參數(shù)資料
型號(hào)： LM2672M-3.3
廠商： NATIONAL SEMICONDUCTOR CORP
元件分類： 穩(wěn)壓器
英文描述： SIMPLE SWITCHER Power Converter High Efficiency 1A Step-Down Voltage Regulator with Features
中文描述： 2.2 A SWITCHING REGULATOR, 275 kHz SWITCHING FREQ-MAX, PDSO8
封裝： 0.150 INCH, PLASTIC, SO-8
文件頁(yè)數(shù)： 20/25頁(yè)
文件大小： 895K
代理商： LM2672M-3.3
LM2672 Series Buck Regulator Design Procedure (Adjustable Output)
(Continued)
PROCEDURE (Adjustable Output Voltage Version)
5. Input Capacitor (C
IN
)
A low ESR aluminum or tantalum bypass capacitor is needed
between the input pin and ground to prevent large voltage
transients from appearing at the input. This capacitor should be
located close to the IC using short leads. In addition, the RMS
current rating of the input capacitor should be selected to be at
least
1
2
the DC load current. The capacitor manufacturer data
sheet must be checked to assure that this current rating is not
exceeded. The curves shown in
Figure 14
show typical RMS
current ratings for several different aluminum electrolytic
capacitor values. A parallel connection of two or more
capacitors may be required to increase the total minimum RMS
current rating to suit the application requirements.
For an aluminum electrolytic capacitor, the voltage rating should
be at least 1.25 times the maximum input voltage. Caution must
be exercised if solid tantalum capacitors are used. The tantalum
capacitor voltage rating should be twice the maximum input
voltage. The tables in
Figure 15
show the recommended
application voltage for AVX TPS and Sprague 594D tantalum
capacitors. It is also recommended that they be surge current
tested by the manufacturer. The TPS series available from AVX,
and the 593D and 594D series from Sprague are all surge
current tested. Another approach to minimize the surge current
stresses on the input capacitor is to add a small inductor in
series with the input supply line.
Use caution when using ceramic capacitors for input bypassing,
because it may cause severe ringing at the V
IN
pin.
6. Boost Capacitor (C
B
)
This capacitor develops the necessary voltage to turn the switch
gate on fully. All applications should use a 0.01 μF, 50V ceramic
capacitor.
If the soft-start and frequency synchronization features are
desired, look at steps 6 and 7 in the fixed output design
procedure.
EXAMPLE (Adjustable Output Voltage Version)
5. Input Capacitor (C
IN
)
The important parameters for the input capacitor are the input
voltage rating and the RMS current rating. With a maximum
input voltage of 28V, an aluminum electrolytic capacitor with a
voltage rating of at least 35V (1.25 x V
IN
) would be needed.
The RMS current rating requirement for the input capacitor in a
buck regulator is approximately
1
2
the DC load current. In this
example, with a 1A load, a capacitor with a RMS current rating
of at least 500 mA is needed. The curves shown in
Figure 14
can be used to select an appropriate input capacitor. From the
curves, locate the 35V line and note which capacitor values
have RMS current ratings greater than 500 mA.
For a through hole design, a 330 μF/35V electrolytic capacitor
(Panasonic HFQ series, Nichicon PL, Sanyo MV-GX series or
equivalent) would be adequate. Other types or other
manufacturers’ capacitors can be used provided the RMS ripple
current ratings are adequate. Additionally, for a complete
surface mount design, electrolytic capacitors such as the Sanyo
CV-C or CV-BS and the Nichicon WF or UR and the NIC
Components NACZ series could be considered.
For surface mount designs, solid tantalum capacitors can be
used, but caution must be exercised with regard to the capacitor
surge current rating and voltage rating. In this example,
checking
Figure 15
, and the Sprague 594D series datasheet, a
Sprague 594D 15 μF, 50V capacitor is adequate.
6. Boost Capacitor (C
B
)
For this application, and all applications, use a 0.01 μF, 50V
ceramic capacitor.
Case
Style
(Note 7)
SM and TH
SM and TH
SM and TH
SM and TH
SM and TH
SM and TH
SM and TH
SM and TH
SM and TH
SM and TH
TH
Output
Voltage (V)
1.21–2.50
2.50–3.75
3.75–5.0
5.0–6.25
6.25–7.5
7.5–10.0
10.0–12.5
12.5–15.0
15.0–20.0
20.0–30.0
30.0–37.0
Inductance (μH)
68
—
C1
C5
C6
C6
C12
C12
C17
C20
C22
C25
22
—
—
—
—
C8
C9
C14
C15
C18
C21
C23
33
—
—
—
C4
C4
C10
C11
C16
C19
C22
C24
47
—
—
C4
C7
C7
C11
C12
C17
C20
C22
C24
100
C1
C2
C6
C6
C6
C13
C13
C17
C20
C22
C25
150
C2
C3
C6
C6
C6
C13
C13
C17
C20
C22
C25
220
C3
C3
C6
C6
C6
C13
C13
C17
C20
C22
C25
Note 7:
SM - Surface Mount, TH - Through Hole
FIGURE 16. Capacitor Code Selection Guide
L
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相關(guān)PDF資料
PDF描述
LM2672M-5.0 SIMPLE SWITCHER Power Converter High Efficiency 1A Step-Down Voltage Regulator with Features
LM2672N-12 SIMPLE SWITCHER Power Converter High Efficiency 1A Step-Down Voltage Regulator with Features
LM2672N-ADJ SIMPLE SWITCHER Power Converter High Efficiency 1A Step-Down Voltage Regulator with Features
LM2672M-ADJ SIMPLE SWITCHER Power Converter High Efficiency 1A Step-Down Voltage Regulator with Features
LM2673S-12 SIMPLE SWITCHER 3A Step-Down Voltage Regulator with Adjustable Current Limit
相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
LM2672M-5.0 功能描述:直流/直流開(kāi)關(guān)轉(zhuǎn)換器 RoHS:否 制造商:STMicroelectronics 最大輸入電壓:4.5 V 開(kāi)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
LM2672M-5.0 制造商:Texas Instruments 功能描述:SWITCHING REG 1A 5.0V 2672 SOIC8
LM2672M-5.0/NOPB 功能描述:直流/直流開(kāi)關(guān)轉(zhuǎn)換器 HIGH EFF 1A STEP- DOWN VLTG REG RoHS:否 制造商:STMicroelectronics 最大輸入電壓:4.5 V 開(kāi)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
LM2672M-ADJ 功能描述:直流/直流開(kāi)關(guān)轉(zhuǎn)換器 RoHS:否 制造商:STMicroelectronics 最大輸入電壓:4.5 V 開(kāi)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
LM2672M-ADJ 制造商:Texas Instruments 功能描述:SWITCHING REG 1A ADJ 2672 SOIC8
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