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参数资料
| 型号： | LM2576TV-ADJ |
| 厂商： | MOTOROLA INC |
| 元件分类： | 稳压器 |
| 英文描述： | 3 A SWITCHING REGULATOR, 63 kHz SWITCHING FREQ-MAX, PSFM5 |
| 封装： | TO-220, 5 PIN |
| 文件页数： | 28/28页 |
| 文件大小： | 415K |
| 代理商： | LM2576TV-ADJ |
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LM2576
9
MOTOROLA ANALOG IC DEVICE DATA
PIN FUNCTION DESCRIPTION
Pin
Symbol
Description (Refer to Figure 1)
1
Vin
This pin is the positive input supply for the LM2576 step–down 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 (Cin in Figure 1).
2
Output
This is the emitter of the internal switch. The saturation voltage Vsat 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 non–inverting 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 +Vin) 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 Step–Down Converter which is
the most elementary forward–mode 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:
I
L(on) +
V
in
–Vout ton
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
D
Vin
RLoad
L
Cout
Power
Switch
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:
I
L(off) +
Vout –VD toff
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:
d
+
ton
T
, where T is the period of switching.
For the buck converter with ideal components, the duty
cycle can also be described as:
d
+
Vout
V
in
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
Von(SW)
VD(FWD)
Time
ILoad(AV)
Imin
Ipk
Diode
Power
Switch
Diode
V
oltage
Inductor
Current
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LM2576TV-ADJG | 功能描述:直流/直流开关调节器 3A 1.23-37V ADJ Buck PWM RoHS:否 制造商:International Rectifier 最大输入电压:21 V 开关频率:1.5 MHz 输出电压:0.5 V to 0.86 V 输出电流:4 A 输出端数量: 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:PQFN 4 x 5 |
| LM2576TV-AJD | 制造商:MOTOROLA 制造商全称:Motorola, Inc 功能描述:EASY SWITCHERE⑩ 3.0 A STEP-DOWN VOLTAGE REGULATOR |
| LM2576WT | 功能描述:直流/直流开关调节器 3A Step-Down SMPS Regulator (ROHS Compliant) RoHS:否 制造商:International Rectifier 最大输入电压:21 V 开关频率:1.5 MHz 输出电压:0.5 V to 0.86 V 输出电流:4 A 输出端数量: 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:PQFN 4 x 5 |
| LM2576WT L3 | 制造商:Micrel Inc 功能描述:Micrel LM2576WT L3 DC to DC Conversion |
| LM2576WU | 功能描述:直流/直流开关调节器 3A Step-Down SMPS Regulator (ROHS Compliant) RoHS:否 制造商:International Rectifier 最大输入电压:21 V 开关频率:1.5 MHz 输出电压:0.5 V to 0.86 V 输出电流:4 A 输出端数量: 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:PQFN 4 x 5 |
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