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参数资料
| 型号： | SP7655EB |
| 厂商： | Exar Corporation |
| 文件页数： | 7/16页 |
| 文件大小： | 0K |
| 描述： | EVAL BOARD FOR SP7655 |
| 标准包装： | 1 |
| 系列： | * |
APPLICATIONS INFORMATION
Inductor Selection
There are many factors to consider in selecting
the inductor including core material, inductance
vs. frequency, current handling capability, effi-
I PEAK = I OUT (max) +
I PP
2
ciency, size and EMI. In a typical SP7655 cir-
cuit, the inductor is chosen primarily for value,
saturation current and DC resistance. Increasing
the inductor value will decrease output voltage
ripple, but degrade transient response. Low in-
ductor 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 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:
...and provide low core loss at the high switch-
ing frequency. Low cost powdered-iron cores
have a gradual saturation characteristic but can
introduce considerable AC core loss, especially
when the inductor value is relatively low and the
ripple current is high. Ferrite materials, although
more expensive, have an abrupt saturation char-
acteristic with the inductance dropping sharply
when the peak design current is exceeded. Nev-
ertheless, they are preferred at high switching
frequencies because they present very low core
loss while the designer is only required to
prevent saturation. In general, ferrite or
molypermalloy materials are a better choice for
all but the most cost sensitive applications.
Optimizing Efficiency
The power dissipated in the inductor is equal to
the sum of the core and copper losses. To mini-
L =
V OUT ( V IN (max) V OUT )
V IN (max) F S K r I OUT ( max)
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
where:
F S = switching frequency
K r = ratio of the AC inductor ripple current to
the maximum output current
The peak-to-peak inductor ripple current is:
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
magnetics vendor. Proper inductor selection can
affect the resulting power supply efficiency by
more than 15%!
The copper loss in the inductor can be calculated
I PP =
V OUT ( V IN (max) V OUT )
V I N (max) F S L
using the following equation:
P L ( Cu ) = I L 2 ( RMS ) R WINDING
( )
I L(RMS) = I OUT(max) 1 + 1
I PP
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...
where I L(RMS) is the RMS inductor current that
can be calculated as follows:
2
3 I OUT(max)
Rev E: 3/2 /07
SP7655 Wide Input Voltage Range 8A, 300kHz, Buck Regulator
7
? 2007 Sipex Corporation
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相关代理商/技术参数 |
参数描述 |
|---|---|
| SP7655ER | 制造商:SIPEX 制造商全称:Sipex Corporation 功能描述:Evaluation Board Manual |
| SP7655ER/TR | 制造商:SIPEX 制造商全称:Sipex Corporation 功能描述:Wide Input Voltage Range, 8Amp 300kHz, Buck Regulator |
| SP7655ERL | 制造商:SIPEX 制造商全称:Sipex Corporation 功能描述:Wide Input Voltage Range, 8Amp 300kHz, Buck Regulator |
| SP7655ER-L | 功能描述:线性稳压器 - 标准 Buck Regulator RoHS:否 制造商:STMicroelectronics 输出类型: 极性: 输出电压:1.8 V 输出电流:150 mA 负载调节: 最大输入电压:5.5 V 线路调整率: 最大工作温度:+ 125 C 安装风格:SMD/SMT 封装 / 箱体:SOT-323-5L |
| SP7655ERL/TR | 制造商:SIPEX 制造商全称:Sipex Corporation 功能描述:Wide Input Voltage Range, 8Amp 300kHz, Buck Regulator |
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