORMANCE SYNCHRONOUS BUCK CONTROLLER WITH LDO FOR PORTABLE POWER |
| SC1402 | 制造商:SEMTECH 制造商全稱:Semtech Corporation 功能描述:Multi-Output, Low-Noise Power Supply Controller for Notebook Computers |
| SC1402ISS | 制造商:SEMTECH 制造商全稱:Semtech Corporation 功能描述:Multi-Output, Low-Noise Power Supply Controller for Notebook Computers |
| SC1403 | 制造商:SEMTECH 制造商全稱:Semtech Corporation 功能描述:Mobile Multi-Output PWM Controller with Virtual Current SenseTM |
| SC1403_04 | 制造商:SEMTECH 制造商全稱:Semtech Corporation 功能描述:Mobile Multi-Output PWM Controller with Lossless Current Sense |
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