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參數(shù)資料
| 型號： | LM2574 |
| 廠商： | ON SEMICONDUCTOR |
| 英文描述： | 0.5 A, Adjustable Output Voltage, Step-Down Switching Regulator(0.5A,可調(diào)輸出電壓,降壓型開關(guān)穩(wěn)壓器) |
| 中文描述： | 0.5甲，可調(diào)輸出電壓，降壓型開關(guān)穩(wěn)壓器（0.5A的，可調(diào)輸出電壓，降壓型開關(guān)穩(wěn)壓器） |
| 文件頁數(shù)： | 17/26頁 |
| 文件大?。?/td> | 295K |
| 代理商： | LM2574 |
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LM2574, NCV2574
http://onsemi.com
17
HORIZONTAL TIME BASE: 5.0 s/DIV
Figure 24. Continuous Mode Switching
Current Waveforms
V
0.5 A
0 A
0.5 A
0 A
Power
Switch
Current
Waveform
Inductor
Current
Waveform
V
HORIZONTAL TIME BASE: 5.0 s/DIV
Figure 25. Discontinuous Mode Switching
Current Waveforms
0.1 A
0 A
0.1 A
0 A
Power
Switch
Current
Waveform
Inductor
Current
Waveform
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.
HORIZONTAL TIME BASE: 5.0 s/DIV
V
Voltage spikes caused by switching action of the output
switch and the parasitic inductance of the output capacitor
Figure 26. Output Ripple Voltage Waveforms
Unfiltered
Output
Voltage
Filtered
Output
Voltage
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
H, 100 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 8pin DIP and SO16L
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 8pin DIP package is not
recommended because socket represents an additional
thermal resistance, and as a result the junction temperature
will be higher.
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| LM2575T-12 | EASY SWITCHERE⑩ 1.0 A STEP-DOWN VOLTAGE REGULATOR |
| LM2575D2T-15 | EASY SWITCHERE⑩ 1.0 A STEP-DOWN VOLTAGE REGULATOR |
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LM2574 3.3V WAF | 制造商:Motorola Inc 功能描述: |
| LM2574/D | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:Easy Switcher? 0.5A Step-Down Voltage Regulator |
| LM2574_05 | 制造商:MICREL 制造商全稱:Micrel Semiconductor 功能描述:52kHz Simple 0.5A Buck Regulator |
| LM2574_06 | 制造商:ONSEMI 制造商全稱:ON Semiconductor 功能描述:0.5 A, Adjustable Output Voltage, Step−Down Switching Regulator |
| LM2574-12 | 制造商:Texas Instruments 功能描述: |
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