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| 基于L5972D高效直流电源DC－DC参考设计方案 |
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| 文章来源： 更新时间：2014/7/21 10:53:00 |
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ST公司的L5972D是一款降压单片集成电路功率开关型稳压器，应用于负载直流电流导通大于1.5A的电源设计电路中。该芯片输出电压范围为1.235V至35V。为减少外围器件及PCB尺寸，内嵌P沟道D-MOS晶体管。内嵌振荡器开关频率为250kHz。本文首先介绍芯片的简介、特性及应用领域，并给出相应设计方案的设计原理图、元器件列表及PCB元件布局图。
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应用：
■ 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
图1. L5972D内部方框图
L5972D方案介绍：
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方案原理图：
图2. L5972D方案原理图
L5972D方案材料清单：
PCB元件布局图：
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