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参数资料
| 型号： | LM5000-3MTCX/NOPB |
| 厂商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分类： | 稳压器 |
| 英文描述： | 2.7 A SWITCHING REGULATOR, 840 kHz SWITCHING FREQ-MAX, PDSO16 |
| 封装： | TSSOP-16 |
| 文件页数： | 5/18页 |
| 文件大小： | 388K |
| 代理商： | LM5000-3MTCX/NOPB |
OUTPUT VOLTAGE LIMITATIONS
The maximum output voltage of a boost regulator is the max-
imum switch voltage minus a diode drop. In a flyback regula-
tor, the maximum output voltage is determined by the turns
ratio, N, and the duty cycle, D, by the equation:
V
OUT ≈ N × VIN × D/(1 D)
The duty cycle of a flyback regulator is determined by the fol-
lowing equation:
Theoretically, the maximum output voltage can be as large as
desired—just keep increasing the turns ratio of the trans-
former. However, there exists some physical limitations that
prevent the turns ratio, and thus the output voltage, from in-
creasing to infinity. The physical limitations are capacitances
and inductances in the LM5000 switch, the output diode(s),
and the transformer—such as reverse recovery time of the
output diode (mentioned above).
INPUT LINE CONDITIONING
A small, low-pass RC filter should be used at the input pin of
the LM5000 if the input voltage has an unusually large amount
of transient noise. Additionally, the RC filter can reduce the
dissipation within the device when the input voltage is high.
Flyback Regulator Operation
The LM5000 is ideally suited for use in the flyback regulator
topology. The flyback regulator can produce a single output
voltage, or multiple output voltages.
The operation of a flyback regulator is as follows: When the
switch is on, current flows through the primary winding of the
transformer, T1, storing energy in the magnetic field of the
transformer. Note that the primary and secondary windings
are out of phase, so no current flows through the secondary
when current flows through the primary. When the switch
turns off, the magnetic field collapses, reversing the voltage
polarity of the primary and secondary windings. Now rectifier
D5 is forward biased and current flows through it, releasing
the energy stored in the transformer. This produces voltage
at the output.
The output voltage is controlled by modulating the peak
switch current. This is done by feeding back a portion of the
output voltage to the error amp, which amplifies the difference
between the feedback voltage and a 1.259V reference. The
error amp output voltage is compared to a ramp voltage pro-
portional to the switch current (i.e., inductor current during the
switch on time). The comparator terminates the switch on time
when the two voltages are equal, thereby controlling the peak
switch current to maintain a constant output voltage.
20031972
FIGURE 5. LM5000 Flyback Converter
13
www.national.com
LM5000
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LM5000-3MYC | 制造商:Texas Instruments 功能描述: |
| LM5000EP | 制造商:NSC 制造商全称:National Semiconductor 功能描述:Enhanced Plastic High Voltage Switch Mode Regulator |
| LM5000EVAL | 功能描述:电源管理IC开发工具 LM5000 EVAL UNIT RoHS:否 制造商:Maxim Integrated 产品:Evaluation Kits 类型:Battery Management 工具用于评估:MAX17710GB 输入电压: 输出电压:1.8 V |
| LM5000EVAL/NOPB | 功能描述:EVALUATION BOARD FOR LM5000 RoHS:是 类别:编程器，开发系统 >> 评估板 - DC/DC 与 AC/DC（离线）SMPS 系列:- 产品培训模块:Obsolescence Mitigation Program 标准包装:1 系列:True Shutdown™ 主要目的:DC/DC，步升 输出及类型:1，非隔离 功率 - 输出:- 输出电压:- 电流 - 输出:1A 输入电压:2.5 V ~ 5.5 V 稳压器拓扑结构:升压 频率 - 开关:3MHz 板类型:完全填充 已供物品:板 已用 IC / 零件:MAX8969 |
| LM5000SD-3 | 功能描述:直流/直流开关转换器 RoHS:否 制造商:STMicroelectronics 最大输入电压:4.5 V 开关频率:1.5 MHz 输出电压:4.6 V 输出电流:250 mA 输出端数量:2 最大工作温度:+ 85 C 安装风格:SMD/SMT |
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