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参数资料
| 型号： | LM2576 |
| 厂商： | ON SEMICONDUCTOR |
| 英文描述： | 3.0 A, 15 V, Step-Down Switching Regulator(3.0A,15V,降压型开关稳压器) |
| 中文描述： | 3.0甲，15 V的，降压型开关稳压器（3.0A的，15V的，降压型开关稳压器） |
| 文件页数： | 9/28页 |
| 文件大小： | 275K |
| 代理商： | LM2576 |
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LM2576
http://onsemi.com
17
When multiple switching regulators are located on the
same printed circuit board, open core magnetics can cause
interference between two or more of the regulator circuits,
especially at high currents due to mutual coupling. A toroid,
pot core or Ecore (closed magnetic structure) should be
used in such applications.
Do Not Operate an Inductor Beyond its
Maximum Rated Current
Exceeding an inductor’s maximum current rating may
cause the inductor to overheat because of the copper wire
losses, or the core may saturate. Core saturation occurs when
the flux density is too high and consequently the cross
sectional area of the core can no longer support additional
lines of magnetic flux.
This causes the permeability of the core to drop, the
inductance value decreases rapidly and the inductor begins
to look mainly resistive. It has only the DC resistance of the
winding. This can cause the switch current to rise very
rapidly and force the LM2576 internal switch into
cyclebycycle current limit, thus reducing the DC output
load current. This can also result in overheating of the
inductor and/or the LM2576. Different inductor types have
different saturation characteristics, and this should be kept
in mind when selecting an inductor.
0.4 A
0 A
0.4 A
0 A
Inductor
Current
Waveform
Power
Switch
Current
Waveform
Figure 24. Discontinuous Mode Switching Current
Waveforms
VER
TICAL
RESOLUTION
200
mA/DIV
HORIZONTAL TIME BASE: 5.0
ms/DIV
GENERAL RECOMMENDATIONS
Output Voltage Ripple and Transients
Source of the Output Ripple
Since the LM2576 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 25). 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.
Unfiltered
Output
Voltage
Filtered
Output
Voltage
HORIZONTAL TIME BASE: 5.0
ms/DIV
Figure 25. Output Ripple Voltage Waveforms
VER
TRICAL
Voltage spikes
caused by
switching action
of the output
switch and the
parasitic
inductance of the
output capacitor
RESOLUTION
20
mV/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
mH, 100 mF), that can be added to the output (see Figure 34)
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 25 shows the
difference between filtered and unfiltered output waveforms
of the regulator shown in Figure 34.
The lower waveform is from the normal unfiltered output
of the converter, while the upper waveform shows the output
ripple voltage filtered by an additional LC filter.
Heatsinking and Thermal Considerations
The ThroughHole Package TO220
The LM2576 is available in two packages, a 5pin
TO220(T, TV) and a 5pin surface mount D2PAK(D2T).
Although the TO220(T) package needs a heatsink under
most conditions, there are some applications that require no
heatsink to keep the LM2576 junction temperature within
the allowed operating range. Higher ambient temperatures
require some heat sinking, either to the printed circuit (PC)
board or an external heatsink.
The Surface Mount Package D2PAK and its
Heatsinking
The other type of package, the surface mount D2PAK, is
designed to be soldered to the copper on the PC board. The
copper and the board are the heatsink for this package and
the other heat producing components, such as the catch
diode and inductor. The PC board copper area that the
package is soldered to should be at least 0.4 in2 (or 260 mm2)
and ideally should have 2 or more square inches (1300 mm2)
of 0.0028 inch copper. Additional increases of copper area
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LM2576/D | 制造商:未知厂家 制造商全称:未知厂家 功能描述:Easy Switcher? 3.0 A Step-Down Voltage Regulator |
| LM2576_05 | 制造商:MICREL 制造商全称:Micrel Semiconductor 功能描述:52kHz Simple 3A Buck Regulator |
| LM2576_06 | 制造商:ONSEMI 制造商全称:ON Semiconductor 功能描述:3.0 A, 15 V, Step−Down Switching Regulator |
| LM2576_11 | 制造商:HTC 制造商全称:HTC Korea TAEJIN Technology Co. 功能描述:3A, 52kHz, Step-Down Switching Regulator |
| LM2576_12 | 制造商:MOTOROLA 制造商全称:Motorola, Inc 功能描述:EASY SWITCHERER 3.0 A STEPa??DOWN VOLTAGE REGULATOR |
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