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参数资料
| 型号： | SP7661EB |
| 厂商： | Exar Corporation |
| 文件页数： | 10/20页 |
| 文件大小： | 0K |
| 描述： | EVAL BOARD FOR SP7661 |
| 标准包装： | 1 |
| 系列： | * |
APPLICATIONS INFORMATION
L =
V OUT ? (V IN(MAX) - V OUT )
=
I PP
V OUT ? (V IN(MAX) - V OUT )
I PEAK = I OUT(MAX) +
P L( C U ) = I L(RMS) ? R WINDING
√ ( )
I PP
I L(RMS) = I OUT(MAX) ?
+
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 SP7661 circuit, 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 inductor values pro -
vide 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
operating point determine the inductor value
as follows:
.
V IN(MAX) ? ? s ? K R ? I OUT(MAX)
where:
? 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:
.
V IN(MAX) ? ? s ?L
Once the required inductor value is selected,
the proper selection of core material is based
on peak inductor current and efficiency re -
quirements. 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
switching frequency. Low cost powdered-
iron cores have a gradual saturation char -
acteristic but can introduce considerable
AC core loss, especially when the induc -
tor value is relatively low and the ripple
current is high. Ferrite materials, although
more expensive, have an abrupt satura -
tion characteristic with the inductance
dropping sharply when the peak design
current is exceeded. Nevertheless, they
are preferred at high switching frequen -
cies 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 minimize 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 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 induc -
tor selection can affect the resulting power
supply efficiency by more than 15%!
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:
2
.
3 I OUT(MAX)
Mar -07 Rev N
SP766 Wide Input Voltage Range 3A, 600kHz Buck Regulator
0
? 2007 Sipex Corporation
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相关代理商/技术参数 |
参数描述 |
|---|---|
| SP7661ER | 制造商:SIPEX 制造商全称:Sipex Corporation 功能描述:Evaluation Board Manual |
| SP7661ER/TR | 制造商:SIPEX 制造商全称:Sipex Corporation 功能描述:Wide Input Voltage Range 3A, 600kHz, Buck Regulator |
| SP7661ER-L | 功能描述:开关变换器、稳压器与控制器 Buck Regulator 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 |
| SP7661ERL/TR | 制造商:SIPEX 制造商全称:Sipex Corporation 功能描述:Wide Input Voltage Range 3A, 600kHz, Buck Regulator |
| SP7661ER-L/TR | 功能描述:开关变换器、稳压器与控制器 WIDE INPUT VOLTAGE Range A600KHz 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 |
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