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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： | 11/28页 |
| 文件大小： | 275K |
| 代理商： | LM2576 |
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LM2576
http://onsemi.com
19
This circuit configuration is able to deliver approximately
0.7 A to the output when the input voltage is 12 V or higher.
At lighter loads the minimum input voltage required drops
to approximately 4.7 V, because the buckboost regulator
topology can produce an output voltage that, in its absolute
value, is either greater or less than the input voltage.
Since the switch currents in this buckboost configuration
are higher than in the standard buck converter topology, the
available output current is lower.
This type of buckboost inverting regulator can also
require a larger amount of startup input current, even for
light loads. This may overload an input power source with
a current limit less than 5.0 A.
Such an amount of input startup current is needed for at
least 2.0 ms or more. The actual time depends on the output
voltage and size of the output capacitor.
Because of the relatively high startup currents required by
this inverting regulator topology, the use of a delayed startup
or an undervoltage lockout circuit is recommended.
Using a delayed startup arrangement, the input capacitor
can charge up to a higher voltage before the switchmode
regulator begins to operate.
The high input current needed for startup is now partially
supplied by the input capacitor Cin.
It has been already mentioned above, that in some
situations, the delayed startup or the undervoltage lockout
features could be very useful. A delayed startup circuit
applied to a buckboost converter is shown in Figure 27,
Figure 33 in the “Undervoltage Lockout” section describes
an undervoltage lockout feature for the same converter
topology.
Design Recommendations:
The inverting regulator operates in a different manner
than the buck converter and so a different design procedure
has to be used to select the inductor L1 or the output
capacitor Cout.
The output capacitor values must be larger than what is
normally required for buck converter designs. Low input
voltages or high output currents require a large value output
capacitor (in the range of thousands of
mF).
The recommended range of inductor values for the
inverting converter design is between 68
mH and 220 mH. To
select an inductor with an appropriate current rating, the
inductor peak current has to be calculated.
The following formula is used to obtain the peak inductor
current:
where ton +
|V
O
|
V
in )
|V
O
|
x
1.0
fosc
, and fosc + 52 kHz.
I
peak [
I
Load
(V
in )
|V
O
|)
V
in
)
V
in
xton
2L
1
Under normal continuous inductor current operating
conditions, the worst case occurs when Vin is minimal.
Figure 27. Inverting BuckBoost Regulator
with Delayed startup
D1
1N5822
L1
68
mH
Output
2
4
Feedback
12 V to 25 V
Unregulated
DC Input
Cin
100
mF
/50 V
1
3
5ON/OFF
GN
D
+Vin
12 V @ 700 m A
Regulated
Output
Cout
2200
mF
/16 V
LM257612
C1
0.1
mF
R1
47 k
R2
47 k
Figure 28. Inverting BuckBoost Regulator Shutdown
Circuit Using an Optocoupler
LM2576XX
1
3
5GN
D
ON/OFF
+Vin
R2
47 k
Cin
100
mF
NOTE: This picture does not show the complete circuit.
R1
47 k
R3
470
Shutdown
Input
MOC8101
Vout
Off
On
5.0 V
0
+Vin
With the inverting configuration, the use of the ON/OFF
pin requires some level shifting techniques. This is caused
by the fact, that the ground pin of the converter IC is no
longer at ground. Now, the ON/OFF pin threshold voltage
(1.3 V approximately) has to be related to the negative
output voltage level. There are many different possible shut
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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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