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參數(shù)資料
| 型號(hào)： | FAN53168 |
| 廠商： | Fairchild Semiconductor Corporation |
| 英文描述： | 6-Bit VID Controlled 2-4 Phase DC-DC Controller |
| 中文描述： | 6位VID控制2-4相DC - DC控制器 |
| 文件頁數(shù)： | 17/28頁 |
| 文件大?。?/td> | 397K |
| 代理商： | FAN53168 |
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PRODUCT SPECIFICATION
FAN53168
REV. 1.0.0 6/9/03
17
Where t
SS
is the desired soft-start time. Assuming an R
DLY
of
301k
and a desired soft-start time of 3ms, C
DLY
is 35nF. A close
standard value for C
DLY
is 47nF. Once C
DLY
has been chosen,
R
DLY
can be calculated for the current limit latch-off time using:
If the result for R
DLY
is less than 200k
, then a smaller soft-
start time should be considered by recalculating the equation
for C
DLY
or a longer latch-off time should be used. In no
case should R
DLY
be less than 200k
. In this example, a
delay time of 8ms gives R
DLY
= 334k
. A close standard 1%
value is 301k
.
Inductor Selection
The choice of inductance for the inductor determines the
ripple current in the inductor. Less inductance leads to more
ripple current, which increases the output ripple voltage and
conduction losses in the MOSFETs, but allows using
smaller-size inductors and, for a speci
fi
ed peak-to-peak
transient deviation, less total output capacitance. Conversely,
a higher inductance means lower ripple current and reduced
conduction losses, but requires larger-size inductors and
more output capacitance for the same peak-to-peak transient
deviation. In any multi-phase converter, a practical value for
the peak-to-peak inductor ripple current is less than 50% of
the maximum DC current in the same inductor. Equation 4
shows the relationship between the inductance, oscillator
frequency, and peak-to-peak ripple current in the inductor.
Equation 5 can be used to determine the minimum induc-
tance based on a given output ripple voltage:
Solving Equation 5 for a 10 mV
p-p
output ripple voltage
yields:
If the ripple voltage ends up less than that designed for, the
inductor can be made smaller until the ripple value is met.
This will allow optimal transient response and minimum
output decoupling.
The smallest possible inductor should be used to minimize
the number of output capacitors. Choosing a 650nH inductor
is a good choice for a starting point and gives a calculated
ripple current of 8.86A. The inductor should not saturate at
the peak current of 26.1A and should be able to handle the
sum of the power dissipation caused by the average current
of 21.7A in the winding and core loss.
Another important factor in the inductor design is the DCR,
which is used for measuring the phase currents. A large DCR
will cause excessive power losses, while too small a value
will lead to increased measurement error. A good rule of
thumb is to have the DCR be about 1 to 1.5 times the droop
resistance (R
O
). For our example, we are using an inductor
with a DCR of 1.6 m
.
Designing an Inductor
Once the inductance and DCR are known, the next step is
either to design an inductor or
fi
nd a standard inductor that
comes as close as possible to meeting the overall design
goals. It is also important to have the inductance and DCR
tolerance speci
fi
ed to keep the accuracy of the system
controlled. Using 15% for the inductance and 8% for the
DCR (at room temperature) are reasonable tolerances that
most manufacturers can meet.
The first decision in designing the inductor is to choose the
core material. There are several possibilities for providing
low core loss at high frequencies. Two examples are the
powder cores (e.g., Kool-M
μ
from Magnetics, Inc. or
Micrometals) and the gapped soft ferrite cores (e.g., 3F3
or 3F4 from Philips). Low frequency powdered iron cores
should be avoided due to their high core loss, especially
when the inductor value is relatively low and the ripple
current is high.
The best choice for a core geometry is a closed-loop types,
such as pot cores, PQ, U, and E cores, or toroids. A good
compromise between price and performance are cores with a
toroidal shape.
There are many useful references for quickly designing a
power inductor, such as:
Magnetics Design References
1.
Magnetic Designer Software
Intusoft (www.intusoft.com)
2.
Designing Magnetic Components for High-Frequency
DC-DC Converters
, by William T. McLyman, Kg Mag-
netics, Inc. ISBN 1883107008
Selecting a Standard Inductor
The companies listed below can provide design consultation
and deliver power inductors optimized for high power appli-
cations upon request.
Power Inductor Manufacturers
Coilcraft
(847) 639-6400
www.coilcraft.com
Coiltronics
(561) 752-5000
www.coiltronics.com
R
DLY
1.96
------------------------------------
t
DLY
×
=
(3)
I
R
V
--------------------------------
1
D
–
(
)
×
SW
=
(4)
L
V
-----------------------------------------–
R
×
f
SW
)
)
V
RIPPLE
≥
(5)
L
--------------------------------------------------–
)
≥
534nH
=
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| FAN53168MTC | 制造商:FAIRCHILD 制造商全稱:Fairchild Semiconductor 功能描述:6-Bit VID Controlled 2-4 Phase DC-DC Controller |
| FAN53168MTCX | 功能描述:DC/DC 開關(guān)控制器 Buck Controller 2to4 Phs VID Sync RoHS:否 制造商:Texas Instruments 輸入電壓:6 V to 100 V 開關(guān)頻率: 輸出電壓:1.215 V to 80 V 輸出電流:3.5 A 輸出端數(shù)量:1 最大工作溫度:+ 125 C 安裝風(fēng)格: 封裝 / 箱體:CPAK |
| FAN53180 | 制造商:FAIRCHILD 制造商全稱:Fairchild Semiconductor 功能描述:6-Bit VID Controlled 2-4 Phase DC-DC Controller |
| FAN53180MTC | 制造商:FAIRCHILD 制造商全稱:Fairchild Semiconductor 功能描述:6-Bit VID Controlled 2-4 Phase DC-DC Controller |
| FAN53180MTCX | 功能描述:DC/DC 開關(guān)控制器 Buck Controller 2to4 Phs VID Sync RoHS:否 制造商:Texas Instruments 輸入電壓:6 V to 100 V 開關(guān)頻率: 輸出電壓:1.215 V to 80 V 輸出電流:3.5 A 輸出端數(shù)量:1 最大工作溫度:+ 125 C 安裝風(fēng)格: 封裝 / 箱體:CPAK |
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