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参数资料
| 型号： | LM2679SD-12/NOPB |
| 厂商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分类： | 稳压器 |
| 英文描述： | 8.1 A SWITCHING REGULATOR, 280 kHz SWITCHING FREQ-MAX, DSO14 |
| 封装： | LLP-14 |
| 文件页数： | 6/26页 |
| 文件大小： | 672K |
| 代理商： | LM2679SD-12/NOPB |
Using Figure 6, the intersection of 27V
μS horizontally and
the 3.5A vertical line (I
load max) indicates that L48 , a 47μH
inductor, or L49, a 33
μH inductor could be used. Either in-
ductor will be suitable, but for this example selecting the larger
inductance will result in lower ripple current.
From Table 1, L48 in a surface mount component is available
from Pulse Engineering with part number P0848.
Step 4:
Use Table 6 to determine an output capacitor. With a
14.8V output the 12.5 to 15V row is used and with a 47
μH
inductor there are three surface mount output capacitor solu-
tions. Table 2 provides the actual capacitor characteristics
based on the C Code number. Any of the following choices
can be used:
1 x 33
μF/20V AVX TPS (code C6)
1 x 47
μF/20V Sprague 594 (code C8)
1 x 47
μF/20V Kemet T495 (code C8)
Important Note:
When using the adjustable device in low
voltage applications (less than 3V output), if the nomograph,
Figure 6, selects an inductance of 22
μH or less, Table 6 does
not provide an output capacitor solution. With these condi-
tions the number of output capacitors required for stable
operation becomes impractical. It is recommended to use ei-
ther a 33
μH or 47μH inductor and the output capacitors from
Table 6.
Step 5:
An input capacitor for this example will require at least
a 35V WV rating with an rms current rating of 1.75A (1/2 Iout
max). From Table 2 it can be seen that C12, a 33
μF/35V ca-
pacitor from Sprague, has the highest voltage/current rating
of the surface mount components and that two of these ca-
pacitor in parallel will be adquate.
Step 6:
From Table 5 a 5A or more Schottky diode must be
selected. For surface mount diodes with a margin of safety on
the voltage rating one of two diodes can be used:
MBRD1545CT
6TQ045S
Step 7:
A 0.01
μF capacitor will be used for Cboost.
The softstart pin will be left open circuited.
Step 8:
Determine a value for R
ADJ to provide a peak switch
current limit of at least 3.5A plus 50% or 5.25A.
Use a value of 7.15K
Ω.
LLP PACKAGE DEVICES
The LM2679 is offered in the 14 lead LLP surface mount
package to allow for a significantly decreased footprint with
equivalent power dissipation compared to the TO-263.
The Die Attach Pad (DAP) can and should be connected to
PCB Ground plane/island. For CAD and assembly guidelines
refer
to
Application
Note
AN-1187
at
http://
power.national.com.
www.national.com
14
LM2679
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LM2679SD-3.3 | 功能描述:直流/直流开关转换器 RoHS:否 制造商:STMicroelectronics 最大输入电压:4.5 V 开关频率:1.5 MHz 输出电压:4.6 V 输出电流:250 mA 输出端数量:2 最大工作温度:+ 85 C 安装风格:SMD/SMT |
| LM2679SD-3.3/NOPB | 功能描述:直流/直流开关转换器 RoHS:否 制造商:STMicroelectronics 最大输入电压:4.5 V 开关频率:1.5 MHz 输出电压:4.6 V 输出电流:250 mA 输出端数量:2 最大工作温度:+ 85 C 安装风格:SMD/SMT |
| LM2679SD-5.0 | 功能描述:直流/直流开关转换器 RoHS:否 制造商:STMicroelectronics 最大输入电压:4.5 V 开关频率:1.5 MHz 输出电压:4.6 V 输出电流:250 mA 输出端数量:2 最大工作温度:+ 85 C 安装风格:SMD/SMT |
| LM2679SD-5.0/NOPB | 功能描述:直流/直流开关转换器 RoHS:否 制造商:STMicroelectronics 最大输入电压:4.5 V 开关频率:1.5 MHz 输出电压:4.6 V 输出电流:250 mA 输出端数量:2 最大工作温度:+ 85 C 安装风格:SMD/SMT |
| LM2679SD-ADJ | 功能描述:直流/直流开关转换器 RoHS:否 制造商:STMicroelectronics 最大输入电压:4.5 V 开关频率:1.5 MHz 输出电压:4.6 V 输出电流:250 mA 输出端数量:2 最大工作温度:+ 85 C 安装风格:SMD/SMT |
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