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| 基于L5972D高效直流電源DC－DC參考設計方案 |
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| 文章來(lái)源： 更新時(shí)間：2014/7/21 10:53:00 |
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ST公司的L5972D是一款降壓?jiǎn)纹呻娐饭β书_(kāi)關(guān)型穩壓器，應用于負載直流電流導通大于1.5A的電源設計電路中。該芯片輸出電壓范圍為1.235V至35V。為減少外圍器件及PCB尺寸，內嵌P溝道D-MOS晶體管。內嵌振蕩器開(kāi)關(guān)頻率為250kHz。本文首先介紹芯片的簡(jiǎn)介、特性及應用領(lǐng)域，并給出相應設計方案的設計原理圖、元器件列表及PCB元件布局圖。
The L5972D is a step down monolithic power switching regulator with a minimum switch current limit of 2A so it is able to deliver more than 1.5A DC current to the load depending on the application conditions.
The output voltage can be set from 1.235V to 35V. The device uses an internal P-Channel D-MOS transistor (with a typical Rdson of 250mΩ) as switching element to minimize the size of the external components.
An internal oscillator fixes the switching frequency at 250kHz.Having a minimum input voltage of 4.4V only, it is particularly suitable for 5V bus, available in all computer related applications. Pulse by pulse current limit with the internal frequency modulation offers an effective constant current short circuit protection.
L5972D主要特性：
■ 2A internal switch
■ Operating input voltage from 4.4V to 36V
■ Output voltage adjustable from 1.235V to 35V
■ Low dropout operation: 100% duty cycle
■ 250kHz Internally fixed frequency
■ Voltage feedforward
■ Zero load current operation
■ Internal current limiting
■ Protection against feedback disconnection
■ Thermal shutdown
L5972D應用：
■ Consumer: STB, DVD, TV, VCR, car radio, LCD monitors
■ Networking: XDSL, modems, DC-DC modules
■ Computer: printers, audio/graphic cards, optical storage, hard disk drive
■ Industrial: changers, car battery, DC-DC converters
圖1. L5972D內部方框圖
L5972D方案介紹：
The L5972D is a step-down monolithic power switching regulator capable of delivering up to 2 A at output voltages from 1.235 V to 35 V. The operating input voltage ranges from 4.4 V to 36 V. It has been designed using BCDV technology and the power switching element is implemented through a P-channel DMOS transistor. It does not require a bootstrap capacitor, and the duty cycle can range up to 100%. An internal oscillator fixes the switching frequency at 250 kHz. This minimizes the LC output filter.
Pulse-by-pulse and frequency foldback over-current protection offer effective protection against short-circuit. Other features are voltage feed-forward, protection against feedback disconnection, and thermal shutdown. The device is housed in a thermally improved SO-8 package (with 4 pins connected to GND so that the thermal resistance junction-to-ambient is reduced to approximately one-half compared with a standard SO-8 package.
L5972D方案原理圖：
圖2. L5972D方案原理圖
L5972D方案材料清單：
PCB元件布局圖：
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