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參數(shù)資料
| 型號(hào)： | LM2576D2T-12 |
| 廠商： | MOTOROLA INC |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | EASY SWITCHERE⑩ 3.0 A STEP-DOWN VOLTAGE REGULATOR |
| 中文描述： | 3 A SWITCHING REGULATOR, 63 kHz SWITCHING FREQ-MAX, PSSO5 |
| 封裝： | PLASTIC, D2PAK-5 |
| 文件頁數(shù)： | 19/26頁 |
| 文件大?。?/td> | 278K |
| 代理商： | LM2576D2T-12 |
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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 C
in
.
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 C
out
.
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 F).
The recommended range of inductor values for the
inverting converter design is between 68 H and 220 H. 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
|VO|
Vin
|VO|xfosc
, and fosc
52 kHz.
Ipeak
ILoad(Vin
|VO|)
Vin
Vinx ton
2L1
Under normal continuous inductor current operating
conditions, the worst case occurs when V
in
is minimal.
Figure 27. Inverting BuckBoost Regulator
with Delayed startup
D1
1N5822
L1
68 H
Output
2
4
Feedback
12 V to 25 V
Unregulated
DC Input
C
in
100 F
/50 V
1
3
5
ON/OFF
GN
D
+V
in
12 V @ 700 m A
Regulated
Output
C
out
2200 F
/16 V
LM257612
C1
0.1 F
R1
47 k
R2
47 k
Figure 28. Inverting BuckBoost Regulator Shutdown
Circuit Using an Optocoupler
LM2576XX
1
3
5
GN
D
ON/OFF
+V
in
R2
47 k
C
in
100 F
NOTE: This picture does not show the complete circuit.
R1
47 k
R3
470
Shutdown
Input
MOC8101
V
out
Off
On
5.0 V
0
+V
in
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
down methods, two of them are shown in Figures 28
and
29.
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| LM2576R | 3.0A, 15V, Step-Down Switching Regulator |
| LM2577S-12 | Pressure Transducer, Series 19 mm, Uncompensated, Pressure Range: 0 psi to 100 psi, Absolute, flush mount, 10 Vdc excitation |
| LM2577N-ADJ | Pressure Transducer, Series 19 mm, Compensated, Pressure Range: 0 psi to 200 psi, Absolute, flush mount with flange, 10 Vdc excitation |
| LM2577N-15 | Pressure Transducer, Series 19 mm, Compensated, Pressure Range: 0 psi to 200 psi, Absolute, flush mount, 10 Vdc excitation |
| LM2577N-12 | SIMPLE SWITCHER Step-Up Voltage Regulator |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LM2576D2T-15 | 制造商:MOTOROLA 制造商全稱:Motorola, Inc 功能描述:EASY SWITCHERE⑩ 3.0 A STEP-DOWN VOLTAGE REGULATOR |
| LM2576D2T-15G | 功能描述:直流/直流開關(guān)調(diào)節(jié)器 15V 3A Buck PWM RoHS:否 制造商:International Rectifier 最大輸入電壓:21 V 開關(guān)頻率:1.5 MHz 輸出電壓:0.5 V to 0.86 V 輸出電流:4 A 輸出端數(shù)量: 最大工作溫度: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:PQFN 4 x 5 |
| LM2576D2T-3.3 | 功能描述:直流/直流開關(guān)調(diào)節(jié)器 3.3V 3A Buck PWM RoHS:否 制造商:International Rectifier 最大輸入電壓:21 V 開關(guān)頻率:1.5 MHz 輸出電壓:0.5 V to 0.86 V 輸出電流:4 A 輸出端數(shù)量: 最大工作溫度: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:PQFN 4 x 5 |
| LM2576D2T-3.3G | 功能描述:直流/直流開關(guān)調(diào)節(jié)器 3.3V 3A Buck PWM RoHS:否 制造商:International Rectifier 最大輸入電壓:21 V 開關(guān)頻率:1.5 MHz 輸出電壓:0.5 V to 0.86 V 輸出電流:4 A 輸出端數(shù)量: 最大工作溫度: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:PQFN 4 x 5 |
| LM2576D2T-5 | 制造商:MOTOROLA 制造商全稱:Motorola, Inc 功能描述:Easy Switcher 3.0A Step-Down Voltage Regulator |
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