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參數(shù)資料
| 型號： | LM2673T-ADJ |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | SIMPLE SWITCHER 3A Step-Down Voltage Regulator with Adjustable Current Limit |
| 中文描述： | 5.4 A SWITCHING REGULATOR, 280 kHz SWITCHING FREQ-MAX, ZFM7 |
| 封裝： | TO-220, 7 PIN |
| 文件頁數(shù)： | 14/26頁 |
| 文件大?。?/td> | 451K |
| 代理商： | LM2673T-ADJ |
Application Hints
(Continued)
The switching frequency of 260KHz is the nominal value to
use to estimate the ON time of the switch during which
energy is stored in the inductor.
For this example E
T is found to be:
Using
Figure 6
, the intersection of 27V
μS horizontally and
the 2A vertical line (I
max) indicates that L38 , a 68μH
inductor, should be used.
From Table 1, L38 in a surface mount component is available
from Pulse Engineering with part number PE-54038S.
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 68μH
inductor there are three surface mount output capacitor so-
lutions. Table 2 provides the actual capacitor characteristics
based on the C Code number. Any of the following choices
can be used:
1 x 33μF/20V AVX TPS (code C6)
1 x 47μF/20V Sprague 594 (code C8)
1 x 47μF/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 22μH 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
either a 33μH 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 1A (1/2
Iout max). From Table 2 it can be seen that C12, a 33μF/35V
capacitor from Sprague, has the required voltage/current
rating of the surface mount components.
Step 6:
From Table 5 a 3A Schottky diode must be selected.
For surface mount diodes with a margin of safety on the
voltage rating one of five diodes can be used:
SK34
30BQ040
30WQ04F
MBRS340
MBRD340
Step 7:
A 0.01μF capacitor will be used for Cboost.
The softstart pin will be left open circuited.
Step 8:
Determine a value for R
to provide a peak switch
current limit of at least 2A plus 50% or 3A.
Use a value of 12.4K
.
LLP PACKAGE DEVICES
The LM2673 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. For
details on mounting and soldering specifications, refer to
Application Note AN-1187.
L
www.national.com
14
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相關代理商/技術參數(shù) |
參數(shù)描述 |
|---|---|
| LM2673T-ADJ | 制造商:Texas Instruments 功能描述:SWITCHING REG 3A ADJ 2673 TO2207 |
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| LM2674 | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:SIMPLE SWITCHER Power Converter High Efficiency 500 mA Step-Down Voltage Regulator |
| LM2674LD-12 | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:SIMPLE SWITCHER Power Converter High Efficiency 500 mA Step-Down Voltage Regulator |
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