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参数资料
| 型号： | LM2575D2T-12R4 |
| 厂商： | ON Semiconductor |
| 文件页数： | 8/28页 |
| 文件大小： | 0K |
| 描述： | IC REG BUCK 12V 1A D2PAK |
| 产品变化通告： | LTB Notification 03/Jan/2008 |
| 标准包装： | 800 |
| 类型： | 降压（降压） |
| 输出类型： | 固定 |
| 输出数： | 1 |
| 输出电压： | 12V |
| 输入电压： | 4.75 V ~ 40 V |
| PWM 型： | 电压模式 |
| 频率 - 开关： | 52kHz |
| 电流 - 输出： | 1A |
| 同步整流器： | 无 |
| 工作温度： | -40°C ~ 125°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | TO-263-6，D²Pak（5 引线+接片），TO-263BA |
| 包装： | 带卷 (TR) |
| 供应商设备封装： | D2PAK-5 |
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LM2575, NCV2575
PIN FUNCTION DESCRIPTION
Pin
1
2
3
4
5
Symbol
V in
Output
GND
Feedback
ON/OFF
Description (Refer to Figure 1)
This pin is the positive input supply for the LM2575 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 (C in in Figure 1).
This is the emitter of the internal switch. The saturation voltage V sat of this output switch is typically 1.0 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.
Circuit ground pin. See the information about the printed circuit board layout.
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 LM2575 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.
It allows the switching regulator circuit to be shut down using logic level signals, thus dropping the total
input supply current to approximately 80 m A. The input 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 connected to ground, the regulator will be in the “on” condition.
DESIGN PROCEDURE
Buck Converter Basics
The LM2575 is a “Buck” or Step ? Down Converter which
is the most elementary forward ? mode converter. Its basic
schematic can be seen in Figure 15.
current loop. This removes the stored energy from the
inductor.
The inductor current during this time is:
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.
I
L(off)
+
V
out
V
L
D
t
off
V out t on
in
L(on)
L
d + on , where T is the period of switching.
d + out
in
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:
V
I +
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.
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:
t
T
For the buck converter with ideal components, the duty
cycle can also be described as:
V
V
Figure 16 shows the buck converter idealized waveforms
of the catch diode voltage and the inductor current.
Power
Switch
L
V out
V in
D1
C out
R Load
Figure 15. 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 catch dioded. Current now
flows through the catch diode thus maintaining the load
http://onsemi.com
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LM2575D2T-12R4G | 功能描述:直流/直流开关调节器 12V 1A 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 |
| LM2575D2T-15 | 制造商:MOTOROLA 制造商全称:Motorola, Inc 功能描述:EASY SWITCHERE⑩ 1.0 A STEP-DOWN VOLTAGE REGULATOR |
| LM2575D2T-15R | 制造商:未知厂家 制造商全称:未知厂家 功能描述:1.0 A Adjustable Output Voltage Step-Down Switching Regulator(244.52 k) |
| LM2575D2T-15R4 | 功能描述:直流/直流开关调节器 15V 1A 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 |
| LM2575D2T-15R4G | 功能描述:直流/直流开关调节器 15V 1A 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 |
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