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| 型號： | SP7651 |
| 英文描述： | Wide Input Voltage Range 3A, 900kHz, Buck Regulator |
| 中文描述： | 寬輸入電壓范圍第3A，900kHz的，降壓穩(wěn)壓器 |
| 文件頁數(shù)： | 7/12頁 |
| 文件大?。?/td> | 117K |
| 代理商： | SP7651 |
7
Date: 08/25/04
SP7651 Wide Input Voltage Range 3A, 900kHz, Buck Regulator Copyright 2004 Sipex Corporation
APPLICATIONS INFORMATION
Inductor Selection
There are many factors to consider in selecting
the inductor including core material, inductance
vs. frequency, current handling capability, effi-
ciency, size and EMI. In a typical SP7651 cir-
cuit, the inductor is chosen primarily by operat-
ing frequency, saturation current and DC resis-
tance. Increasing the inductor value will de-
crease output voltage ripple, but degrade tran-
sient response. Low inductor values provide the
smallest size, but cause large ripple currents,
poor efficiency and more output capacitance to
smooth out the larger ripple current. The induc-
tor must be able to handle the peak current at the
switching frequency without saturating, and the
copper resistance in the winding should be kept
as low as possible to minimize resistive power
loss. A good compromise between size, loss and
cost is to set the inductor ripple current to be
within 20% to 40% of the maximum output
current.
The switching frequency and the inductor oper-
ating point determine the inductor value as fol-
lows:
(max)
(max)
(max)
K
)
(
OUT
r
S
IN
OUT
IN
F
OUT
I
V
V
V
V
L
=
where:
Fs = switching frequency
Kr = ratio of the ac inductor ripple current to the
maximum output current
The peak to peak inductor ripple current is:
L
F
V
V
V
(
V
I
S
IN
OUT
IN
OUT
PP
(max)
(max)
)
=
Once the required inductor value is selected, the
proper selection of core material is based on
peak inductor current and efficiency require-
ments. The core must be large enough not to
saturate at the peak inductor current
2
(max)
PP
OUT
PEAK
I
I
I
+
=
and provide low core loss at the high switching
frequency. Low cost powdered iron cores are
inappropriate for 900kHz operation. Gapped
ferrite inductors are widely available for consid-
eration. Select devices that have operating data
shown up to 1MHz. Ferrite materials, on the
other hand, are more expensive and have an
abrupt saturation characteristic with the induc-
tance dropping sharply when the peak design
current is exceeded. Nevertheless, they are pre-
ferred at high switching frequencies because
they present very low core loss and the design
only needs to prevent saturation. In general,
ferrite or molyperm alloy materials will be used
with the SP7651.
Optimizing Efficiency
The power dissipated in the inductor is equal to
the sum of the core and copper losses. To mini-
mize copper losses, the winding resistance needs
to be minimized, but this usually comes at the
expense of a larger inductor. Core losses have a
more significant contribution at low output cur-
rent where the copper losses are at a minimum,
and can typically be neglected at higher output
currents where the copper losses dominate. Core
loss information is usually available from the
magnetic vendor. Proper inductor selection can
affect the resulting power supply efficiency by
more than 15-20%!
The copper loss in the inductor can be calculated
using the following equation:
I
P
(
)
(
=
WINDING
R
RMS
L
Cu
L
2
)
where
I
L(RMS)
is the RMS inductor current that
can be calculated as follows:
I
L(RMS)
= I
OUT(max)
1 + 1
(
I
PP
)
2
3 I
OUT(max)
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| SP7652 | Wide Input Voltage Range 6A, 600kHz, Buck Regulator |
| SP7652EB | Evaluation Board Manual |
| SP7652EU | Evaluation Board Manual |
| SP7653 | Wide Input Voltage Range, 1.3MHz,Buck Regulator |
| SP7653ER | Wide Input Voltage Range, 1.3MHz,Buck Regulator |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| SP7651_06 | 制造商:SIPEX 制造商全稱:Sipex Corporation 功能描述:Evaluation Board Manual |
| SP7651_07 | 制造商:SIPEX 制造商全稱:Sipex Corporation 功能描述:Wide Input Voltage Range 3Amp 900kHz Buck Regulator |
| SP7651EB | 功能描述:電源管理IC開發(fā)工具 Wide In Volt Range 3A 900kHz Buck Reg RoHS:否 制造商:Maxim Integrated 產(chǎn)品:Evaluation Kits 類型:Battery Management 工具用于評估:MAX17710GB 輸入電壓: 輸出電壓:1.8 V |
| SP7651ER | 制造商:SIPEX 制造商全稱:Sipex Corporation 功能描述:Evaluation Board Manual |
| SP7651ER/TR | 制造商:SIPEX 制造商全稱:Sipex Corporation 功能描述:Wide Input Voltage Range 3A, 900kHz, Buck Regulator |
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