- 您现在的位置：买卖IC网 > PDF目录44550 > LM2675M-5.0EP (NATIONAL SEMICONDUCTOR CORP) 2.2 A SWITCHING REGULATOR, 275 kHz SWITCHING FREQ-MAX, PDSO8 PDF资料下载
参数资料
| 型号： | LM2675M-5.0EP |
| 厂商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分类： | 稳压器 |
| 英文描述： | 2.2 A SWITCHING REGULATOR, 275 kHz SWITCHING FREQ-MAX, PDSO8 |
| 封装： | 0.150 INCH |
| 文件页数： | 11/25页 |
| 文件大小： | 516K |
| 代理商： | LM2675M-5.0EP |
LM2675EP Series Buck Regulator Design Procedure (Adjustable Output)
(Continued)
PROCEDURE (Adjustable Output Voltage Version)
EXAMPLE (Adjustable Output Voltage Version)
4. Catch Diode Selection (D1)
A. In normal operation, the average current of the catch diode is
the load current times the catch diode duty cycle, 1-D (D is the
switch duty cycle, which is approximately V
OUT/VIN). The largest
value of the catch diode average current occurs at the maximum
input voltage (minimum D). For normal operation, the catch
diode current rating must be at least 1.3 times greater than its
maximum average current. However, if the power supply design
must withstand a continuous output short, the diode should have
a current rating greater than the maximum current limit of the
LM2675EP. The most stressful condition for this diode is a
shorted output condition.
4. Catch Diode Selection (D1)
A. Refer to the table shown in Figure 12. Schottky diodes
provide the best performance, and in this example a 1A, 40V
Schottky diode would be a good choice. If the circuit must
withstand a continuous shorted output, a higher current (at least
2.2A) Schottky diode is recommended.
B. The reverse voltage rating of the diode should be at least
1.25 times the maximum input voltage.
C. Because of their fast switching speed and low forward
voltage drop, Schottky diodes provide the best performance and
efficiency. The Schottky diode must be located close to the
LM2675EP using short leads and short printed circuit traces.
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 12 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.
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 12 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 F/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 F, 50V capacitor is adequate.
6. Boost Capacitor (C
B)
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 F, 50V ceramic
capacitor.
For this application, and all applications, use a 0.01 F, 50V
ceramic capacitor.
LM2675EP
Enhanced
Plastic
www.national.com
19
相关PDF资料 |
PDF描述 |
|---|---|
| LM2675LD-ADJEP | 2.2 A SWITCHING REGULATOR, 275 kHz SWITCHING FREQ-MAX, DSO8 |
| LM2675M-ADJEP | 2.2 A SWITCHING REGULATOR, 275 kHz SWITCHING FREQ-MAX, PDSO8 |
| LM2675LD-12EP | 2.2 A SWITCHING REGULATOR, 275 kHz SWITCHING FREQ-MAX, DSO8 |
| LM2675MX-5.0EP | 2.2 A SWITCHING REGULATOR, 275 kHz SWITCHING FREQ-MAX, PDSO8 |
| LM2675LD-3.3EP | 2.2 A SWITCHING REGULATOR, 275 kHz SWITCHING FREQ-MAX, DSO8 |
相关代理商/技术参数 |
参数描述 |
|---|---|
| LM2675M-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 |
| LM2675M-ADJ | 制造商:Texas Instruments 功能描述:SWITCHING REG 0.1A ADJ SMD 2675 |
| LM2675M-ADJ/NOPB | 功能描述:直流/直流开关转换器 HIGH EFF 1A STEP- DOWN VLTG REG 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 |
| LM2675M-ADJ/NOPB | 制造商:Texas Instruments 功能描述:DC/DC Converter (DC-DC) / Switching Regu |
| LM2675MX-12 | 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 |
发布紧急采购，3分钟左右您将得到回复。