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参数资料
| 型号： | SP7651EB |
| 厂商： | Exar Corporation |
| 文件页数： | 7/15页 |
| 文件大小： | 0K |
| 描述： | EVAL BOARD FOR SP7651 |
| 标准包装： | 1 |
| 系列： | * |
APPLICATIONS INFORMATION
L= V OUT (V IN ( MAX ) - V OUT )
I PEAK = I OUT ( MAX ) +
P L ( CU )=I L ( RMS ) R WINDING
V IN ( MAX ) F S L
( I )
I PP
3
InductorSelection
There are many factors to consider in se-
lecting the inductor, including: core material,
inductance vs. frequency, current handling
capability, efficiency, size and EMI. In a typi -
cal SP765 circuit, the inductor is chosen
primarily by operating frequency, saturation
current and DC resistance. Increasing the
inductor value will decrease output voltage
ripple, but degrade transient response. Low
inductor values provide the smallest size, but
cause large ripple currents, poor efficiency
and require more output capacitance to
smooth out the larger ripple current. The
inductor 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 com-
promise 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
operating point determine the inductor value
as follows:
V IN ( MAX ) F s Kr I OUT ( MAX )
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:
V OUT (V IN ( MAX ) - V OUT )
I PP =
Once the required inductor value is se-
lected, the proper selection of core mate-
rial is based on peak inductor current and
efficiency requirements. The core must be
large enough not to saturate at the peak
inductor current...
I PP
2
...and provide low core loss at the high switch-
ing frequency. Low cost powdered-iron cores
are inappropriate for 900kHz operation.
Gapped ferrite inductors are widely available
for consideration. Select devices that have
operating data shown up to MHz. Ferrite
materials, on the other hand, are more
expensive and have an abrupt saturation
characteristic with the inductance dropping
sharply when the peak design current is
exceeded. Nevertheless, they are preferred
at high switching frequencies because they
present very low core loss and the design
only needs to prevent saturation. In general,
ferrite or molypermalloy materials will be
used with the SP765 .
Optimizing Efficiency
The power dissipated in the inductor is equal
to the sum of the core and copper losses. To
minimize copper losses, the winding resis-
tance needs to be minimized, but this usu-
ally comes at the expense of using a larger
inductor. Core losses have a more significant
contribution at low output current where the
copper losses are at a minimum, and can
typically be neglected at higher output cur-
rents where the copper losses dominate.
Core loss information is usually available
from the magnetics vendor. Proper inductor
selection can affect the resulting power sup-
ply efficiency by more than 15-20%!
The copper loss in the inductor can be cal-
culated using the following equation:
2
where I L(RMS) is the RMS inductor current
that can be calculated as follows:
I L ( RMS )=I OUT ( MAX ) 1 + OUT ( MAX )
2
Rev J: 3/ 4/07
SP765 Wide Input Voltage Range 3A, 900kHz, Buck Regulator
7
? Copyright 2007 Sipex Corporation
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相关代理商/技术参数 |
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| SP7651ER | 制造商:SIPEX 制造商全称:Sipex Corporation 功能描述:Evaluation Board Manual |
| SP7651ER/TR | 制造商:SIPEX 制造商全称:Sipex Corporation 功能描述:Wide Input Voltage Range 3A, 900kHz, Buck Regulator |
| SP7651ER-L | 功能描述:DC/DC 开关控制器 Buck Regulator RoHS:否 制造商:Texas Instruments 输入电压:6 V to 100 V 开关频率: 输出电压:1.215 V to 80 V 输出电流:3.5 A 输出端数量:1 最大工作温度:+ 125 C 安装风格: 封装 / 箱体:CPAK |
| SP7651ER-L/TR | 功能描述:开关变换器、稳压器与控制器 WIDE INPUT VOLTAGE RANGE, 3A 900k RoHS:否 制造商:Texas Instruments 输出电压:1.2 V to 10 V 输出电流:300 mA 输出功率: 输入电压:3 V to 17 V 开关频率:1 MHz 工作温度范围: 安装风格:SMD/SMT 封装 / 箱体:WSON-8 封装:Reel |
| SP7652 | 制造商:SIPEX 制造商全称:Sipex Corporation 功能描述:Wide Input Voltage Range 6A, 600kHz, Buck Regulator |
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