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參數(shù)資料
| 型號： | LM2674LDX-5.0 |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | SIMPLE SWITCHER Power Converter High Efficiency 500 mA Step-Down Voltage Regulator |
| 中文描述： | 1.25 A SWITCHING REGULATOR, 275 kHz SWITCHING FREQ-MAX, DSO16 |
| 封裝： | LLP-16 |
| 文件頁數(shù)： | 18/26頁 |
| 文件大?。?/td> | 947K |
| 代理商： | LM2674LDX-5.0 |
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LM2674 Series Buck Regulator Design Procedure (Adjustable Output)
PROCEDURE (Adjustable Output Voltage Version)
To simplify the buck regulator design procedure, National
Semiconductor is making available computer design software to
be used with the
SIMPLE SWITCHER
line of switching
regulators.
LM267X Made Simple
(version 6.0)
is available for
use on
Windows
3.1, NT, or 95 operating systems.
Given:
V
OUT
= Regulated Output Voltage
V
IN
(max) = Maximum Input Voltage
I
LOAD
(max) = Maximum Load Current
F = Switching Frequency
(Fixed at a nominal 260 kHz).
1. Programming Output Voltage
(Selecting R
1
and R
2
, as
shown in
Figure 3
)
Use the following formula to select the appropriate resistor
values.
EXAMPLE (Adjustable Output Voltage Version)
Given:
V
OUT
= 20V
V
IN
(max) = 28V
I
LOAD
(max) = 500 mA
F = Switching Frequency
(Fixed at a nominal 260 kHz).
1. Programming Output Voltage
(Selecting R
1
and R
2
, as
shown in
Figure 3
)
Select R
1
to be 1 k
, 1%. Solve for R
2
.
where V
REF
= 1.21V
Select a value for R
1
between 240
and 1.5 k
. The lower
resistor values minimize noise pickup in the sensitive feedback
pin. (For the lowest temperature coefficient and the best stability
with time, use 1% metal film resistors.)
R
2
= 1k (16.53 1) = 15.53 k
, closest 1% value is 15.4 k
.
R
2
= 15.4 k
.
2. Inductor Selection (L1)
A.
Calculate the inductor Volt
microsecond constant E
T (V
μs), from the following formula:
2. Inductor Selection (L1)
A.
Calculate the inductor Volt
microsecond constant (E
T),
where V
SAT
=internal switch saturation voltage=0.25V and V
D
=
diode forward voltage drop = 0.5V
B.
Use the E
T value from the previous formula and match it
with the E
T number on the vertical axis of the Inductor Value
Selection Guide shown in
Figure 7
.
C.
On the horizontal axis, select the maximum load current.
D.
Identify the inductance region intersected by the E
T value
and the Maximum Load Current value. Each region is identified
by an inductance value and an inductor code (LXX).
B.
E
T = 21.6 (V
μs)
C.
I
LOAD
(max) = 500 mA
D.
From the inductor value selection guide shown in
Figure 7
,
the inductance region intersected by the 21.6 (V
μs) horizontal
line and the 500mA vertical line is 100 μH, and the inductor
code is L20.
E.
From the table in
Figure 8
, locate line L20, and select an
inductor part number from the list of manufacturers part
numbers.
E.
Select an appropriate inductor from the four manufacturer’s
part numbers listed in
Figure 8
. For information on the different
types of inductors, see the inductor selection in the fixed output
voltage design procedure.
3. Output Capacitor Selection (C
OUT
)
A.
Select an output capacitor from the capacitor code selection
guide in
Figure 16
. Using the inductance value found in the
inductor selection guide, step 1, locate the appropriate capacitor
code corresponding to the desired output voltage.
3. Output Capacitor SeIection (C
OUT
)
A.
Use the appropriate row of the capacitor code selection
guide, in
Figure 16
. For this example, use the 15–20V row. The
capacitor code corresponding to an inductance of 100 μH is
C20.
L
www.national.com
18
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| LM2674LDX-ADJ | SIMPLE SWITCHER Power Converter High Efficiency 500 mA Step-Down Voltage Regulator |
| LM2674M-5.0 | SIMPLE SWITCHER Power Converter High Efficiency 500 mA Step-Down Voltage Regulator |
| LM2674N-5.0 | SIMPLE SWITCHER Power Converter High Efficiency 500 mA Step-Down Voltage Regulator |
| LM2674N-ADJ | SIMPLE SWITCHER Power Converter High Efficiency 500 mA Step-Down Voltage Regulator |
| LM2674LDX-12 | SIMPLE SWITCHER Power Converter High Efficiency 500 mA Step-Down Voltage Regulator |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LM2674LDX-ADJ | 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 |
| LM2674M-12 | 功能描述:直流/直流開關(guān)轉(zhuǎn)換器 RoHS:否 制造商:STMicroelectronics 最大輸入電壓:4.5 V 開關(guān)頻率:1.5 MHz 輸出電壓:4.6 V 輸出電流:250 mA 輸出端數(shù)量:2 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT |
| LM2674M-12/NOPB | 功能描述:直流/直流開關(guān)轉(zhuǎn)換器 PWR CONVERTER HI EFF 500MA SD VLTG REG RoHS:否 制造商:STMicroelectronics 最大輸入電壓:4.5 V 開關(guān)頻率:1.5 MHz 輸出電壓:4.6 V 輸出電流:250 mA 輸出端數(shù)量:2 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT |
| LM2674M-12/NOPB | 制造商:Texas Instruments 功能描述:DC/DC Converter (DC-DC) / Switching Regu |
| LM2674M-3.3 | 功能描述:直流/直流開關(guān)轉(zhuǎn)換器 RoHS:否 制造商:STMicroelectronics 最大輸入電壓:4.5 V 開關(guān)頻率:1.5 MHz 輸出電壓:4.6 V 輸出電流:250 mA 輸出端數(shù)量:2 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT |
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