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參數(shù)資料
| 型號： | 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)： | 9/26頁 |
| 文件大?。?/td> | 278K |
| 代理商： | LM2576D2T-12 |
LM2576
http://onsemi.com
9
PIN FUNCTION DESCRIPTION
Pin
Symbol
Description (Refer to Figure 1)
1
V
in
This pin is the positive input supply for the LM2576 stepdown switching regulator. In order to minimize voltage
transients and to supply the switching currents needed by the regulator, a suitable input bypass capacitor must be
present (C
in
in Figure 1).
2
Output
This is the emitter of the internal switch. The saturation voltage V
sat
of this output switch is typically 1.5 V. It should
be kept in mind that the PCB area connected to this pin should be kept to a minimum in order to minimize coupling
to sensitive circuitry.
3
GND
Circuit ground pin. See the information about the printed circuit board layout.
4
Feedback
This pin senses regulated output voltage to complete the feedback loop. The signal is divided by the internal resistor
divider network R2, R1 and applied to the noninverting input of the internal error amplifier. In the Adjustable version
of the LM2576 switching regulator this pin is the direct input of the error amplifier and the resistor network R2, R1 is
connected externally to allow programming of the output voltage.
5
ON/OFF
It allows the switching regulator circuit to be shut down using logic level signals, thus dropping the total input supply
current to approximately 80 A. The threshold voltage is typically 1.4 V. Applying a voltage above this value (up to
+V
in
) shuts the regulator off. If the voltage applied to this pin is lower than 1.4 V or if this pin is left open, the
regulator will be in the “on” condition.
DESIGN PROCEDURE
Buck Converter Basics
The LM2576 is a “Buck” or StepDown Converter which
is the most elementary forwardmode converter. Its basic
schematic can be seen in
Figure 16.
The operation of this regulator topology has two distinct
time periods. The first one occurs when the series switch is
on, the input voltage is connected to the input of the inductor.
The output of the inductor is the output voltage, and the
rectifier (or catch diode) is reverse biased. During this
period, since there is a constant voltage source connected
across the inductor, the inductor current begins to linearly
ramp upwards, as described by the following equation:
IL(on)
Vin– Voutton
L
During this “on” period, energy is stored within the core
material in the form of magnetic flux. If the inductor is
properly designed, there is sufficient energy stored to carry
the requirements of the load during the “off” period.
Figure 16. Basic Buck Converter
The next period is the “off” period of the power switch.
When the power switch turns off, the voltage across the
inductor reverses its polarity and is clamped at one diode
voltage drop below ground by the catch diode. The current
now flows through the catch diode thus maintaining the load
current loop. This removes the stored energy from the
inductor. The inductor current during this time is:
D
V
in
R
Load
L
C
out
Power
Switch
IL(off)
Vout– VDtoff
L
This period ends when the power switch is once again
turned on. Regulation of the converter is accomplished by
varying the duty cycle of the power switch. It is possible to
describe the duty cycle as follows:
ton
T, where T is the period of switching.
For the buck converter with ideal components, the duty
cycle can also be described as:
Vout
d
d
Vin
Figure 17 shows the buck converter, idealized waveforms
of the catch diode voltage and the inductor current.
Power
Switch
Figure 17. Buck Converter Idealized Waveforms
Power
Switch
Off
Power
Switch
Off
Power
Switch
On
Power
Switch
On
V
on(SW)
V
D
(FWD)
Time
Time
I
Load
(AV)
I
min
I
pk
Diode
Diode
Power
Switch
D
I
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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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