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| 型号： | LM2574N-005G |
| 厂商： | ON Semiconductor |
| 文件页数： | 17/26页 |
| 文件大小： | 0K |
| 描述： | IC REG BUCK 5V 0.5A 8DIP |
| 产品变化通告： | Product Obsolescence 19/Dec/2008 |
| 标准包装： | 50 |
| 类型： | 降压（降压） |
| 输出类型： | 固定 |
| 输出数： | 1 |
| 输出电压： | 5V |
| 输入电压： | 4.75 V ~ 40 V |
| PWM 型： | 电压模式 |
| 频率 - 开关： | 52kHz |
| 电流 - 输出： | 500mA |
| 同步整流器： | 无 |
| 工作温度： | -40°C ~ 125°C |
| 安装类型： | 通孔 |
| 封装/外壳： | 8-DIP（0.300"，7.62mm） |
| 包装： | 管件 |
| 供应商设备封装： | 8-PDIP |
| 其它名称： | LM2574N-005G-ND LM2574N-005GOS |
LM2574, NCV2574
0A
0.5 A
Inductor
Current
Waveform
0A
0.5 A
Power
Switch
Current
Waveform
0A
HORIZONTAL TIME BASE: 5.0 m s/DIV
Figure 24. Continuous Mode Switching
Current Waveforms
Inductor 0.1 A
Current
Waveform 0 A
Power
Switch 0.1 A
Current
Waveform
HORIZONTAL TIME BASE: 5.0 m s/DIV
Figure 25. Discontinuous Mode Switching
Current Waveforms
GENERAL RECOMMENDATIONS
Output Voltage Ripple and Transients
Source of the Output Ripple
Since the LM2574 is a switch mode power supply
regulator, its output voltage, if left unfiltered, will contain a
sawtooth ripple voltage at the switching frequency. The
output ripple voltage value ranges from 0.5% to 3% of the
output voltage. It is caused mainly by the inductor sawtooth
ripple current multiplied by the ESR of the output capacitor.
Short Voltage Spikes and How to Reduce Them
The regulator output voltage may also contain short
voltage spikes at the peaks of the sawtooth waveform (see
Figure 26). These voltage spikes are present because of the
fast switching action of the output switch, and the parasitic
inductance of the output filter capacitor. There are some
other important factors such as wiring inductance, stray
capacitance, as well as the scope probe used to evaluate these
transients, all these contribute to the amplitude of these
spikes. To minimize these voltage spikes, low inductance
capacitors should be used, and their lead lengths must be
kept short. The importance of quality printed circuit board
layout design should also be highlighted.
Voltage spikes caused by switching action of the output
switch and the parasitic inductance of the output capacitor
Unfiltered
Output
Voltage
Filtered
Output
Voltage
HORIZONTAL TIME BASE: 5.0 m s/DIV
Minimizing the Output Ripple
In order to minimize the output ripple voltage it is possible
to enlarge the inductance value of the inductor L1 and/or to
use a larger value output capacitor. There is also another way
to smooth the output by means of an additional LC filter
(20 m H, 100 m F), that can be added to the output (see
Figure 35) to further reduce the amount of output ripple and
transients. With such a filter it is possible to reduce the
output ripple voltage transients 10 times or more. Figure 26
shows the difference between filtered and unfiltered output
waveforms of the regulator shown in Figure 34.
The upper waveform is from the normal unfiltered output
of the converter, while the lower waveform shows the output
ripple voltage filtered by an additional LC filter.
Heatsinking and Thermal Considerations
The LM2574 is available in both 8?pin DIP and SO?16L
packages. When used in the typical application the copper lead
frame conducts the majority of the heat from the die, through
the leads, to the printed circuit copper. The copper and the
board are the heatsink for this package and the other heat
producing components, such as the catch diode and inductor.
For the best thermal performance, wide copper traces
should be used and all ground and unused pins should be
soldered to generous amounts of printed circuit board
copper, such as a ground plane. Large areas of copper
provide the best transfer of heat to the surrounding air. One
exception to this is the output (switch) pin, which should not
have large areas of copper in order to minimize coupling to
sensitive circuitry.
Additional improvement in heat dissipation can be
achieved even by using of double sided or multilayer boards
which can provide even better heat path to the ambient.
Using a socket for the 8?pin DIP package is not
recommended because socket represents an additional
thermal resistance, and as a result the junction temperature
will be higher.
Figure 26. Output Ripple Voltage Waveforms
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LM2574N-012 | 功能描述:直流/直流开关调节器 12V 500mA Buck PWM RoHS:否 制造商:International Rectifier 最大输入电压:21 V 开关频率:1.5 MHz 输出电压:0.5 V to 0.86 V 输出电流:4 A 输出端数量: 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:PQFN 4 x 5 |
| LM2574N-012G | 功能描述:直流/直流开关转换器 12V 500mA Buck PWM 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 |
| LM2574N-015 | 功能描述:直流/直流开关调节器 15V 500mA Buck PWM RoHS:否 制造商:International Rectifier 最大输入电压:21 V 开关频率:1.5 MHz 输出电压:0.5 V to 0.86 V 输出电流:4 A 输出端数量: 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:PQFN 4 x 5 |
| LM2574N-015G | 功能描述:直流/直流开关调节器 15V 500mA Buck PWM RoHS:否 制造商:International Rectifier 最大输入电压:21 V 开关频率:1.5 MHz 输出电压:0.5 V to 0.86 V 输出电流:4 A 输出端数量: 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:PQFN 4 x 5 |
| LM2574N-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 |
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